Respiratory Tract, Respiratory Apparatus, Ventilatory System
The respiratory system is made up of organs and tissues that help you breathe. The main parts of this system are the airways, the lungs and linked blood vessels, and the muscles that enable breathing. Learn more.
Respiratory System
Image by TheVisualMD
Respiratory System
Respiratory system, worm-eye view
Image by TheVisualMD
Respiratory system, worm-eye view
The group of organs and tissues that help you breathe is know as the respiratory system. The main parts of this system are the airways the lungs, and linked blood vessels, and the muscles that enable breathing. This system acts to bring in air from outside the body, filter it, moisten it, warm it and bring it into contact with the small capillaries of the circulatory system. The respiratory system works with the circulatory system to deliver oxygen to tissues throughout body and remove carbon dioxide waste.
Image by TheVisualMD
Respiratory System
The respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity, which helps to warm and humidify incoming air, while removing debris and pathogens. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity; the oropharynx, which borders the nasopharynx and the oral cavity; and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli.
The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps pathogens and debris, whereas beating cilia move the mucus superiorly toward the throat, where it is swallowed. As the bronchioles become smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. This is a blood-air barrier through which gas exchange occurs by simple diffusion.
The major organs of the respiratory system function primarily to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. Portions of the respiratory system are also used for non-vital functions, such as sensing odors, speech production, and for straining, such as during childbirth or coughing (image).
Functionally, the respiratory system can be divided into a conducting zone and a respiratory zone. The conducting zone of the respiratory system includes the organs and structures not directly involved in gas exchange. The gas exchange occurs in the respiratory zone .
Source: CNX OpenStax
Additional Materials (23)
Larynx and Upper Respiratory Tract
Larynx and Upper Respiratory Tract
Image by TheVisualMD
Respiratory System: Muscles – Respiratory Medicine | Medical Education Videos
Video by Lecturio Medical/YouTube
The respiratory center | Respiratory system physiology | NCLEX-RN | Khan Academy
Video by khanacademymedicine/YouTube
Respiratory | Regulation of Breathing: Respiratory Centers: Part 1
Respiratory System Physiology - Ventilation and Perfusion (V:Q Ratio) Physiology
Armando Hasudungan/YouTube
1:03:00
Anatomy and Physiology of Respiratory System
New Anatomy and Physiology Video/YouTube
9:44
Respiratory System And Lungs Anatomy
Animated Anatomy/YouTube
15:48
Respiratory System - Overview
Armando Hasudungan/YouTube
9:22
Respiratory System, Part 1: Crash Course A&P #31
CrashCourse/YouTube
1:29
The Respiratory System | Merck Manual Consumer Version
Merck Manuals/YouTube
2:06
Respiratory Tree Anatomy - Conducting Zone & Respiratory Zone
USMLEFastTrack/YouTube
1:54
Biology Help: The Respiratory System - Gas Exchange In The Alveoli Explained In 2 Minutes!!
5MinuteSchool/YouTube
5:16
Overview of the Respiratory System, Animation
Alila Medical Media/YouTube
10:19
Lungs (Structures, Coverings and Recesses) - Respiratory System Anatomy
Meditay/YouTube
3:37
Respiratory System Introduction - Part 1 (Nose to Bronchi) - 3D Anatomy Tutorial
AnatomyZone/YouTube
7:37
Respiratory System Introduction - Part 2 (Bronchial Tree and Lungs) - 3D Anatomy Tutorial
AnatomyZone/YouTube
6:06
Neurovascular bundle | Respiratory system diseases | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
7:45
O2 and CO2 solubility | Respiratory system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
8:39
Henry's law | Respiratory system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
7:59
Alveolar gas equation - part 1 | Respiratory system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
7:06
Alveolar gas equation - part 2 | Respiratory system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
The Respiratory System Introduction
Swimmer with Visible Lung Coming Up for Air
Image by TheVisualMD
Swimmer with Visible Lung Coming Up for Air
When we inhale, oxygen and other gases travel through the nasal or oral cavities, then to the pharynx and down the trachea and into either the left or right bronchi to the lungs. There, oxygen passes through the porous walls of tiny air sacs called alveoli and into the surrounding capillaries. After the RBCs deliver the oxygen to the body's tissues, they pick up carbon dioxide and carry it back to the lungs where the process is reversed and the carbon dioxide is expelled when we exhale. This miracle of molecular transportation is performed with each of the roughly 20,000 breaths we take every day.
Image by TheVisualMD
The Respiratory System Introduction
Mountain Climbers
The thin air at high elevations can strain the human respiratory system. (credit: “bortescristian”/flickr.com)
Hold your breath. Really! See how long you can hold your breath as you continue reading…How long can you do it? Chances are you are feeling uncomfortable already. A typical human cannot survive without breathing for more than 3 minutes, and even if you wanted to hold your breath longer, your autonomic nervous system would take control. This is because every cell in the body needs to run the oxidative stages of cellular respiration, the process by which energy is produced in the form of adenosine triphosphate (ATP). For oxidative phosphorylation to occur, oxygen is used as a reactant and carbon dioxide is released as a waste product. You may be surprised to learn that although oxygen is a critical need for cells, it is actually the accumulation of carbon dioxide that primarily drives your need to breathe. Carbon dioxide is exhaled and oxygen is inhaled through the respiratory system, which includes muscles to move air into and out of the lungs, passageways through which air moves, and microscopic gas exchange surfaces covered by capillaries. The circulatory system transports gases from the lungs to tissues throughout the body and vice versa. A variety of diseases can affect the respiratory system, such as asthma, emphysema, chronic obstruction pulmonary disorder (COPD), and lung cancer. All of these conditions affect the gas exchange process and result in labored breathing and other difficulties.
Source: CNX OpenStax
Additional Materials (7)
Larynx - Ligaments, Membranes, Vocal Cords - 3D Anatomy Tutorial
Video by AnatomyZone/YouTube
Anatomy of Larynx: Membranes and Muscles by Zoe Kirkham-Mowbray (Part 2 of 3)
Video by Dundee Tilt/Vimeo
This browser does not support the video element.
Human Body Revealing Alveoli Within Lung
Camera zooms in on visible human with arms extended upwards, begins with only the circulatory system, lungs, and kidneys showing The skeleton fades in, and the lungs are contracting and expanding to demonstrate the movements associated with breathing. The camera then zooms into the lungs to focus on the alveoli within
Video by TheVisualMD
Male Thorax with Visible Trachea and Lung
3D visualization of an anterior oblique view of the trachea and the lungs, reconstructed from scanned human data. The bifurcation of the trachea and the extensive branching of the right and left bronchi are revealed. The respiratory system consists of branching tubes that work to bring oxygen from the air to the organs and tissues of the body, and to expel carbon dioxide wastes from the body to the air. The bronchial tree is a system of airways in which the \"trunk\" is the windpipe and the \"branches\" are the subdividing passages that permeate the lungs. While the rest of the system works as a kind of accordion pump, the structures of the bronchial network split and split again until they are so numerous and so thin at their membranous tips that gas molecules can cross over to the blood through a network of capillaries that, laid end to end, would measure more than 1,000 miles.
Image by TheVisualMD
Male Thorax with Visible Lung and Heart
3D visualization of an anterior view of the lungs and heart reconstructed from scanned human data. The cone-shaped lungs occupy most of the thoracic cavity. Each lung is suspended in its own pleural cavity and connected to the mediastinum (which houses the heart) by its root which is made up of vascular and bronchial attachments. The anterior, lateral and posterior surfaces of the lung are in close contact with the ribs and form a continuously curving surface called the costal surface. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
Thorax with visible Lung and Heart
3D visualization of a posterior view of the lungs and heart reconstructed from scanned human data. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
Thorax with Heart and Lung
3D visualization of an anterior view of the lungs and heart reconstructed from scanned human data. The cone-shaped lungs occupy most of the thoracic cavity. Each lung is suspended in its own pleural cavity and connected to the mediastinum (which houses the heart) by its root which is made up of vascular and bronchial attachments. The anterior, lateral and posterior surfaces of the lung are in close contact with the ribs and form a continuously curving surface called the costal surface. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
13:15
Larynx - Ligaments, Membranes, Vocal Cords - 3D Anatomy Tutorial
AnatomyZone/YouTube
2:45
Anatomy of Larynx: Membranes and Muscles by Zoe Kirkham-Mowbray (Part 2 of 3)
Dundee Tilt/Vimeo
0:15
Human Body Revealing Alveoli Within Lung
TheVisualMD
Male Thorax with Visible Trachea and Lung
TheVisualMD
Male Thorax with Visible Lung and Heart
TheVisualMD
Thorax with visible Lung and Heart
TheVisualMD
Thorax with Heart and Lung
TheVisualMD
Review: Introduction to the Respiratory System
Lungs, Bronchi and Bronchioles / Bronchioles and Arteries in Lungs within Male Chest / Bronchi and Bronchioles in Lungs within Male Chest
Lungs, Bronchi and Bronchioles
Interactive by TheVisualMD
Lungs, Bronchi and Bronchioles / Bronchioles and Arteries in Lungs within Male Chest / Bronchi and Bronchioles in Lungs within Male Chest
Lungs, Bronchi and Bronchioles
1) Lungs, Bronchi and Bronchioles
2) Bronchioles and Arteries
3) Bronchi and Bronchioles
When you inhale, air passes down the back of your throat, past your vocal cords, and into your windpipe, or trachea. Your trachea divides into twin air pipes (one for each lung) called the bronchi. Much the way in which a tree branches, the bronchi continue to divide into smaller air passages called bronchioles. Collectively, these air passages are known as the airways. The bronchioles continue to branch until they become extremely narrow-the small airways are less than 2 micrometers in diameter! They end in microscopic air sacs called alveoli. Your lungs contain about 500 million alveoli.
Interactive by TheVisualMD
Review: Introduction to the Respiratory System
The entire process of respiration includes ventilation, external respiration, transport of gases, internal respiration, and cellular respiration.
The three pressures responsible for pulmonary ventilation are atmospheric pressure, intraalveolar pressure, and intrapleural pressure.
A spirometer is used to measure respiratory volumes and capacities. These measurements provide useful information about the condition of the lungs.
The frontal, maxillary, ethmoidal, and sphenoidal sinuses are air-filled cavities that open into the nasal cavity.
The pharynx, commonly called the throat, is a passageway that extends from the base of the skull to the level of the sixth cervical vertebra.
The larynx, commonly called the voice box, is the passageway for air between the pharynx above and the trachea below.
The trachea, commonly called the windpipe, is the main airway to the lungs.
The trachea divides into the right and left primary bronchi, which branch into smaller and smaller passageways until they terminate in tiny air sacs called alveoli.
The two lungs contain all the components of the bronchial tree beyond the primary bronchi.
The right lung is shorter, broader, and is divided into three lobes.
The left lung is longer, narrower, and is divided into two lobes.
Source: National Cancer Institute (NCI)
Additional Materials (11)
Lung vasculature
Lung vasculature
1
2
Transparent Normal Lungs
Interactive by TheVisualMD
Lung Vasculature
Image by TheVisualMD
4D CT of lung
Spiral 4DCT Lung (Lateral) - Low-pitch spiral 4D CT of lung with artifacts reduced by optimized projection binning
Image by René Werner, Christian Hofmann, Eike Mücke and Tobias Gauer
Child Respiratory Problems
Child Respiratory Problems
Image by TheVisualMD
Upper Respiratory Cross section of Heart and lung, diaphragm, and trachea
3D visualization of an anterior view of the muscles involved in respiration. The primary job of the thorax is to promote movements necessary for breathing. Three muscles of the thorax assist in this function; the external intercostals, internal intercostals and diaphragm. The intercostals do the job of lifting the ribs up and pulling them outward, which in turn enlarges the lungs. As the lungs expand, the pressure inside them is reduced, and they suck in air. During extreme inhalation, the neck muscles also contract. During inhalation, the diaphragm contracts and pushes downward; during exhalation, it relaxes and is pushed up into a dome shape by the lower digestive organs, compressing the lungs. As pressure rises in the chest cavity, exhale occurs, pressure is equalized and the cycle restarts.
Image by TheVisualMD
Human Respiratory System
Human Respiratory System
Image by TheVisualMD
Respiration
Video by 7activestudio/YouTube
Respiratory Tree Anatomy - Conducting Zone & Respiratory Zone
Video by USMLEFastTrack/YouTube
Respiratory System
Line drawing showing nasal cavity, pharynx, larynx, trachea, pleura, bronchi, etc.
Image by National Cancer Institute / Unknown Illustrator
Respiratory System
Major Respiratory Organs
Image by OpenStax College
Respiratory System
The tubular and cavernous organs and structures, by means of which pulmonary ventilation and gas exchange between ambient air and the blood are brought about. (NCBI/NLM/NIH)
Image by Bryan Brandenburg
Transparent Normal Lungs
TheVisualMD
Lung Vasculature
TheVisualMD
4D CT of lung
René Werner, Christian Hofmann, Eike Mücke and Tobias Gauer
Child Respiratory Problems
TheVisualMD
Upper Respiratory Cross section of Heart and lung, diaphragm, and trachea
TheVisualMD
Human Respiratory System
TheVisualMD
4:00
Respiration
7activestudio/YouTube
2:06
Respiratory Tree Anatomy - Conducting Zone & Respiratory Zone
USMLEFastTrack/YouTube
Respiratory System
National Cancer Institute / Unknown Illustrator
Respiratory System
OpenStax College
Respiratory System
Bryan Brandenburg
Anatomy of the Respiratory Tract
Respiratory System of Male and Female
Image by TheVisualMD
Respiratory System of Male and Female
Medical visualization of the respiratory systems of a female and male. The translucent skin of both the male and female reveals the nasal cavity, trachea and the lungs.
Image by TheVisualMD
Anatomy of the Upper and Lower Respiratory Tracts
The respiratory system can be conceptually divided into upper and lower regions at the point of the epiglottis, the structure that seals off the lower respiratory system from the pharynx during swallowing (Figure). The upper respiratory system is in direct contact with the external environment. The nares (or nostrils) are the external openings of the nose that lead back into the nasal cavity, a large air-filled space behind the nares. These anatomical sites constitute the primary opening and first section of the respiratory tract, respectively. The nasal cavity is lined with hairs that trap large particles, like dust and pollen, and prevent their access to deeper tissues. The nasal cavity is also lined with a mucous membrane and Bowman’s glands that produce mucus to help trap particles and microorganisms for removal. The nasal cavity is connected to several other air-filled spaces. The sinuses, a set of four, paired small cavities in the skull, communicate with the nasal cavity through a series of small openings. The nasopharynx is part of the upper throat extending from the posterior nasal cavity. The nasopharynx carries air inhaled through the nose. The middle ear is connected to the nasopharynx through the eustachian tube. The middle ear is separated from the outer ear by the tympanic membrane, or ear drum. And finally, the lacrimal glands drain to the nasal cavity through the nasolacrimal ducts (tear ducts). The open connections between these sites allow microorganisms to move from the nasal cavity to the sinuses, middle ears (and back), and down into the lower respiratory tract from the nasopharynx.
The oral cavity is a secondary opening for the respiratory tract. The oral and nasal cavities connect through the fauces to the pharynx, or throat. The pharynx can be divided into three regions: the nasopharynx, the oropharynx, and the laryngopharynx. Air inhaled through the mouth does not pass through the nasopharynx; it proceeds first through the oropharynx and then through the laryngopharynx. The palatine tonsils, which consist of lymphoid tissue, are located within the oropharynx. The laryngopharynx, the last portion of the pharynx, connects to the larynx, which contains the vocal fold (Figure).
(a) The ear is connected to the upper respiratory tract by the eustachian tube, which opens to the nasopharynx. (b) The structures of the upper respiratory tract.
Anatomy of the Lower Respiratory System
The lower respiratory system begins below the epiglottis in the larynx or voice box (Figure). The trachea, or windpipe, is a cartilaginous tube extending from the larynx that provides an unobstructed path for air to reach the lungs. The trachea bifurcates into the left and right bronchi as it reaches the lungs. These paths branch repeatedly to form smaller and more extensive networks of tubes, the bronchioles. The terminal bronchioles formed in this tree-like network end in cul-de-sacs called the alveoli. These structures are surrounded by capillary networks and are the site of gas exchange in the respiratory system. Human lungs contain on the order of 400,000,000 alveoli. The outer surface of the lungs is protected with a double-layered pleural membrane. This structure protects the lungs and provides lubrication to permit the lungs to move easily during respiration.
The structures of the lower respiratory tract are identified in this illustration. (credit: modification of work by National Cancer Institute)
In summary:
The respiratory tract is divided into upper and lower regions at the epiglottis.
Air enters the upper respiratory tract through the nasal cavity and mouth, which both lead to the pharynx. The lower respiratory tract extends from the larynx into the trachea before branching into the bronchi, which divide further to form the bronchioles, which terminate in alveoli, where gas exchange occurs.
Source: CNX OpenStax
Additional Materials (18)
Respiratory System
3D visualization of an anterior view of the respiratory system of an adult male, reconstructed from scanned human data. The upper respiratory system, including coronal sections of the paranasal sinuses and the oral cavity, are visible through areas of transparent skin on the face. The respiratory system consists of branching tubes that work to bring oxygen from the air to the organs and tissues of the body, and to expell carbon dioxide wastes from the body to the air. The bronchial tree is a system of airways in which the \"trunk\" is the windpipe and the \"branches\" are the subdividing passages that permeate the lungs. While the rest of the system works as a kind of accordion pump, the structures of the bronchial network split and split again until they are so numerous and so thin at their membranous tips that gas molecules can cross over to the blood through a network of capillaries that, laid end to end, would measure more than 1,000 miles.
Image by TheVisualMD
Female Nasal passages, Trachea, Lungs and Respiratory System
Female Nasal passages, Trachea, Lungs and Respiratory System
Image by TheVisualMD
Respiratory system, worm-eye view
The group of organs and tissues that help you breathe is know as the respiratory system. The main parts of this system are the airways the lungs, and linked blood vessels, and the muscles that enable breathing. This system acts to bring in air from outside the body, filter it, moisten it, warm it and bring it into contact with the small capillaries of the circulatory system. The respiratory system works with the circulatory system to deliver oxygen to tissues throughout body and remove carbon dioxide waste.
Image by TheVisualMD
Respiratory System, Part 1: Crash Course A&P #31
Video by CrashCourse/YouTube
Respiratory System
Promoting Respiratory Health
Image by TheVisualMD
Respiratory Centers
Respiratory Centers of the Brain
Image by OpenStax College
3D medical animation still showing constricted airways.
3D medical animation still showing bronchial asthma.
Image by Scientific Animations, Inc.
Respiratory Syncytial Virus
Respiratory syncytial virus (RSV) causes infections of the lungs and respiratory tract. It is a common viral respiratory infection that tends to be seasonal, causing community epidemics in young children, older adults, and those whose immune systems are compromised. RSV enters your body through your eyes, nose or mouth. It spreads easily when infectious respiratory secretions, such as those from coughing or sneezing, are inhaled or passed to others through direct contact, such as shaking hands. Currently, there is no vaccine for RSV. A short-term drug therapy that can minimize lower respiratory tract symptoms after infection is given to some high-risk people.
Image by TheVisualMD
Heart pulmonary and great vessels
Heart pulmonary and great vessels
Image by TheVisualMD
Respiratory tract
Caliber of human airway compartments.
Image by Curentec
Male Thorax Showing Trachea and Lung
3D visualization of an anterior view of the lungs and heart reconstructed from scanned human data. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
Male Head Showing Nasal Cavity
Male Head Showing Nasal Cavity : 3D visualization reconstructed from scanned human data of a lateral view of the head featuring the nasal cavity.
Image by TheVisualMD
Bronchitis
Swelling of airways in the lungs produce mucus in the lungs and makes you cough.
Image by CDC
Swimmer with Visible Lung Coming Up for Air
When we inhale, oxygen and other gases travel through the nasal or oral cavities, then to the pharynx and down the trachea and into either the left or right bronchi to the lungs. There, oxygen passes through the porous walls of tiny air sacs called alveoli and into the surrounding capillaries. After the RBCs deliver the oxygen to the body's tissues, they pick up carbon dioxide and carry it back to the lungs where the process is reversed and the carbon dioxide is expelled when we exhale. This miracle of molecular transportation is performed with each of the roughly 20,000 breaths we take every day.
Image by TheVisualMD
Respiratory System
Male Thorax with Visible Trachea and Lung : 3D visualization of an anterior oblique view of the trachea and the lungs, reconstructed from scanned human data. The bifurcation of the trachea and the extensive branching of the right and left bronchi are revealed. The respiratory system consists of branching tubes that work to bring oxygen from the air to the organs and tissues of the body, and to expel carbon dioxide wastes from the body to the air. The bronchial tree is a system of airways in which the "trunk" is the windpipe and the "branches" are the subdividing passages that permeate the lungs. While the rest of the system works as a kind of accordion pump, the structures of the bronchial network split and split again until they are so numerous and so thin at their membranous tips that gas molecules can cross over to the blood through a network of capillaries that, laid end to end, would measure more than 1,000 miles.
Image by TheVisualMD
Thorax with Muscle Involved in Respiration
3D visualization of an anterior view of the muscles involved in respiration. The primary job of the thorax is to promote movements necessary for breathing. Three muscles of the thorax assist in this function; the external intercostals, internal intercostals and diaphragm. The intercostals do the job of lifting the ribs up and pulling them outward, which in turn enlarges the lungs. As the lungs expand, the pressure inside them is reduced, and they suck in air. During extreme inhalation, the neck muscles also contract. During inhalation, the diaphragm contracts and pushes downward; during exhalation, it relaxes and is pushed up into a dome shape by the lower digestive organs, compressing the lungs. As pressure rises in the chest cavity, exhale occurs, pressure is equalized and the cycle restarts.
Image by TheVisualMD
Respiratory Tract
3D visualization of a midsagittal view of the respiratory tract, paranasal sinuses and oral cavity reconstructed from scanned human data. When air is inhaled into the lungs, it flows through large tubes called bronchi, branches into smaller tubes known as bronchioles, and ends up in the thousands of small pouches that are the alveoli. This is where the oxygen is transferred from the air into the bloodstream. Each alveolar sac, or air sac, is surrounded by a bed of capillaries, and the walls between the lung and the capillary are extremely thin. The walls are so delicate, in fact, that the inhaled oxygen can seep from the air sacs to bind to the hemoglobin in the blood, while the carbon dioxide and other waste gasses leave the blood and diffuse into the lungs where they can be exhaled.
Image by TheVisualMD
Respiratory System
TheVisualMD
Female Nasal passages, Trachea, Lungs and Respiratory System
TheVisualMD
Respiratory system, worm-eye view
TheVisualMD
9:22
Respiratory System, Part 1: Crash Course A&P #31
CrashCourse/YouTube
Respiratory System
TheVisualMD
Respiratory Centers
OpenStax College
3D medical animation still showing constricted airways.
Scientific Animations, Inc.
Respiratory Syncytial Virus
TheVisualMD
Heart pulmonary and great vessels
TheVisualMD
Respiratory tract
Curentec
Male Thorax Showing Trachea and Lung
TheVisualMD
Male Head Showing Nasal Cavity
TheVisualMD
Bronchitis
CDC
Swimmer with Visible Lung Coming Up for Air
TheVisualMD
Respiratory System
TheVisualMD
Thorax with Muscle Involved in Respiration
TheVisualMD
Respiratory Tract
TheVisualMD
Defenses and Microbiota of the Respiratory System
Baby Sitting Showing Respiratory System
Image by TheVisualMD
Baby Sitting Showing Respiratory System
A baby's first breath is dramatic for all kinds of reasons, including physiological ones. A protein-lipid combination called surfactant plays a critical role in lung development. Researchers have discovered that nutrients such as vitamin D also play important roles in the healthy development of the infant's respiratory system. One of the most obvious ways that we notice the overall immune health of a baby is through the presence or absence of respiratory infections. Respiratory illness is the leading cause of hospitalization among young children. And when it is severe enough to require hospitalization, respiratory illness greatly increases the risk of childhood asthma.
Image by TheVisualMD
Defenses and Microbiota of the Respiratory System
The inner lining of the respiratory system consists of mucous membranes (Figure) and is protected by multiple immune defenses. The goblet cells within the respiratory epithelium secrete a layer of sticky mucus. The viscosity and acidity of this secretion inhibits microbial attachment to the underlying cells. In addition, the respiratory tract contains ciliated epithelial cells. The beating cilia dislodge and propel the mucus, and any trapped microbes, upward to the epiglottis, where they will be swallowed. Elimination of microbes in this manner is referred to as the mucociliary escalator effect and is an important mechanism that prevents inhaled microorganisms from migrating further into the lower respiratory tract.
The upper respiratory system is under constant surveillance by mucosa-associated lymphoid tissue (MALT), including the adenoids and tonsils. Other mucosal defenses include secreted antibodies (IgA), lysozyme, surfactant, and antimicrobial peptides called defensins. Meanwhile, the lower respiratory tract is protected by alveolar macrophages. These phagocytes efficiently kill any microbes that manage to evade the other defenses. The combined action of these factors renders the lower respiratory tract nearly devoid of colonized microbes.
Normal Microbiota of the Respiratory System
The upper respiratory tract contains an abundant and diverse microbiota. The nasal passages and sinuses are primarily colonized by members of the Firmicutes, Actinobacteria, and Proteobacteria. The most common bacteria identified include Staphylococcus epidermidis, viridans group streptococci (VGS), Corynebacterium spp. (diphtheroids), Propionibacteriumspp., and Haemophilus spp. The oropharynx includes many of the same isolates as the nose and sinuses, with the addition of variable numbers of bacteria like species of Prevotella, Fusobacterium, Moraxella, and Eikenella, as well as some Candidafungal isolates. In addition, many healthy humans asymptomatically carry potential pathogens in the upper respiratory tract. As much as 20% of the population carry Staphylococcus aureus in their nostrils. The pharynx, too, can be colonized with pathogenic strains of Streptococcus, Haemophilus, and Neisseria.
The lower respiratory tract, by contrast, is scantily populated with microbes. Of the organisms identified in the lower respiratory tract, species of Pseudomonas, Streptococcus, Prevotella, Fusobacterium, and Veillonella are the most common. It is not clear at this time if these small populations of bacteria constitute a normal microbiota or if they are transients.
Many members of the respiratory system’s normal microbiota are opportunistic pathogens. To proliferate and cause host damage, they first must overcome the immune defenses of respiratory tissues. Many mucosal pathogens produce virulence factors such as adhesins that mediate attachment to host epithelial cells, or polysaccharide capsules that allow microbes to evade phagocytosis. The endotoxins of gram-negative bacteria can stimulate a strong inflammatory response that damages respiratory cells. Other pathogens produce exotoxins, and still others have the ability to survive within the host cells. Once an infection of the respiratory tract is established, it tends to impair the mucociliary escalator, limiting the body’s ability to expel the invading microbes, thus making it easier for pathogens to multiply and spread.
Vaccines have been developed for many of the most serious bacterial and viral pathogens. Several of the most important respiratory pathogens and their vaccines, if available, are summarized in Table. Components of these vaccines will be explained later in the chapter.
Microbial diseases of the respiratory system typically result in an acute inflammatory response. These infections can be grouped by the location affected and have names ending in “itis”, which literally means inflammation of. For instance, rhinitis is an inflammation of the nasal cavities, often characteristic of the common cold. Rhinitis may also be associated with hay fever allergies or other irritants. Inflammation of the sinuses is called sinusitis inflammation of the ear is called otitis. Otitis media is an inflammation of the middle ear. A variety of microbes can cause pharyngitis, commonly known as a sore throat. An inflammation of the larynx is called laryngitis. The resulting inflammation may interfere with vocal cord function, causing voice loss. When tonsils are inflamed, it is called tonsillitis. Chronic cases of tonsillitis may be treated surgically with tonsillectomy. More rarely, the epiglottis can be infected, a condition called epiglottitis. In the lower respiratory system, the inflammation of the bronchial tubes results in bronchitis. Most serious of all is pneumonia, in which the alveoli in the lungs are infected and become inflamed. Pus and edema accumulate and fill the alveoli with fluids (called consolidations). This reduces the lungs’ ability to exchange gases and often results in a productive cough expelling phlegm and mucus. Cases of pneumonia can range from mild to life-threatening, and remain an important cause of mortality in the very young and very old.
Key Concepts and Summary
The upper respiratory tract is colonized by an extensive and diverse normal microbiota, many of which are potential pathogens. Few microbial inhabitants have been found in the lower respiratory tract, and these may be transients.
Members of the normal microbiota may cause opportunistic infections, using a variety of strategies to overcome the innate nonspecific defenses (including the mucociliary escalator) and adaptive specific defenses of the respiratory system.
Effective vaccines are available for many common respiratory pathogens, both bacterial and viral.
Most respiratory infections result in inflammation of the infected tissues; these conditions are given names ending in -itis, such as rhinitis, sinusitis, otitis, pharyngitis, and bronchitis.
Source: CNX OpenStax
Additional Materials (1)
Lecture: Part 1 - Bacterial Diseases of the Respiratory System
Video by Mind Over Microbiology/YouTube
15:55
Lecture: Part 1 - Bacterial Diseases of the Respiratory System
Mind Over Microbiology/YouTube
Mechanics of Ventilation
Thorax with Muscle Involved in Respiration
Image by TheVisualMD
Thorax with Muscle Involved in Respiration
3D visualization of an inferior view of the muscles involved in respiration. The primary job of the thorax is to promote movements necessary for breathing. Three muscles of the thorax assist in this function; the external intercostals, internal intercostals and diaphragm. The intercostals do the job of lifting the ribs up and pulling them outward, which in turn enlarges the lungs. As the lungs expand, the pressure inside them is reduced, and they suck in air. During extreme inhalation, the neck muscles also contract. During inhalation, the diaphragm contracts and pushes downward; during exhalation, it relaxes and is pushed up into a dome shape by the lower digestive organs, compressing the lungs. As pressure rises in the chest cavity, exhalation occurs, pressure is equalized and the cycle restarts.
Image by TheVisualMD
Mechanics of Ventilation
Ventilation, or breathing, is the movement of air through the conducting passages between the atmosphere and the lungs. The air moves through the passages because of pressure gradients that are produced by contraction of the diaphragm and thoracic muscles.
Pulmonary ventilation
Pulmonary ventilation is commonly referred to as breathing. It is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation). Air flows because of pressure differences between the atmosphere and the gases inside the lungs.
Air, like other gases, flows from a region with higher pressure to a region with lower pressure. Muscular breathing movements and recoil of elastic tissues create the changes in pressure that result in ventilation. Pulmonary ventilation involves three different pressures:
Atmospheric pressure
Intraalveolar (intrapulmonary) pressure
Intrapleural pressure
Atmospheric pressure is the pressure of the air outside the body. Intraalveolar pressure is the pressure inside the alveoli of the lungs. Intrapleural pressure is the pressure within the pleural cavity. These three pressures are responsible for pulmonary ventilation.
Inspiration
Inspiration (inhalation) is the process of taking air into the lungs. It is the active phase of ventilation because it is the result of muscle contraction. During inspiration, the diaphragm contracts and the thoracic cavity increases in volume. This decreases the intraalveolar pressure so that air flows into the lungs. Inspiration draws air into the lungs.
Expiration
Expiration (exhalation) is the process of letting air out of the lungs during the breathing cycle. During expiration, the relaxation of the diaphragm and elastic recoil of tissue decreases the thoracic volume and increases the intraalveolar pressure. Expiration pushes air out of the lungs.
Source: National Cancer Institute (NCI)
Additional Materials (10)
Thorax with Muscle Involved in Respiration
3D visualization of an anterior view of the muscles involved in respiration. The primary job of the thorax is to promote movements necessary for breathing. Three muscles of the thorax assist in this function; the external intercostals, internal intercostals and diaphragm. The intercostals do the job of lifting the ribs up and pulling them outward, which in turn enlarges the lungs. As the lungs expand, the pressure inside them is reduced, and they suck in air. During extreme inhalation, the neck muscles also contract. During inhalation, the diaphragm contracts and pushes downward; during exhalation, it relaxes and is pushed up into a dome shape by the lower digestive organs, compressing the lungs. As pressure rises in the chest cavity, exhale occurs, pressure is equalized and the cycle restarts.
Image by TheVisualMD
Lung and Bronchi of a Human Adult
Computer generated image reconstructed from scanned human data. This image presents a frontal view of the lungs of an adult. The average weight of left lung = 565 g, right lung = 625 g. The lungs are the primary organs in the respiratory system and are protected inside the rib cage. The bronchus and branch-like structures, bronchioles, highlighted in light blue, are depicted. Each bronchiole contains hundreds of alveoli, which are the sites of gas exchange. The red-brown, tube-like structure above the lungs is the trachea.
Image by TheVisualMD
Inhaling and exhaling | Respiratory system physiology | NCLEX-RN | Khan Academy
Video by khanacademymedicine/YouTube
Structure of Diaphragm shown using a 3D medical animation still shot
A 3D medical illustration showing structure of diaphragm and how it supports heart and lungs.
Image by Scientific Animations, Inc.
Thoracic diaphragm
Thoracic diaphragm - The diaphragm separates the thoracic and abdominal cavities.
Image by OpenStax College
Thoracic diaphragm
Respiratory system
Image by User Theresa knott
Thoracic diaphragm
Thoracic diaphragm - tachypnea
Image by Brbbl at nl.wikipedia
Muscles of the Diaphragm
The diaphragm separates the thoracic and abdominal cavities.
Image by CNX Openstax
Thorax with Muscle Involved in Respiration
3D visualization of an inferior view of the muscles involved in respiration. The primary job of the thorax is to promote movements necessary for breathing. Three muscles of the thorax assist in this function; the external intercostals, internal intercostals and diaphragm. The intercostals do the job of lifting the ribs up and pulling them outward, which in turn enlarges the lungs. As the lungs expand, the pressure inside them is reduced, and they suck in air. During extreme inhalation, the neck muscles also contract. During inhalation, the diaphragm contracts and pushes downward; during exhalation, it relaxes and is pushed up into a dome shape by the lower digestive organs, compressing the lungs. As pressure rises in the chest cavity, exhalation occurs, pressure is equalized and the cycle restarts.
Image by TheVisualMD
Human Lungs
Anatomy of the respiratory system, showing the trachea and both lungs and their lobes and airways. Lymph nodes and the diaphragm are also shown. Oxygen is inhaled into the lungs and passes through the thin membranes of the alveoli and into the bloodstream (see inset). (1) Note: The text and images above are in the public domain and were reproduced or adapted from the websites of the National Cancer Institute (NCI)
Image by National Cancer Institute
Thorax with Muscle Involved in Respiration
TheVisualMD
Lung and Bronchi of a Human Adult
TheVisualMD
12:59
Inhaling and exhaling | Respiratory system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
Structure of Diaphragm shown using a 3D medical animation still shot
Scientific Animations, Inc.
Thoracic diaphragm
OpenStax College
Thoracic diaphragm
User Theresa knott
Thoracic diaphragm
Brbbl at nl.wikipedia
Muscles of the Diaphragm
CNX Openstax
Thorax with Muscle Involved in Respiration
TheVisualMD
Human Lungs
National Cancer Institute
Respiratory Volumes and Capacities
Respiratory Health - Infant and Newborn Nutrition
Image by TheVisualMD
Respiratory Health - Infant and Newborn Nutrition
Respiratory Health : At birth, a baby makes a miraculous transition from getting oxygen via the placenta to breathing air through the lungs. A lipoprotein called surfactant is a critical part of healthy respiratory function. It enables tiny air sacs in the lungs, called alveoli, to remain open. This allows respiration. Surfactant also guards against pathogens and plays a role in immune function.
Image by TheVisualMD
Respiratory Volumes and Capacities
Under normal conditions, the average adult takes 12 to 15 breaths a minute. A breath is one complete respiratory cycle that consists of one inspiration and one expiration.
An instrument called a spirometer is used to measure the volume of air that moves into and out of the lungs, and the process of taking the measurements is called spirometry. Respiratory (pulmonary) volumes are an important aspect of pulmonary function testing because they can provide information about the physical condition of the lungs.
Respiratory capacity (pulmonary capacity) is the sum of two or more volumes.
Factors such as age, sex, body build, and physical conditioning have an influence on lung volumes and capacities. Lungs usually reach their maximumin capacity in early adulthood and decline with age after that.
Source: National Cancer Institute (NCI)
Additional Materials (17)
Man Swimming with Visible Skeleton and Lungs
This image features a man in a swimming pool wearing a swim cap and goggles. His skeleton and lungs are revealed. Our bodies are made of water more than any other single substance. About 60% of an adult's total body mass is water. The water within our bodies is sourced almost exclusively by the liquids we consume. Once ingested, water circulates in the bloodstream and is rationed to the body's tissues in an egalitarian system. Every organ requires water, whether directly or indirectly, though none receives more than the fair share needed for healthy development and functioning.
Image by TheVisualMD
Respiratory System of Male and Female
Medical visualization of the respiratory systems of a female and male. The translucent skin of both the male and female reveals the nasal cavity, trachea and the lungs.
Image by TheVisualMD
Sensitive content
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Female Thorax with Visible Lung
3D visualization of an anterior oblique view of the lungs and trachea reconstructed from scanned human data. Muscular and compact, the respiratory system consists of branching tubes that perform two functions - one concerned with getting enormous volumes of air in and out of the body; and the other concentrated on getting oxygen into, and carbon dioxide out of the blood.
Image by TheVisualMD
Respiratory Health
An extraordinary sequence of events must take place before a baby can cry out for the first time. Infant development researchers refer to the moments that surround this milestone as the "transition to extrauterine life." Indeed. The baby is delivered, still attached by its lifeline, the umbilical cord, to the remarkable but temporary organ, the placenta, that has sustained the fetus and met all of its physiological needs. Within seconds after this connection has been abruptly broken, the baby must breathe on her own for the first time so that her circulatory system can deliver oxygen to all of the tissues throughout her body. Though this dramatic shift seems nothing short of miraculous, the great majority of babies leap across this transition with nothing more than a loud cry of recognition.
Image by TheVisualMD
Male Thorax with Visible Trachea and Lung
3D visualization of an anterior oblique view of the lungs and trachea reconstructed from scanned human data. Muscular and compact, the respiratory system consists of branching tubes that perform two functions - one concerned with getting enormous volumes of air in and out of the body; and the other concentrated on getting oxygen into, and carbon dioxide out of the blood.
Air enters the respiratory system through the nasal cavity and pharynx, and then passes through the trachea and into the bronchi, which bring air into the lungs. (credit: modification of work by NCI)
Image by CNX Openstax (credit: modification of work by NCI)
Pulmonary circulation
Diagram of pulmonary circulation. Oxygen-rich blood is shown in red; oxygen-depleted blood in blue.
Image by OpenStax College
Human Lungs
Anatomy of the respiratory system, showing the trachea and both lungs and their lobes and airways. Lymph nodes and the diaphragm are also shown. Oxygen is inhaled into the lungs and passes through the thin membranes of the alveoli and into the bloodstream (see inset). (1) Note: The text and images above are in the public domain and were reproduced or adapted from the websites of the National Cancer Institute (NCI)
Image by National Cancer Institute
This browser does not support the video element.
Heart and Pulmonary System
An animation of a close up of the heart and pulmonary system. The camera rotates from right to left to show the heart, bronchi, pulmonary arteries, veins, within glass lungs, and a semi-transparent thorax and scapula. Since this animation was created in VG-Studiomax the background is black
Video by TheVisualMD
Human Lungs
Illustration of bronchi and lungs
Image by US GOV
Inspiration and Expiration
Inspiration and Expiration
Image by OpenStax College
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This media may include sensitive content
Lungs
Lung expansion gif simulation using raccoon lungs and an air compressor.
Image by Meddlingwithnature
Human lungs
Basic anatomy of a human lung
Image by Sumaiya
Human lungs
Gross Anatomy of the Lungs
Image by OpenStax College
Human lungs
Artificially colored 3D rendering of a high resolution computed tomography of a normal thorax of a 37 year old man who presented with unspecific breathing problems, published with written informed consent. The anterior thoracic wall, the airways and the pulmonary vessels anterior to the root of the lung have been digitally removed in order to visualize the different levels of the pulmonary circulation.
Image by Mikael Haggstrom
Human respiratory system
Diagram of the human respiratory system
Image by United States National Institute of Health: National Heart, Lung and Blood Institute
CNX Openstax (credit: modification of work by NCI)
Pulmonary circulation
OpenStax College
Human Lungs
National Cancer Institute
0:10
Heart and Pulmonary System
TheVisualMD
Human Lungs
US GOV
Inspiration and Expiration
OpenStax College
Sensitive content
This media may include sensitive content
Lungs
Meddlingwithnature
Human lungs
Sumaiya
Human lungs
OpenStax College
Human lungs
Mikael Haggstrom
Human respiratory system
United States National Institute of Health: National Heart, Lung and Blood Institute
Conducting Zone- Nose, Pharynx, Larynx, Trachea, Bronchial Tree
3D Medical Animation Still Shot Depicting Nose
Image by Scientific Animations, Inc.
3D Medical Animation Still Shot Depicting Nose
3D Medical Animation Still Shot Depicting Nose & its Basic Internal Structure.
Image by Scientific Animations, Inc.
Conducting Zone- Nose, Pharynx, Larynx, Trachea, Bronchial Tree
Conducting Zone
The major functions of the conducting zone are to provide a route for incoming and outgoing air, remove debris and pathogens from the incoming air, and warm and humidify the incoming air. Several structures within the conducting zone perform other functions as well. The epithelium of the nasal passages, for example, is essential to sensing odors, and the bronchial epithelium that lines the lungs can metabolize some airborne carcinogens.
The Nose and its Adjacent Structures
The major entrance and exit for the respiratory system is through the nose. When discussing the nose, it is helpful to divide it into two major sections: the external nose, and the nasal cavity or internal nose.
The external nose consists of the surface and skeletal structures that result in the outward appearance of the nose and contribute to its numerous functions (image). The root is the region of the nose located between the eyebrows. The bridge is the part of the nose that connects the root to the rest of the nose. The dorsum nasi is the length of the nose. The apex is the tip of the nose. On either side of the apex, the nostrils are formed by the alae (singular = ala). An ala is a cartilaginous structure that forms the lateral side of each naris (plural = nares), or nostril opening. The philtrum is the concave surface that connects the apex of the nose to the upper lip.
Nose
This illustration shows features of the external nose (top) and skeletal features of the nose (bottom).
Underneath the thin skin of the nose are its skeletal features (see image, lower illustration). While the root and bridge of the nose consist of bone, the protruding portion of the nose is composed of cartilage. As a result, when looking at a skull, the nose is missing. The nasal bone is one of a pair of bones that lies under the root and bridge of the nose. The nasal bone articulates superiorly with the frontal bone and laterally with the maxillary bones. Septal cartilage is flexible hyaline cartilage connected to the nasal bone, forming the dorsum nasi. The alar cartilage consists of the apex of the nose; it surrounds the naris.
The nares open into the nasal cavity, which is separated into left and right sections by the nasal septum (image). The nasal septum is formed anteriorly by a portion of the septal cartilage (the flexible portion you can touch with your fingers) and posteriorly by the perpendicular plate of the ethmoid bone (a cranial bone located just posterior to the nasal bones) and the thin vomer bones (whose name refers to its plough shape). Each lateral wall of the nasal cavity has three bony projections, called the superior, middle, and inferior nasal conchae. The inferior conchae are separate bones, whereas the superior and middle conchae are portions of the ethmoid bone. Conchae serve to increase the surface area of the nasal cavity and to disrupt the flow of air as it enters the nose, causing air to bounce along the epithelium, where it is cleaned and warmed. The conchae and meatuses also conserve water and prevent dehydration of the nasal epithelium by trapping water during exhalation. The floor of the nasal cavity is composed of the palate. The hard palate at the anterior region of the nasal cavity is composed of bone. The soft palate at the posterior portion of the nasal cavity consists of muscle tissue. Air exits the nasal cavities via the internal nares and moves into the pharynx.
Upper Airway
Several bones that help form the walls of the nasal cavity have air-containing spaces called the paranasal sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each paranasal sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses produce mucus and lighten the weight of the skull.
The nares and anterior portion of the nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to prevent the passage of large debris, such as dirt, through the nasal cavity. An olfactory epithelium used to detect odors is found deeper in the nasal cavity.
The conchae, meatuses, and paranasal sinuses are lined by respiratory epithelium composed of pseudostratified ciliated columnar epithelium (image). The epithelium contains goblet cells, one of the specialized, columnar epithelial cells that produce mucus to trap debris. The cilia of the respiratory epithelium help remove the mucus and debris from the nasal cavity with a constant beating motion, sweeping materials towards the throat to be swallowed. Interestingly, cold air slows the movement of the cilia, resulting in accumulation of mucus that may in turn lead to a runny nose during cold weather. This moist epithelium functions to warm and humidify incoming air. Capillaries located just beneath the nasal epithelium warm the air by convection. Serous and mucus-producing cells also secrete the lysozyme enzyme and proteins called defensins, which have antibacterial properties. Immune cells that patrol the connective tissue deep to the respiratory epithelium provide additional protection.
The pharynx is a tube formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities (see image). The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx (image).
Divisions of the Pharynx
The pharynx is divided into three regions: the nasopharynx, the oropharynx, and the laryngopharynx.
The nasopharynx is flanked by the conchae of the nasal cavity, and it serves only as an airway. At the top of the nasopharynx are the pharyngeal tonsils. A pharyngeal tonsil, also called an adenoid, is an aggregate of lymphoid reticular tissue similar to a lymph node that lies at the superior portion of the nasopharynx. The function of the pharyngeal tonsil is not well understood, but it contains a rich supply of lymphocytes and is covered with ciliated epithelium that traps and destroys invading pathogens that enter during inhalation. The pharyngeal tonsils are large in children, but interestingly, tend to regress with age and may even disappear. The uvula is a small bulbous, teardrop-shaped structure located at the apex of the soft palate. Both the uvula and soft palate move like a pendulum during swallowing, swinging upward to close off the nasopharynx to prevent ingested materials from entering the nasal cavity. In addition, auditory (Eustachian) tubes that connect to each middle ear cavity open into the nasopharynx. This connection is why colds often lead to ear infections.
The oropharynx is a passageway for both air and food. The oropharynx is bordered superiorly by the nasopharynx and anteriorly by the oral cavity. The fauces is the opening at the connection between the oral cavity and the oropharynx. As the nasopharynx becomes the oropharynx, the epithelium changes from pseudostratified ciliated columnar epithelium to stratified squamous epithelium. The oropharynx contains two distinct sets of tonsils, the palatine and lingual tonsils. A palatine tonsil is one of a pair of structures located laterally in the oropharynx in the area of the fauces. The lingual tonsil is located at the base of the tongue. Similar to the pharyngeal tonsil, the palatine and lingual tonsils are composed of lymphoid tissue, and trap and destroy pathogens entering the body through the oral or nasal cavities.
The laryngopharynx is inferior to the oropharynx and posterior to the larynx. It continues the route for ingested material and air until its inferior end, where the digestive and respiratory systems diverge. The stratified squamous epithelium of the oropharynx is continuous with the laryngopharynx. Anteriorly, the laryngopharynx opens into the larynx, whereas posteriorly, it enters the esophagus.
Larynx
The larynx is a cartilaginous structure inferior to the laryngopharynx that connects the pharynx to the trachea and helps regulate the volume of air that enters and leaves the lungs (image). The structure of the larynx is formed by several pieces of cartilage. Three large cartilage pieces—the thyroid cartilage (anterior), epiglottis (superior), and cricoid cartilage (inferior)—form the major structure of the larynx. The thyroid cartilage is the largest piece of cartilage that makes up the larynx. The thyroid cartilage consists of the laryngeal prominence, or “Adam’s apple,” which tends to be more prominent in males. The thick cricoid cartilage forms a ring, with a wide posterior region and a thinner anterior region. Three smaller, paired cartilages—the arytenoids, corniculates, and cuneiforms—attach to the epiglottis and the vocal cords and muscle that help move the vocal cords to produce speech.
Larynx
The larynx extends from the laryngopharynx and the hyoid bone to the trachea.
The epiglottis, attached to the thyroid cartilage, is a very flexible piece of elastic cartilage that covers the opening of the trachea (see image). When in the “closed” position, the unattached end of the epiglottis rests on the glottis. The glottis is composed of the vestibular folds, the true vocal cords, and the space between these folds (image). A vestibular fold, or false vocal cord, is one of a pair of folded sections of mucous membrane. A true vocal cord is one of the white, membranous folds attached by muscle to the thyroid and arytenoid cartilages of the larynx on their outer edges. The inner edges of the true vocal cords are free, allowing oscillation to produce sound. The size of the membranous folds of the true vocal cords differs between individuals, producing voices with different pitch ranges. Folds in males tend to be larger than those in females, which create a deeper voice. The act of swallowing causes the pharynx and larynx to lift upward, allowing the pharynx to expand and the epiglottis of the larynx to swing downward, closing the opening to the trachea. These movements produce a larger area for food to pass through, while preventing food and beverages from entering the trachea.
Vocal Cords
The true vocal cords and vestibular folds of the larynx are viewed inferiorly from the laryngopharynx.
Continuous with the laryngopharynx, the superior portion of the larynx is lined with stratified squamous epithelium, transitioning into pseudostratified ciliated columnar epithelium that contains goblet cells. Similar to the nasal cavity and nasopharynx, this specialized epithelium produces mucus to trap debris and pathogens as they enter the trachea. The cilia beat the mucus upward towards the laryngopharynx, where it can be swallowed down the esophagus.
Trachea
The trachea (windpipe) extends from the larynx toward the lungs (imagea). The trachea is formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage that are connected by dense connective tissue. The trachealis muscle and elastic connective tissue together form the fibroelastic membrane, a flexible membrane that closes the posterior surface of the trachea, connecting the C-shaped cartilages. The fibroelastic membrane allows the trachea to stretch and expand slightly during inhalation and exhalation, whereas the rings of cartilage provide structural support and prevent the trachea from collapsing. In addition, the trachealis muscle can be contracted to force air through the trachea during exhalation. The trachea is lined with pseudostratified ciliated columnar epithelium, which is continuous with the larynx. The esophagus borders the trachea posteriorly.
The trachea branches into the right and left primary bronchi at the carina. These bronchi are also lined by pseudostratified ciliated columnar epithelium containing mucus-producing goblet cells (imageb). The carina is a raised structure that contains specialized nervous tissue that induces violent coughing if a foreign body, such as food, is present. Rings of cartilage, similar to those of the trachea, support the structure of the bronchi and prevent their collapse. The primary bronchi enter the lungs at the hilum, a concave region where blood vessels, lymphatic vessels, and nerves also enter the lungs. The bronchi continue to branch into bronchial a tree. A bronchial tree (or respiratory tree) is the collective term used for these multiple-branched bronchi. The main function of the bronchi, like other conducting zone structures, is to provide a passageway for air to move into and out of each lung. In addition, the mucous membrane traps debris and pathogens.
A bronchiole branches from the tertiary bronchi. Bronchioles, which are about 1 mm in diameter, further branch until they become the tiny terminal bronchioles, which lead to the structures of gas exchange. There are more than 1000 terminal bronchioles in each lung. The muscular walls of the bronchioles do not contain cartilage like those of the bronchi. This muscular wall can change the size of the tubing to increase or decrease airflow through the tube.
Source: CNX OpenStax
Additional Materials (50)
Glass Lungs with visible Smoke Inhalation
A view of glass lungs in a male smoker's body, with the bronchial tree visible. Part of an interactive depictions of the pathway of nicotine, this image shows the trachea, bronchus, and branching bronchioles that will terminate in alveoli, as well as the ribcage and intracostal muscles.
Image by TheVisualMD
Larynx, Trachea, Bronchi, and Lungs
Trachea and Lungs : Visualization of the human respiratory tract and heart, based on segmented human data. The thyroid cartilage resides above the trachea. The trachea branches above the heart into the two lungs. Several branching bronchi and bronchioles are shown penetrating throughout the lungs. The bronchiole tree conducts air, allowing oxygen to pass into the lungs and carbon monoxide to exit.
Image by TheVisualMD
Thorax with Visible Lung and Bronchial Tree
3D visualization of an anterioinferior view of the thorax reconstructed from scanned human data. When air is inhaled into the lungs, it flows through large tubes called bronchi, branches into smaller tubes known as bronchioles, and ends up in the thousands of small pouches that are the alveoli. This is where the oxygen is transferred from the air into the bloodstream. Each alveolar sac, or air sac, is surrounded by a bed of capillaries, and the walls between the lung and the capillary are extremely thin. The walls are so delicate, in fact, that the inhaled oxygen can seep from the air sacs to bind to the hemoglobin in the blood, while the carbon dioxide and other waste gasses leave the blood and diffuse into the lungs where they can be exhaled.
Image by TheVisualMD
Pharynx and Upper Digestive Tract
Pharynx and Upper Digestive Tract : 3D visualization reconstructed from scanned human data of an anteriolateral view of torso revealing the upper digestive tract. The upper digestive system is primarily concerned with the ingestion and propulsion of food and is composed of the oral cavity, teeth, tongue, salivary glands, pharynx, and esophagus. Mechanical and chemical digestion begin in the mouth with the process of mastication and the action of saliva. The voluntary and involuntary process of swallowing pushes the food through the pharynx to the esophagus, where it moves to the stomach by way of peristalsis.
Image by TheVisualMD
Obese Head with Pharynx cross section
The pharynx is the part of the gastrointestinal and respiratory tracts that lies between the mouth and the esophagus. It extends through the oral and nasal cavities to the trachea and esophagus. In the pharynx wall are found pairs of muscles that join at the center back and encircle the pharynx to reach various attachments in front. These include the hyoid bone at the base of the tongue and the cartilage of the Adam's apple. Obstructive sleep apnea (OSA), the temporary stoppage of breathing during sleep, is due to airflow obstruction caused by collapse of the pharynx. About 70% of people with OSA are obese-that is, they have a body mass index (BMI) of 30 or greater. Roughly 40% of obese men and women have OSA. Every 22-lb increase in body weight doubles your risk of OSA. Carrying excess fat in the abdomen and upper body rather than on the hips increases the likelihood of OSA. Obesity contributes to sleep apnea in a number of ways. Fat cells start to infiltrate the tissues of the neck and throat, causing them to enlarge and lose tone. Visceral fat, abdominal fat that fills up the space around the internal organs, crowds the organs and presses up on the diaphragm. When the diaphragm is pressed in this way, it's harder for it to move down and allow the lungs to fill with air. Lying down or leaning back causes the weight of the excess fat to press down on the chest and abdomen. It may be difficult, or even impossible, to take deep breaths and fill the lungs with air.
Image by TheVisualMD
Respiratory Tree Anatomy - Conducting Zone & Respiratory Zone
Video by USMLEFastTrack/YouTube
Pharynx
Divisions of the Pharynx
Image by OpenStax College
Upper Airway
Image by CNX Openstax
Divisions of the Pharynx
The pharynx is divided into three regions: the nasopharynx, the oropharynx, and the laryngopharynx.
Image by CNX Openstax
Pharynx
The pharynx runs from the nostrils to the esophagus and the larynx.
Image by CNX Openstax
Pharynx
Anatomy of Nose-Pharynx-Mouth-Larynx
Image by OpenStax College
Pharynx
Divisions of the Pharynx
Image by OpenStax College
Nasal septum
A CT image showing a congenitally deviated nasal septum
Image by OpenStax College
Diagram showing the parts of the pharynx
Diagram showing the parts of the pharynx
Image by Cancer Research UK / Wikimedia Commons
Head with Pharynx and nose cross section
Head with Pharynx and nose cross section
Image by TheVisualMD
Systems of Gas Exchange
Air enters the respiratory system through the nasal cavity and pharynx, and then passes through the trachea and into the bronchi, which bring air into the lungs. (credit: modification of work by NCI)
Image by CNX Openstax (credit: modification of work by NCI)
Anatomy of Upper Digestive Tract Involved in Swallowing
3D visualization reconstructed from scanned human data of anatomical structures of the head involved in digestive functions. Saliva produced in the three salivary glands (sublingual, submandibular, and parotid) is delivered to the oral cavity via salivary ducts. Saliva serves mutiple functions: lubricating and cleansing the mouth, dissolving food so that it can be detected by tate buds, and secreting enzymes that begin the chemical breakdown of starches. Swallowing, or deglutition, is a complicated process involving over 22 muscle groups and the coordination of the tongue, soft palate, pharynx, and esophagus. The first stage is voluntary, when the tongue is pressed against the roof of the mouth and is contracted to pass the food to the oropharynx. The second stage ,which is involuntary, involves the uplifting of the larynx to allow the epiglottis to cover the trachea while peristaltic contractions moves food down the pharynx and esophagus.
Image by TheVisualMD
Nasopharynx
Pharynx overview
Image by Semhur
Pharynx
Head and neck anatomy
Image by US GOV
Diagram of the larynx
Diagram of the larynx
Image by Cancer Research UK / Wikimedia Commons
Diagram showing the position of the larynx
Diagram showing the position of the larynx.
Image by Cancer Research UK / Wikimedia Commons
Larynx and Upper Respiratory Tract
Larynx and Upper Respiratory Tract
Image by TheVisualMD
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LARYNX & TRACHEA anatomy
Normal Larynx, Larynx. 1=vocal chords, 2=vestibular fold, 3=epiglottis, 4=aryepiglottic folds, 5=arytenoid cartilage, 6=sinus piriformis, 7=base of the tongue
Image by Welleschik
Larynx from a case of croup
Watercolour drawing of a larynx from a case of croup, in which the exudation does not extend below the glottis.
Medical Photographic Library
Keywords: Godart, Thomas
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LARYNX & TRACHEA anatomy
Larynx
Image by Welleschik
LARYNX & TRACHEA anatomy
Illustration of Larynx
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LARYNX & TRACHEA anatomy
Larynx
Image by Welleschik
posterior and anterior view of the anatomy of the larynx
A 3D medical illustration of the posterior and anterior view of the anatomy of the larynx.
Image by the University of Dundee and BodyParts3D - by Annie Campbell
Larynx
The larynx extends from the laryngopharynx and the hyoid bone to the trachea.
Image by CNX Openstax
Larynx (top view)
Larynx (Top View) - Description A top view of the larynx (seen with a mirror). The epiglottis, vocal cords, trachea, and cartilage are labeled.
Image by Alan Hoofring (Illustrator) / National Cancer Institute
LARYNX & TRACHEA anatomy
Larynx and Nearby Structures
Image by National Cancer Institute, Alan Hoofring (Illustrator)
LARYNX & TRACHEA anatomy
Larynx and Nearby Structures
Image by US GOV
LARYNX & TRACHEA anatomy
Illustration of Larynx
Image by Vbsystem
LARYNX
Diagram of the larynx.
Image by Cancer Research UK / Wikimedia Commons
LARYNX
Diagram showing the position of the larynx.
Image by Cancer Research UK / Wikimedia Commons
Cartilage Anatomy of the Larynx
Cartilage Anatomy of the Larynx - 3D medical illustration of the posterior view of the larynx showing the anatomy of the cartilaginous structures within that area.
Image by the University of Dundee and BodyParts3D - by Annie Campbell
Vocal Cords
The true vocal cords and vestibular folds of the larynx are viewed inferiorly from the laryngopharynx.
Image by CNX Openstax
Cartilages of the Larynx
Cartilages of the Larynx
Image by OpenStax College
Trachea, Bronchi, Larynx
Trachea, Bronchi, Larynx
Image by CNX OpenStax
Trachea, Bronchi, Larynx
Trachea, Bronchi, Larynx
Image by Madhero88
Trachea, Bronchi, Larynx
Trachea, Bronchi, Larynx
Image by OpenStax Anatomy and Physiology
Trachea, Bronchi, Larynx
Trachea, Bronchi, Larynx
Image by DataBase Center for Life Science (DBCLS)
Supraglottis
Image by US Gov
Vocal Cords LARYNX & TRACHEA anatomy
Vocal folds. When the intrinsic muscles of the larynx contract, they pull on the arytenoid cartilages, which causes them to pivot. Contraction of the posterior cricoarytenoid muscle, for example, moves the vocal folds apart (abduction), thereby opening the rima glottidis. By contrast, contraction of the lateralcricoarytenoid muscle moves the vocal folds together (adduction), therby closing the rima glottidis.
The main parts of the larynx (supraglottis, glottis, and subglottis) and other nearby structures, including the nasal cavity, mouth, cartilage, vocal cords, trachea and esophagus.
Image by National Cancer Institute / Alan Hoofring (Illustrator)
Systems of Gas Exchange
The trachea and bronchi are made of incomplete rings of cartilage. (credit: modification of work by Gray's Anatomy)
Image by CNX Openstax (credit: modification of work by Gray's Anatomy)
Bronchi Transport Air in the Respiratory System
Respiration is how the body absorbs oxygen from the air and eliminates the carbon dioxide produced by the body's cells. The respiratory system is chiefly composed of the nasal and oral cavities, larynx, pharynx, trachea, and lungs, along with the smaller bronchi and microscopic air sacs called alveoli within the lungs. Fetal lung tissue matures late in gestation and is filled with amniotic fluid until birth. A protein-lipid combination called surfactant plays a critical role in lung development. Surfactant maintains proper surface tension in the alveoli, keeping them from collapsing and making breathing possible. Researchers have discovered that nutrients such as vitamin D also play important roles in the healthy development of the infant's respiratory system.
Image by TheVisualMD
Bronchial tree is a system of airways in which the "trunk" is the windpipe and the "branches" are the subdividing passages that permeate the lungs.
3D visualization of an anterior view of the respiratory system of an adult male, reconstructed from scanned human data. The upper respiratory system, including coronal sections of the paranasal sinuses and the oral cavity, are visible through areas of transparent skin on the face. The respiratory system consists of branching tubes that work to bring oxygen from the air to the organs and tissues of the body, and to expel carbon dioxide wastes from the body to the air. The bronchial tree is a system of airways in which the "trunk" is the windpipe and the "branches" are the subdividing passages that permeate the lungs. While the rest of the system works as a kind of accordion pump, the structures of the bronchial network split and split again until they are so numerous and so thin at their membranous tips that gas molecules can cross over to the blood through a network of capillaries that, laid end to end, would measure more than 1,000 miles.
Image by TheVisualMD
BREATHING LESSON
We take approximately 20,000 breaths each day. When the air we take in through the nose and mouth reaches the trachea, it travels a path of ever-smaller tubes: the bronchial tree. Bronchioles, the smallest tubes in the bronchial tree, end in clusters of tiny air sacs called alveoli. A tight, delicate web of capillaries surrounds the alveolar sacs. Inside each capillary, oxygen molecules bind to red blood cells. Every cell in the body needs oxygen, and red blood cells deliver it. Then, they take carbon dioxide and other waste back toward the lungs to be exhaled. A security system protects this vital process. Sticky mucus coats the airways, and traps microbes and pollution. Then hairlike cilia, which line the airways, make a wavelike motion to push mucus back toward the mouth and nose to be expelled.
Image by TheVisualMD
Glass Lungs with visible Smoke Inhalation
TheVisualMD
Larynx, Trachea, Bronchi, and Lungs
TheVisualMD
Thorax with Visible Lung and Bronchial Tree
TheVisualMD
Pharynx and Upper Digestive Tract
TheVisualMD
Obese Head with Pharynx cross section
TheVisualMD
2:06
Respiratory Tree Anatomy - Conducting Zone & Respiratory Zone
USMLEFastTrack/YouTube
Pharynx
OpenStax College
Upper Airway
CNX Openstax
Divisions of the Pharynx
CNX Openstax
Pharynx
CNX Openstax
Pharynx
OpenStax College
Pharynx
OpenStax College
Nasal septum
OpenStax College
Diagram showing the parts of the pharynx
Cancer Research UK / Wikimedia Commons
Head with Pharynx and nose cross section
TheVisualMD
Systems of Gas Exchange
CNX Openstax (credit: modification of work by NCI)
Anatomy of Upper Digestive Tract Involved in Swallowing
TheVisualMD
Nasopharynx
Semhur
Pharynx
US GOV
Diagram of the larynx
Cancer Research UK / Wikimedia Commons
Diagram showing the position of the larynx
Cancer Research UK / Wikimedia Commons
Larynx and Upper Respiratory Tract
TheVisualMD
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LARYNX & TRACHEA anatomy
Welleschik
Larynx from a case of croup
/Wikimedia
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LARYNX & TRACHEA anatomy
Welleschik
LARYNX & TRACHEA anatomy
OpenStax College
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LARYNX & TRACHEA anatomy
Welleschik
posterior and anterior view of the anatomy of the larynx
the University of Dundee and BodyParts3D - by Annie Campbell
Larynx
CNX Openstax
Larynx (top view)
Alan Hoofring (Illustrator) / National Cancer Institute
LARYNX & TRACHEA anatomy
National Cancer Institute, Alan Hoofring (Illustrator)
LARYNX & TRACHEA anatomy
US GOV
LARYNX & TRACHEA anatomy
Vbsystem
LARYNX
Cancer Research UK / Wikimedia Commons
LARYNX
Cancer Research UK / Wikimedia Commons
Cartilage Anatomy of the Larynx
the University of Dundee and BodyParts3D - by Annie Campbell
Vocal Cords
CNX Openstax
Cartilages of the Larynx
OpenStax College
Trachea, Bronchi, Larynx
CNX OpenStax
Trachea, Bronchi, Larynx
Madhero88
Trachea, Bronchi, Larynx
OpenStax Anatomy and Physiology
Trachea, Bronchi, Larynx
DataBase Center for Life Science (DBCLS)
Supraglottis
US Gov
Vocal Cords LARYNX & TRACHEA anatomy
US GOV
Thyroid Gland
CNX Openstax
Larynx and Nearby Structures
National Cancer Institute / Alan Hoofring (Illustrator)
Systems of Gas Exchange
CNX Openstax (credit: modification of work by Gray's Anatomy)
Bronchi Transport Air in the Respiratory System
TheVisualMD
Bronchial tree is a system of airways in which the "trunk" is the windpipe and the "branches" are the subdividing passages that permeate the lungs.
TheVisualMD
BREATHING LESSON
TheVisualMD
Respiratory Zone - Alveoli
Respiratory System - Alveolus and Surrounding Capillary of Lung
Image by TheVisualMD
Respiratory System - Alveolus and Surrounding Capillary of Lung
3D visualization reconstructed from scanned human data of the heart and airways of the lungs. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery and veins are the only vessels that break the rules about arteries carrying oxygenated blood and veins carrying deoxygenated blood. Technically arteries carry blood away from the heart, and veins carry it back. Everywhere else in the body, blood flowing away from the heart is oxygenated, and blood flowing back to the heart is deoxygenated, but not in the lungs. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
Respiratory Zone - Alveoli
Respiratory Zone
In contrast to the conducting zone, the respiratory zone includes structures that are directly involved in gas exchange. The respiratory zone begins where the terminal bronchioles join a respiratory bronchiole, the smallest type of bronchiole (image), which then leads to an alveolar duct, opening into a cluster of alveoli.
Respiratory Zone
Bronchioles lead to alveolar sacs in the respiratory zone, where gas exchange occurs.
Alveoli
An alveolar duct is a tube composed of smooth muscle and connective tissue, which opens into a cluster of alveoli. An alveolus is one of the many small, grape-like sacs that are attached to the alveolar ducts.
An alveolar sac is a cluster of many individual alveoli that are responsible for gas exchange. An alveolus is approximately 200 μm in diameter with elastic walls that allow the alveolus to stretch during air intake, which greatly increases the surface area available for gas exchange. Alveoli are connected to their neighbors by alveolar pores, which help maintain equal air pressure throughout the alveoli and lung (image).
The alveolar wall consists of three major cell types: type I alveolar cells, type II alveolar cells, and alveolar macrophages. A type I alveolar cell is a squamous epithelial cell of the alveoli, which constitute up to 97 percent of the alveolar surface area. These cells are about 25 nm thick and are highly permeable to gases. A type II alveolar cell is interspersed among the type I cells and secretes pulmonary surfactant, a substance composed of phospholipids and proteins that reduces the surface tension of the alveoli. Roaming around the alveolar wall is the alveolar macrophage, a phagocytic cell of the immune system that removes debris and pathogens that have reached the alveoli.
The simple squamous epithelium formed by type I alveolar cells is attached to a thin, elastic basement membrane. This epithelium is extremely thin and borders the endothelial membrane of capillaries. Taken together, the alveoli and capillary membranes form a respiratory membrane that is approximately 0.5 mm thick. The respiratory membrane allows gases to cross by simple diffusion, allowing oxygen to be picked up by the blood for transport and CO2 to be released into the air of the alveoli.
Diseases of the…
Respiratory System: Asthma Asthma is common condition that affects the lungs in both adults and children. Approximately 8.2 percent of adults (18.7 million) and 9.4 percent of children (7 million) in the United States suffer from asthma. In addition, asthma is the most frequent cause of hospitalization in children.
Asthma is a chronic disease characterized by inflammation and edema of the airway, and bronchospasms (that is, constriction of the bronchioles), which can inhibit air from entering the lungs. In addition, excessive mucus secretion can occur, which further contributes to airway occlusion (image). Cells of the immune system, such as eosinophils and mononuclear cells, may also be involved in infiltrating the walls of the bronchi and bronchioles.
Bronchospasms occur periodically and lead to an “asthma attack.” An attack may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress.
Normal and Bronchial Asthma Tissues
(a) Normal lung tissue does not have the characteristics of lung tissue during (b) an asthma attack, which include thickened mucosa, increased mucus-producing goblet cells, and eosinophil infiltrates.
Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of the chest. Symptoms of a severe asthma attack that requires immediate medical attention would include difficulty breathing that results in blue (cyanotic) lips or face, confusion, drowsiness, a rapid pulse, sweating, and severe anxiety. The severity of the condition, frequency of attacks, and identified triggers influence the type of medication that an individual may require. Longer-term treatments are used for those with more severe asthma. Short-term, fast-acting drugs that are used to treat an asthma attack are typically administered via an inhaler. For young children or individuals who have difficulty using an inhaler, asthma medications can be administered via a nebulizer.
In many cases, the underlying cause of the condition is unknown. However, recent research has demonstrated that certain viruses, such as human rhinovirus C (HRVC), and the bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae that are contracted in infancy or early childhood, may contribute to the development of many cases of asthma.
Source: CNX OpenStax
Additional Materials (23)
Carbon Dioxide exchange in the Alveoli
Carbon Dioxide exchange in the Alveoli - Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. (NCBI/NLM/NIH)
Image by TheVisualMD
Overview of the Respiratory System, Animation
Video by Alila Medical Media/YouTube
Alveoli of Lung
When you breathe, oxygenated air flows through your lungs and ends up in thousands of small air sacs in the lungs called alveoli. The right side of your heart sends deoxygenated blood to the capillaries surrounding these alveoli. The walls between the alveoli and the capillaries are extremely thin, so that the inhaled oxygen can seep from the air sacs to bind to the hemoglobin molecules in the erythrocytes. Carbon dioxide and other waste gases leave the blood and diffuse into the air sacs, where they are exhaled through the lungs. This gas exchange is passive: oxygen goes from the higher concentration in the lungs to the lower concentration in the blood. Similarly, carbon dioxide goes from the blood to the lungs.
Image by TheVisualMD
Your lung is a living breathing miracle
Your lungs are the only internal organs of your body that are constantly exposed to the outside world-that is, the air you breathe. Air contains oxygen, the vital gas that fuels all your metabolic processes. But air can also contain pollutants, irritants, and allergens. When you inhale, air passes down the back of your throat, past your vocal cords, and into your windpipe, or trachea. Your trachea divides into twin air pipes (one for each lung) called the bronchi. Much the way in which a tree branches, the bronchi continue to divide into smaller air passages called bronchioles. Collectively, these air passages are known as the airways. The bronchioles continue to branch until they become extremely narrow—the small airways are less than 2 micrometers in diameter! They end in microscopic air sacs called alveoli. Your lungs contain about 500 million alveoli. Alveoli have very thin walls and are surrounded by a dense network of tiny capillaries. When you breathe, the oxygen-filled air you inhale goes down into your lungs and deep into the alveoli. Carbon dioxide that has been released from your body’s cells as a waste product—a by-product of cellular respiration—is carried by your bloodstream until it reaches the capillaries of the alveoli. Normally we breathe through our noses, not our mouths, to prepare air for the lower respiratory tract. When you inhale through your nose, the air is moistened and heated. Nasal hairs partially filter out particles in the air. Your nasal passages contain smaller hairs, called cilia, that also help to filter out foreign matter. Cilia are found along your air passages as well. Cilia move in a sweeping motion to help keep your airways free of particles and pollutants. Smoking paralyzes your cilia and stops them from functioning properly. That’s one reason smokers often get respiratory ailments, like bronchitis. The levels of oxygen and carbon dioxide in your blood must remain balanced and constant. That means the huge volume of air you breathe—from 2,100 to 2,400 gal (8,000- 9,000 L) of air each day—needs to flow freely and constantly into and out of your lungs. For air to flow freely, your airways must remain open and unconstricted by their muscular walls. They also must produce just the right amount of mucus: enough to wet the interior of the tubes, but not enough to impede the passage of air.
Image by TheVisualMD
Systems of Gas Exchange
Terminal bronchioles are connected by respiratory bronchioles to alveolar ducts and alveolar sacs. Each alveolar sac contains 20 to 30 spherical alveoli and has the appearance of a bunch of grapes. Air flows into the atrium of the alveolar sac, then circulates into alveoli where gas exchange occurs with the capillaries. Mucous glands secrete mucous into the airways, keeping them moist and flexible. (credit: modification of work by Mariana Ruiz Villareal)
Image by CNX Openstax (credit: modification of work by Mariana Ruiz Villareal)
Heart pulmonary and great vessels
Heart pulmonary and great vessels
Image by TheVisualMD
Fluid-Filled Alveoli Within the Lungs
Fluid-Filled Alveoli Within the Lungs
Image by TheVisualMD
Fluid-Filled Alveoli Within the Lungs
In pulmonary edema, also known as congestive heart failure, fluid fills the alveoli (air sacs) of the lungs. This can occur when a ventricular arrhythmia causes the left ventricle to be unable to pump out enough of the blood it receives from the lungs, or when the right ventricle can't overcome increased pressure in the pulmonary artery due to left heart failure.
Image by TheVisualMD
Lung with Visible Bronchi and Bronchiole
The pulmonary circulation and systemic circulation are tied together - in that they work in synchrony to provide the body with oxygen and to get rid of the body's carbon dioxide. Enzymes digest, or break down, the carbohydrates from the foods you eat into sugars, which the cells of your body use to produce energy. Oxygen is needed for energy production and carbon dioxide is one of the waste products. These gases are transported by your cardiovascular system through the blood. Your blood has cells called red blood cells, or erythrocytes. These cells have molecules (hemoglobin), which can bind to or release oxygen as needed. When you breathe, oxygenated air flows through your lungs and ends up in thousands of small air sacs in the lungs called alveoli. The right side of your heart sends deoxygenated blood to the capillaries surrounding these alveoli. The walls between the alveoli and the capillaries are extremely thin, so that the inhaled oxygen can seep from the air sacs to bind to the hemoglobin molecules in the erythrocytes. Carbon dioxide and other waste gases leave the blood and diffuse into the air sacs, where they are exhaled through the lungs. This gas exchange is passive: oxygen goes from the higher concentration in the lungs to the lower concentration in the blood. Similarly, carbon dioxide goes from the blood to the lungs.
Image by TheVisualMD
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Alveoli of Lung Expanding and Contracting During Breathing
Animation showing alveoli of the lungs expanding and contracting back during breathing
Video by TheVisualMD
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Capillary Blood Flow Around Alveoli
Camera looks straight on to show blood flowing through a capillary surrounding alveoli in the lungs as they expand and contract during breathing
Video by TheVisualMD
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Alveoli Capillary
Still camera shot showing the capillaries that surround the alveoli in the lungs as they expand with air and then contract again during breathing
Video by TheVisualMD
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Alveoli of Lung Expanding and Contracting During Breathing
Animation showing alveoli expanding and contracting back during breaths
Video by TheVisualMD
Systems of Gas Exchange
Air enters the respiratory system through the nasal cavity and pharynx, and then passes through the trachea and into the bronchi, which bring air into the lungs. (credit: modification of work by NCI)
Image by CNX Openstax (credit: modification of work by NCI)
Pneumonia - Cross Section of Alveoli filled with fluid
Pneumonia - Cross Section of Alveoli filled with fluid
Image by TheVisualMD
Bronchus Leading into Alveolar Sac and Surrounding Capillary
The main airways of the lungs (bronchi) branch off into smaller passageways called bronchioles. At the end of the bronchioles are tiny air sacs called alveoli, which are the \"leaves\" of the respiratory tree and the site of gas exchange. The membranes between alveoli and the capillaries that surround them are extremely thin. Oxygen diffuses through these membranes into the capillaries and carbon dioxide follows the reverse course. Red blood cells deliver oxygen to tissues throughout the body and then carry carbon dioxide from those cells back to the lungs.
Image by TheVisualMD
Alveolus and Surrounding Capillary
Illustration of an alveolus and capillary. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery and veins are the only vessels that break the rules about arteries carrying oxygenated blood and veins carrying deoxygenated blood. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein. Each alveolar sac, or air sac, is surrounded by a bed of capillaries, and the walls between the lung and the capillary are extremely thin. The walls are so delicate, in fact, that the inhaled oxygen seep from the air sacs to bind to the hemoglobin in the blood, while the carbon dioxide and other waste gasses leave the blood and diffuse into the lungs where they can be exhaled. The gas exchange is passive; oxygen goes from the lungs into the blood because that's where the concentration is lower. While this is normally an effective way of bringing in oxygen and exhaling waste gases, any toxic gasses, such as carbon monoxide, that a person inhales can enter the blood in the same way.
Image by TheVisualMD
Alveolar Type II Cells Secreting Surfactant
The walls of the alveoli, the tiny air sacs within the lungs where the exchange of oxygen and carbon dioxide takes place, are lined with three major alveolar cells. These are: Type I (squamous alveolar) cells, Type II (great alveolar) cells, and the third type, magrophages. Type II cells secrete pulmonary surfactant, which lowers the surface tension of water and allows the membrane to separate, thereby increasing the capability to exchange gases and reducing fluid accumulation in the alveolus. Premature infants sometimes have a developmental insufficiency of surfactant production and structural immaturity in the lungs.This results in infant respiratory distress syndrome (IRDS).
Image by TheVisualMD
Bronchi and Bronchioles in Lungs
Your lungs are the only internal organs of your body that are constantly exposed to the outside world-that is, the air you breathe. Air contains oxygen, the vital gas that fuels all your metabolic processes. But air can also contain pollutants, irritants, and allergens. When you inhale, air passes down the back of your throat, past your vocal cords, and into your windpipe, or trachea. Your trachea divides into twin air pipes (one for each lung) called the bronchi. Much the way in which a tree branches, the bronchi continue to divide into smaller air passages called bronchioles. Collectively, these air passages are known as the airways. The bronchioles continue to branch until they become extremely narrow-the small airways are less than 2 micrometers in diameter! They end in microscopic air sacs called alveoli. Your lungs contain about 500 million alveoli.
Image by TheVisualMD
Pulmonary alveolus
An alveolus (plural: alveoli, from Latin alveus, "little cavity"), is an anatomical structure that has the form of a hollow cavity. Mainly found in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with the blood.
Image by LadyofHats
Carbon Dioxide: Alveoli
The alveoli are the tiny, capillary-rich air sacs that cover the branching structure of the lungs and make gas exchange possible. A change in the respiratory rate alters the amount of CO2 exhaled, which in turn can affect blood pH in minutes.
Image by TheVisualMD
Normal Bronchiole
When you inhale, air passes down the back of your throat, past your vocal cords, and into your windpipe, or trachea. Your trachea divides into twin air pipes (one for each lung) called the bronchi. Much the way in which a tree branches, the bronchi continue to divide into smaller air passages called bronchioles. Collectively, these air passages are known as the airways. The bronchioles continue to branch until they become extremely narrow-the small airways are less than 2 micrometers in diameter! They end in microscopic air sacs called alveoli. Your lungs contain about 500 million alveoli.
If the inflammation of asthma is uncontrolled, the result may be lasting physical changes to the structure of the cells and tissues of your lungs. The walls of the airways may thicken and the interior of your airways narrow permanently, in a way that medications can't help. This is especially true if your asthma is severe. This process is called airway remodeling.
Image by TheVisualMD
Male Thorax Showing Trachea and Lung
3D visualization of an anterior view of the lungs and heart reconstructed from scanned human data. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
Carbon Dioxide exchange in the Alveoli
TheVisualMD
5:16
Overview of the Respiratory System, Animation
Alila Medical Media/YouTube
Alveoli of Lung
TheVisualMD
Your lung is a living breathing miracle
TheVisualMD
Systems of Gas Exchange
CNX Openstax (credit: modification of work by Mariana Ruiz Villareal)
Heart pulmonary and great vessels
TheVisualMD
Fluid-Filled Alveoli Within the Lungs
TheVisualMD
Fluid-Filled Alveoli Within the Lungs
TheVisualMD
Lung with Visible Bronchi and Bronchiole
TheVisualMD
0:12
Alveoli of Lung Expanding and Contracting During Breathing
TheVisualMD
0:10
Capillary Blood Flow Around Alveoli
TheVisualMD
0:16
Alveoli Capillary
TheVisualMD
0:12
Alveoli of Lung Expanding and Contracting During Breathing
TheVisualMD
Systems of Gas Exchange
CNX Openstax (credit: modification of work by NCI)
Pneumonia - Cross Section of Alveoli filled with fluid
TheVisualMD
Bronchus Leading into Alveolar Sac and Surrounding Capillary
TheVisualMD
Alveolus and Surrounding Capillary
TheVisualMD
Alveolar Type II Cells Secreting Surfactant
TheVisualMD
Bronchi and Bronchioles in Lungs
TheVisualMD
Pulmonary alveolus
LadyofHats
Carbon Dioxide: Alveoli
TheVisualMD
Normal Bronchiole
TheVisualMD
Male Thorax Showing Trachea and Lung
TheVisualMD
Gas Exchange
Carbon Dioxide exchange in the Alveoli
Image by TheVisualMD
Carbon Dioxide exchange in the Alveoli
Carbon Dioxide exchange in the Alveoli - Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. (NCBI/NLM/NIH)
Image by TheVisualMD
Gas Exchange
The purpose of the respiratory system is to perform gas exchange. Pulmonary ventilation provides air to the alveoli for this gas exchange process. At the respiratory membrane, where the alveolar and capillary walls meet, gases move across the membranes, with oxygen entering the bloodstream and carbon dioxide exiting. It is through this mechanism that blood is oxygenated and carbon dioxide, the waste product of cellular respiration, is removed from the body.
Gas Exchange
Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up. External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues. The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes. Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs.
External Respiration
The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries. These pulmonary capillaries create the respiratory membrane with the alveoli (image). As the blood is pumped through this capillary network, gas exchange occurs. Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes (red blood cells) and binds to a protein called hemoglobin, a process described later in this chapter. Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli. Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter.
External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries.
External Respiration
In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus.
Although the solubility of oxygen in blood is not high, there is a drastic difference in the partial pressure of oxygen in the alveoli versus in the blood of the pulmonary capillaries. This difference is about 64 mm Hg: The partial pressure of oxygen in the alveoli is about 104 mm Hg, whereas its partial pressure in the blood of the capillary is about 40 mm Hg. This large difference in partial pressure creates a very strong pressure gradient that causes oxygen to rapidly cross the respiratory membrane from the alveoli into the blood.
The partial pressure of carbon dioxide is also different between the alveolar air and the blood of the capillary. However, the partial pressure difference is less than that of oxygen, about 5 mm Hg. The partial pressure of carbon dioxide in the blood of the capillary is about 45 mm Hg, whereas its partial pressure in the alveoli is about 40 mm Hg. However, the solubility of carbon dioxide is much greater than that of oxygen—by a factor of about 20—in both blood and alveolar fluids. As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar.
Internal Respiration
Internal respiration is gas exchange that occurs at the level of body tissues (image). Similar to external respiration, internal respiration also occurs as simple diffusion due to a partial pressure gradient. However, the partial pressure gradients are opposite of those present at the respiratory membrane. The partial pressure of oxygen in tissues is low, about 40 mm Hg, because oxygen is continuously used for cellular respiration. In contrast, the partial pressure of oxygen in the blood is about 100 mm Hg. This creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuse out of the blood, cross the interstitial space, and enter the tissue. Hemoglobin that has little oxygen bound to it loses much of its brightness, so that blood returning to the heart is more burgundy in color.
Considering that cellular respiration continuously produces carbon dioxide, the partial pressure of carbon dioxide is lower in the blood than it is in the tissue, causing carbon dioxide to diffuse out of the tissue, cross the interstitial fluid, and enter the blood. It is then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form. By the time blood returns to the heart, the partial pressure of oxygen has returned to about 40 mm Hg, and the partial pressure of carbon dioxide has returned to about 45 mm Hg. The blood is then pumped back to the lungs to be oxygenated once again during external respiration.
Internal Respiration
Oxygen diffuses out of the capillary and into cells, whereas carbon dioxide diffuses out of cells and into the capillary.
EVERYDAY CONNECTION
Hyperbaric Chamber TreatmentA type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment. A hyperbaric chamber is a unit that can be sealed and expose a patient to either 100 percent oxygen with increased pressure or a mixture of gases that includes a higher concentration of oxygen than normal atmospheric air, also at a higher partial pressure than the atmosphere. There are two major types of chambers: monoplace and multiplace. Monoplace chambers are typically for one patient, and the staff tending to the patient observes the patient from outside of the chamber (Figure). Some facilities have special monoplace hyperbaric chambers that allow multiple patients to be treated at once, usually in a sitting or reclining position, to help ease feelings of isolation or claustrophobia. Multiplace chambers are large enough for multiple patients to be treated at one time, and the staff attending these patients is present inside the chamber. In a multiplace chamber, patients are often treated with air via a mask or hood, and the chamber is pressurized.
Hyperbaric Chamber
(credit: “komunews”/flickr.com)
Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure. In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream. At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair. Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures.
Overview
The behavior of gases can be explained by the principles of Dalton’s law and Henry’s law, both of which describe aspects of gas exchange. Dalton’s law states that each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture. Henry’s law states that the amount of a specific gas that dissolves in a liquid is a function of its partial pressure. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar.
Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries. Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli. If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation. External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences.
Source: CNX OpenStax
Additional Materials (31)
Red Blood Cell in Capillary
The cardiovascular system is vast network of arteries, veins and vessels that would extend 60,000 miles if stretched end-to-end. All but a tiny fraction of this vessel network is invisible to the naked eye. The smallest capillaries (from latin "hairlike") are so narrow that red blood cells must pass through in single file. Higher than normal blood iron levels have been linked to heart disease and the reason is believed to be the oxidative stress the excess iron places on the walls of the blood vessels. It is the biological counterpart of rust. There are 20-30 trillion red blood cells (RBCs) in an adult's body. The life span of RBCs, which are produced in bone marrow, is about 100 days, which means that 2 million die (and are replaced) each second, but in that short lifetime they can make 75,000 round trips between lungs, heart and tissues in the body.
Image by TheVisualMD
Respiration Gas Exchange
Video by Armando Hasudungan/YouTube
Red Blood Cells Carry Oxygen
This video focuses on one of the main components of blood, the red blood cell and its function to carry oxygen. The video begins with revealing the red blood cells and the heart that pumps the oxygenated blood to the rest of the body. Hemoglobin is the protein molecule found in these red blood cells that enable blood to transport oxygen. If the blood's capacity to transport oxygen to the tissues is reduced due to a decrease in the number of red blood cells, anemia may occur.
Image by TheVisualMD
Your Brain Needs Oxygen
Your brain is hungry. It's your body's single largest consumer of oxygen. Although your brain represents only about 2% of your body's weight, it utilizes about 20% of your body's blood. Brain cells are particularly vulnerable to a decrease of oxygen supply to the brain (termed hypoxia). Normally, brain cells don't come into contact with the blood. They are isolated by a layer of cells called the blood-brain barrier. If they don't get the oxygen or nutrients they require, or if they come into contact with blood, brain cells start to die in minutes. That's exactly what happens when someone has a stroke. When an artery to the brain becomes blocked or ruptures, the affected areas of brain tissue become damaged or die.
Image by TheVisualMD
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Male with Visible Heart Measuring Oxygen Consumption (VO2)
Video begins with a Micro Magnetic Resonance Imaging based visualization of a beating heart in a the thorax. The camera zooms out to the thorax to show Brandon Leslie running either on the spot or on a treadmill within a test room The camera pans up to his face where he is attached to equipement used to show measure his oxygyen consumption.
Video by TheVisualMD
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Hemoglobin Within Red Blood Cell (RBC)
A red blood cell rushes toward the camera, the camera enters the cell to focus on all of the hemoglobin molecules within
Video by TheVisualMD
You Need Aerobic Exercise
Running, swimming, rowing and brisk walking are aerobic exercises, the oxygen-powered activities that strengthen our cardiovascular system, increase our endurance, and burn fat. During aerobic exercise, we use oxygen to efficiently transform nutrients into large amounts of fuel.
Image by TheVisualMD
Pneumonia - Cross Section of Alveoli filled with fluid
Pneumonia - Cross Section of Alveoli filled with fluid
Image by TheVisualMD
Alveoli of Lung
When you breathe, oxygenated air flows through your lungs and ends up in thousands of small air sacs in the lungs called alveoli. The right side of your heart sends deoxygenated blood to the capillaries surrounding these alveoli. The walls between the alveoli and the capillaries are extremely thin, so that the inhaled oxygen can seep from the air sacs to bind to the hemoglobin molecules in the erythrocytes. Carbon dioxide and other waste gases leave the blood and diffuse into the air sacs, where they are exhaled through the lungs. This gas exchange is passive: oxygen goes from the higher concentration in the lungs to the lower concentration in the blood. Similarly, carbon dioxide goes from the blood to the lungs.
Image by TheVisualMD
Capillary in Alveolus
This is a magnified section of capillaries in an aveolus. Capillaries are the smallest blood vessels in the body. The walls of the capillaries are the primary sites for gas and nutrition exchange.
Image by TheVisualMD
Pulmonary Alveolus
The normal alveolus (Left-Hand Side) and the injured alveolus in the acute phase of acute lung injury and the acute respiratory distress syndrome (Right-Hand Side)
Image by https://www.researchgate.net/figure/230654786_fig5_Figure-1-The-normal-alveolus-Left-Hand-Side-and-the-injured-alveolus-in-the-acute
The normal alveolus (Left-Hand Side) and the injured alveolus in the acute phase of acute lung injury and the acute respiratory distress syndrome.
The normal alveolus (Left-Hand Side) and the injured alveolus in the acute phase of acute lung injury and the acute respiratory distress syndrome (Right-Hand Side)
Image by S.SANJANA
Alveolus and Surrounding Capillary
Illustration of an alveolus and capillary. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery and veins are the only vessels that break the rules about arteries carrying oxygenated blood and veins carrying deoxygenated blood. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein. Each alveolar sac, or air sac, is surrounded by a bed of capillaries, and the walls between the lung and the capillary are extremely thin. The walls are so delicate, in fact, that the inhaled oxygen seep from the air sacs to bind to the hemoglobin in the blood, while the carbon dioxide and other waste gasses leave the blood and diffuse into the lungs where they can be exhaled. The gas exchange is passive; oxygen goes from the lungs into the blood because that's where the concentration is lower. While this is normally an effective way of bringing in oxygen and exhaling waste gases, any toxic gasses, such as carbon monoxide, that a person inhales can enter the blood in the same way.
Terminal bronchioles are connected by respiratory bronchioles to alveolar ducts and alveolar sacs. Each alveolar sac contains 20 to 30 spherical alveoli and has the appearance of a bunch of grapes. Air flows into the atrium of the alveolar sac, then circulates into alveoli where gas exchange occurs with the capillaries. Mucous glands secrete mucous into the airways, keeping them moist and flexible. (credit: modification of work by Mariana Ruiz Villareal)
Image by CNX Openstax (credit: modification of work by Mariana Ruiz Villareal)
External Respiration
In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus.
Image by CNX Openstax
Fluid Filled Alveoli
This image shows a fluid-filled alveoli within the lungs. The alveolus (singular) is the smallest unit of the lungs. It is the site of gas exchange with the capillaries. Oxygen and carbon dioxide move between the alveoli to the surrounding capillaries.
Image by TheVisualMD
Pulmonary alveolus
Pulmonary alveolus : Bronchial anatomy detail of alveoli and lung circulation.
Image by Patrick J. Lynch, medical illustrator
Systems of Gas Exchange
Air enters the respiratory system through the nasal cavity and pharynx, and then passes through the trachea and into the bronchi, which bring air into the lungs. (credit: modification of work by NCI)
Image by CNX Openstax (credit: modification of work by NCI)
Respiratory System - Alveolus and Surrounding Capillary of Lung
3D visualization reconstructed from scanned human data of the heart and airways of the lungs. De-oxygenated red blood cells are sent by the right side of the heart through the pulmonary artery into the vessels of the lungs to be refilled with oxygen for their next circuit through the body. The blood is carried through the lung tissues, where it exchanges its carbon dioxide for oxygen in the alveoli. It is then returned through the pulmonary veins to the left side of the heart and sent out to the rest of the body. The pulmonary artery and veins are the only vessels that break the rules about arteries carrying oxygenated blood and veins carrying deoxygenated blood. Technically arteries carry blood away from the heart, and veins carry it back. Everywhere else in the body, blood flowing away from the heart is oxygenated, and blood flowing back to the heart is deoxygenated, but not in the lungs. The pulmonary artery carries away the deoxygenated blood, which returns fully oxygenated through the pulmonary vein.
Image by TheVisualMD
Bronchus Leading into Alveolar Sac and Surrounding Capillary
The main airways of the lungs (bronchi) branch off into smaller passageways called bronchioles. At the end of the bronchioles are tiny air sacs called alveoli, which are the \"leaves\" of the respiratory tree and the site of gas exchange. The membranes between alveoli and the capillaries that surround them are extremely thin. Oxygen diffuses through these membranes into the capillaries and carbon dioxide follows the reverse course. Red blood cells deliver oxygen to tissues throughout the body and then carry carbon dioxide from those cells back to the lungs.
Image by TheVisualMD
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Human Body Revealing Alveoli Within Lung
Camera zooms in on visible human with arms extended upwards, begins with only the circulatory system, lungs, and kidneys showing The skeleton fades in, and the lungs are contracting and expanding to demonstrate the movements associated with breathing. The camera then zooms into the lungs to focus on the alveoli within
Video by TheVisualMD
Fluid-Filled Alveoli Within the Lungs
In pulmonary edema, also known as congestive heart failure, fluid fills the alveoli (air sacs) of the lungs. This can occur when a ventricular arrhythmia causes the left ventricle to be unable to pump out enough of the blood it receives from the lungs, or when the right ventricle can't overcome increased pressure in the pulmonary artery due to left heart failure.
Image by TheVisualMD
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Alveoli Capillary
Still camera shot showing the capillaries that surround the alveoli in the lungs as they expand with air and then contract again during breathing
Video by TheVisualMD
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Capillary Blood Flow Around Alveoli
Camera looks straight on to show blood flowing through a capillary surrounding alveoli in the lungs as they expand and contract during breathing
Video by TheVisualMD
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Alveoli of Lung Expanding and Contracting During Breathing
Animation showing alveoli of the lungs expanding and contracting back during breathing
Video by TheVisualMD
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Alveoli of Lung Expanding and Contracting During Breathing
Animation showing alveoli expanding and contracting back during breaths
The normal alveolus (Left-Hand Side) and the injured alveolus in the acute phase of acute lung injury and the acute respiratory distress syndrome.
S.SANJANA
Alveolus and Surrounding Capillary
TheVisualMD
Structures of the Respiratory Zone
CNX Openstax
Systems of Gas Exchange
CNX Openstax (credit: modification of work by Mariana Ruiz Villareal)
External Respiration
CNX Openstax
Fluid Filled Alveoli
TheVisualMD
Pulmonary alveolus
Patrick J. Lynch, medical illustrator
Systems of Gas Exchange
CNX Openstax (credit: modification of work by NCI)
Respiratory System - Alveolus and Surrounding Capillary of Lung
TheVisualMD
Bronchus Leading into Alveolar Sac and Surrounding Capillary
TheVisualMD
0:15
Human Body Revealing Alveoli Within Lung
TheVisualMD
Fluid-Filled Alveoli Within the Lungs
TheVisualMD
0:16
Alveoli Capillary
TheVisualMD
0:10
Capillary Blood Flow Around Alveoli
TheVisualMD
0:12
Alveoli of Lung Expanding and Contracting During Breathing
TheVisualMD
0:12
Alveoli of Lung Expanding and Contracting During Breathing
TheVisualMD
Alveoli
Pseudostratified Ciliated Columnar Epithelium
CNX Openstax
Respiratory Zone
CNX Openstax
Trachea
CNX Openstax
Transport of Gases
Your blood vessels are the body's superhighway
Image by TheVisualMD
Your blood vessels are the body's superhighway
Your blood vessels are the body's superhighway. Blood races through more than 50,000 miles of vessels, delivering nutrients to cells and hauling waste products away from them. One of the blood's most vital passengers is oxygen. Oxygen binds to hemoglobin, a protein in red blood cells, and is carried to cells throughout the body. Anemia occurs when hemoglobin does not carry enough oxygen to cells. There are several possible causes. Sometimes the body has too little iron, which is essential to the formation of hemoglobin. Deficiencies of vitamin B-12 or folic acid can also cause anemia. Sometimes there are not enough red blood cells, which can result from ulcers or other undetected sources of blood loss. And sometimes the body simply demands more iron for growth: Pregnant women and growing toddlers are at increased risk of anemia. People who are anemic can have headaches, dizziness, difficulty breathing, fatigue and they may feel cold. Anyone who has such symptoms can find out, through a simple blood test, whether some form of anemia is to blame. To keep that superhighway moving, we have to make sure that the blood is doing its job.
Image by TheVisualMD
Transport of Gases
The other major activity in the lungs is the process of respiration, the process of gas exchange. The function of respiration is to provide oxygen for use by body cells during cellular respiration and to eliminate carbon dioxide, a waste product of cellular respiration, from the body. In order for the exchange of oxygen and carbon dioxide to occur, both gases must be transported between the external and internal respiration sites. Although carbon dioxide is more soluble than oxygen in blood, both gases require a specialized transport system for the majority of the gas molecules to be moved between the lungs and other tissues.
Even though oxygen is transported via the blood, you may recall that oxygen is not very soluble in liquids. A small amount of oxygen does dissolve in the blood and is transported in the bloodstream, but it is only about 1.5% of the total amount. The majority of oxygen molecules are carried from the lungs to the body’s tissues by a specialized transport system, which relies on the erythrocyte—the red blood cell. Erythrocytes contain a metalloprotein, hemoglobin, which serves to bind oxygen molecules to the erythrocyte (image). Heme is the portion of hemoglobin that contains iron, and it is heme that binds oxygen. One hemoglobin molecule contains iron-containing Heme molecules, and because of this, each hemoglobin molecule is capable of carrying up to four molecules of oxygen. As oxygen diffuses across the respiratory membrane from the alveolus to the capillary, it also diffuses into the red blood cell and is bound by hemoglobin. The following reversible chemical reaction describes the production of the final product, oxyhemoglobin (Hb–O2), which is formed when oxygen binds to hemoglobin. Oxyhemoglobin is a bright red-colored molecule that contributes to the bright red color of oxygenated blood.
Erythrocyte and Hemoglobin
Hemoglobin consists of four subunits, each of which contains one molecule of iron.
Function of Hemoglobin
Hemoglobin is composed of subunits, a protein structure that is referred to as a quaternary structure. Each of the four subunits that make up hemoglobin is arranged in a ring-like fashion, with an iron atom covalently bound to the heme in the center of each subunit. Binding of the first oxygen molecule causes a conformational change in hemoglobin that allows the second molecule of oxygen to bind more readily. As each molecule of oxygen is bound, it further facilitates the binding of the next molecule, until all four heme sites are occupied by oxygen. The opposite occurs as well: After the first oxygen molecule dissociates and is “dropped off” at the tissues, the next oxygen molecule dissociates more readily. When all four heme sites are occupied, the hemoglobin is said to be saturated. When one to three heme sites are occupied, the hemoglobin is said to be partially saturated. Therefore, when considering the blood as a whole, the percent of the available heme units that are bound to oxygen at a given time is called hemoglobin saturation. Hemoglobin saturation of 100 percent means that every heme unit in all of the erythrocytes of the body is bound to oxygen. In a healthy individual with normal hemoglobin levels, hemoglobin saturation generally ranges from 95 percent to 99 percent.
Oxygen Dissociation from Hemoglobin
Partial pressure is an important aspect of the binding of oxygen to and disassociation from heme. An oxygen–hemoglobin dissociation curve is a graph that describes the relationship of partial pressure to the binding of oxygen to heme and its subsequent dissociation from heme (image). Remember that gases travel from an area of higher partial pressure to an area of lower partial pressure. In addition, the affinity of an oxygen molecule for heme increases as more oxygen molecules are bound. Therefore, in the oxygen–hemoglobin saturation curve, as the partial pressure of oxygen increases, a proportionately greater number of oxygen molecules are bound by heme. Not surprisingly, the oxygen–hemoglobin saturation/dissociation curve also shows that the lower the partial pressure of oxygen, the fewer oxygen molecules are bound to heme. As a result, the partial pressure of oxygen plays a major role in determining the degree of binding of oxygen to heme at the site of the respiratory membrane, as well as the degree of dissociation of oxygen from heme at the site of body tissues.
Oxygen-Hemoglobin Dissociation and Effects of pH and Temperature
These three graphs show (a) the relationship between the partial pressure of oxygen and hemoglobin saturation, (b) the effect of pH on the oxygen–hemoglobin dissociation curve, and (c) the effect of temperature on the oxygen–hemoglobin dissociation curve.
The mechanisms behind the oxygen–hemoglobin saturation/dissociation curve also serve as automatic control mechanisms that regulate how much oxygen is delivered to different tissues throughout the body. This is important because some tissues have a higher metabolic rate than others. Highly active tissues, such as muscle, rapidly use oxygen to produce ATP, lowering the partial pressure of oxygen in the tissue to about 20 mm Hg. The partial pressure of oxygen inside capillaries is about 100 mm Hg, so the difference between the two becomes quite high, about 80 mm Hg. As a result, a greater number of oxygen molecules dissociate from hemoglobin and enter the tissues. The reverse is true of tissues, such as adipose (body fat), which have lower metabolic rates. Because less oxygen is used by these cells, the partial pressure of oxygen within such tissues remains relatively high, resulting in fewer oxygen molecules dissociating from hemoglobin and entering the tissue interstitial fluid. Although venous blood is said to be deoxygenated, some oxygen is still bound to hemoglobin in its red blood cells. This provides an oxygen reserve that can be used when tissues suddenly demand more oxygen.
Factors other than partial pressure also affect the oxygen–hemoglobin saturation/dissociation curve. For example, a higher temperature promotes hemoglobin and oxygen to dissociate faster, whereas a lower temperature inhibits dissociation (see image, middle). However, the human body tightly regulates temperature, so this factor may not affect gas exchange throughout the body. The exception to this is in highly active tissues, which may release a larger amount of energy than is given off as heat. As a result, oxygen readily dissociates from hemoglobin, which is a mechanism that helps to provide active tissues with more oxygen.
Certain hormones, such as androgens, epinephrine, thyroid hormones, and growth hormone, can affect the oxygen–hemoglobin saturation/disassociation curve by stimulating the production of a compound called 2,3-bisphosphoglycerate (BPG) by erythrocytes. BPG is a byproduct of glycolysis. Because erythrocytes do not contain mitochondria, glycolysis is the sole method by which these cells produce ATP. BPG promotes the disassociation of oxygen from hemoglobin. Therefore, the greater the concentration of BPG, the more readily oxygen dissociates from hemoglobin, despite its partial pressure.
The pH of the blood is another factor that influences the oxygen–hemoglobin saturation/dissociation curve (see image). The Bohr effect is a phenomenon that arises from the relationship between pH and oxygen’s affinity for hemoglobin: A lower, more acidic pH promotes oxygen dissociation from hemoglobin. In contrast, a higher, or more basic, pH inhibits oxygen dissociation from hemoglobin. The greater the amount of carbon dioxide in the blood, the more molecules that must be converted, which in turn generates hydrogen ions and thus lowers blood pH. Furthermore, blood pH may become more acidic when certain byproducts of cell metabolism, such as lactic acid, carbonic acid, and carbon dioxide, are released into the bloodstream.
Hemoglobin of the Fetus
The fetus has its own circulation with its own erythrocytes; however, it is dependent on the mother for oxygen. Blood is supplied to the fetus by way of the umbilical cord, which is connected to the placenta and separated from maternal blood by the chorion. The mechanism of gas exchange at the chorion is similar to gas exchange at the respiratory membrane. However, the partial pressure of oxygen is lower in the maternal blood in the placenta, at about 35 to 50 mm Hg, than it is in maternal arterial blood. The difference in partial pressures between maternal and fetal blood is not large, as the partial pressure of oxygen in fetal blood at the placenta is about 20 mm Hg. Therefore, there is not as much diffusion of oxygen into the fetal blood supply. The fetus’ hemoglobin overcomes this problem by having a greater affinity for oxygen than maternal hemoglobin (image). Both fetal and adult hemoglobin have four subunits, but two of the subunits of fetal hemoglobin have a different structure that causes fetal hemoglobin to have a greater affinity for oxygen than does adult hemoglobin.
Oxygen-Hemoglobin Dissociation Curves in Fetus and Adult
Fetal hemoglobin has a greater affinity for oxygen than does adult hemoglobin.
Carbon Dioxide Transport in the Blood
Carbon dioxide is transported by three major mechanisms. The first mechanism of carbon dioxide transport is by blood plasma, as some carbon dioxide molecules dissolve in the blood. The second mechanism is transport in the form of bicarbonate (HCO3–), which also dissolves in plasma. The third mechanism of carbon dioxide transport is similar to the transport of oxygen by erythrocytes (image).
Carbon Dioxide Transport
Carbon dioxide is transported by three different methods: (a) in erythrocytes; (b) after forming carbonic acid (H2CO3 ), which is dissolved in plasma; (c) and in plasma.
Dissolved Carbon Dioxide
Although carbon dioxide is not considered to be highly soluble in blood, a small fraction—about 7 to 10 percent—of the carbon dioxide that diffuses into the blood from the tissues dissolves in plasma. The dissolved carbon dioxide then travels in the bloodstream and when the blood reaches the pulmonary capillaries, the dissolved carbon dioxide diffuses across the respiratory membrane into the alveoli, where it is then exhaled during pulmonary ventilation.
Bicarbonate Buffer
A large fraction—about 70 percent—of the carbon dioxide molecules that diffuse into the blood is transported to the lungs as bicarbonate. Most bicarbonate is produced in erythrocytes after carbon dioxide diffuses into the capillaries, and subsequently into red blood cells. Carbonic anhydrase (CA) causes carbon dioxide and water to form carbonic acid (H2CO3), which dissociates into two ions: bicarbonate (HCO3–) and hydrogen (H+).
Bicarbonate tends to build up in the erythrocytes, so that there is a greater concentration of bicarbonate in the erythrocytes than in the surrounding blood plasma. As a result, some of the bicarbonate will leave the erythrocytes and move down its concentration gradient into the plasma in exchange for chloride (Cl–) ions. This phenomenon is referred to as the chloride shift and occurs because by exchanging one negative ion for another negative ion, neither the electrical charge of the erythrocytes nor that of the blood is altered.
At the pulmonary capillaries, the chemical reaction that produced bicarbonate (shown above) is reversed, and carbon dioxide and water are the products. Much of the bicarbonate in the plasma re-enters the erythrocytes in exchange for chloride ions. Hydrogen ions and bicarbonate ions join to form carbonic acid, which is converted into carbon dioxide and water by carbonic anhydrase. Carbon dioxide diffuses out of the erythrocytes and into the plasma, where it can further diffuse across the respiratory membrane into the alveoli to be exhaled during pulmonary ventilation.
Carbaminohemoglobin
About 20 percent of carbon dioxide is bound by hemoglobin and is transported to the lungs. Carbon dioxide does not bind to iron as oxygen does; instead, carbon dioxide binds amino acid moieties on the globin portions of hemoglobin to form carbaminohemoglobin, which forms when hemoglobin and carbon dioxide bind. When hemoglobin is not transporting oxygen, it tends to have a bluish-purple tone to it, creating the darker maroon color typical of deoxygenated blood.
Similar to the transport of oxygen by heme, the binding and dissociation of carbon dioxide to and from hemoglobin is dependent on the partial pressure of carbon dioxide. Because carbon dioxide is released from the lungs, blood that leaves the lungs and reaches body tissues has a lower partial pressure of carbon dioxide than is found in the tissues. As a result, carbon dioxide leaves the tissues because of its higher partial pressure, enters the blood, and then moves into red blood cells, binding to hemoglobin. In contrast, in the pulmonary capillaries, the partial pressure of carbon dioxide is high compared to within the alveoli. As a result, carbon dioxide dissociates readily from hemoglobin and diffuses across the respiratory membrane into the air.
In addition to the partial pressure of carbon dioxide, the oxygen saturation of hemoglobin and the partial pressure of oxygen in the blood also influence the affinity of hemoglobin for carbon dioxide. The Haldane effect is a phenomenon that arises from the relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide. Hemoglobin that is saturated with oxygen does not readily bind carbon dioxide. However, when oxygen is not bound to heme and the partial pressure of oxygen is low, hemoglobin readily binds to carbon dioxide.
Overview
Oxygen is primarily transported through the blood by erythrocytes. These cells contain a metalloprotein called hemoglobin, which is composed of four subunits with a ring-like structure. Each subunit contains one atom of iron bound to a molecule of heme. Heme binds oxygen so that each hemoglobin molecule can bind up to four oxygen molecules. When all of the heme units in the blood are bound to oxygen, hemoglobin is considered to be saturated. Hemoglobin is partially saturated when only some heme units are bound to oxygen. An oxygen–hemoglobin saturation/dissociation curve is a common way to depict the relationship of how easily oxygen binds to or dissociates from hemoglobin as a function of the partial pressure of oxygen. As the partial pressure of oxygen increases, the more readily hemoglobin binds to oxygen. At the same time, once one molecule of oxygen is bound by hemoglobin, additional oxygen molecules more readily bind to hemoglobin. Other factors such as temperature, pH, the partial pressure of carbon dioxide, and the concentration of 2,3-bisphosphoglycerate can enhance or inhibit the binding of hemoglobin and oxygen as well. Fetal hemoglobin has a different structure than adult hemoglobin, which results in fetal hemoglobin having a greater affinity for oxygen than adult hemoglobin.
Carbon dioxide is transported in blood by three different mechanisms: as dissolved carbon dioxide, as bicarbonate, or as carbaminohemoglobin. A small portion of carbon dioxide remains. The largest amount of transported carbon dioxide is as bicarbonate, formed in erythrocytes. For this conversion, carbon dioxide is combined with water with the aid of an enzyme called carbonic anhydrase. This combination forms carbonic acid, which spontaneously dissociates into bicarbonate and hydrogen ions. As bicarbonate builds up in erythrocytes, it is moved across the membrane into the plasma in exchange for chloride ions by a mechanism called the chloride shift. At the pulmonary capillaries, bicarbonate re-enters erythrocytes in exchange for chloride ions, and the reaction with carbonic anhydrase is reversed, recreating carbon dioxide and water. Carbon dioxide then diffuses out of the erythrocyte and across the respiratory membrane into the air. An intermediate amount of carbon dioxide binds directly to hemoglobin to form carbaminohemoglobin. The partial pressures of carbon dioxide and oxygen, as well as the oxygen saturation of hemoglobin, influence how readily hemoglobin binds carbon dioxide. The less saturated hemoglobin is and the lower the partial pressure of oxygen in the blood is, the more readily hemoglobin binds to carbon dioxide. This is an example of the Haldane effect.
Source: CNX OpenStax
Additional Materials (6)
Life Cycle of Red Blood Cell
We have a total of 20 to 30 trillion RBCs in the body and to maintain the body's healthy equilibrium, about 2.5 million RBCs are destroyed and replaced every second. In early development, RBC production begins in the yolk sac, shifts to the liver and spleen during the 3rd month of gestation, and finally to the bone marrow in the 5th month. Once adulthood is reached, the creation of RBCs is mostly restricted to the marrow from the ends of the \"long\" bones-the vertebrae, ribs, and pelvis-with a little produced in the skull. The life cycle of a normal RBC is about 120 days, just four months. But in that short lifetime the RBC makes an astonishing 75,000 round trips between the lungs, heart and cells of the body. Since RBCs do not possess a nucleus, they are unable to repair or synthesize new cellular components and eventually they wear out. When that happens, most aging RBCs are pulled out of circulation by specialized white blood cells called macrophages within the liver, spleen, and lymph nodes. The macrophages engulf RBCs, \"digest\" them and release some of their components to be recycled within the body. As old RBCs are broken down and their components re-utilized, the bone marrow is constantly at work producing new RBCs. In a healthy human being, this is a dynamic and continuous process.
Image by TheVisualMD
Biology Help: The Respiratory System - Gas Exchange In The Alveoli Explained In 2 Minutes!!
Video by 5MinuteSchool/YouTube
Hemoglobin
(a) A molecule of hemoglobin contains four globin proteins, each of which is bound to one molecule of the iron-containing pigment heme. (b) A single erythrocyte can contain 300 million hemoglobin molecules, and thus more than 1 billion oxygen molecules.
Image by CNX Openstax
A computer graphics depiction of a human red blood cell on a glass surface.
A computer graphics depiction of a human red blood cell on a glass surface.
Image by Rogeriopfm
Red Blood Cell Development
This video explains red blood cell development, following a pluripotent stem cell to red blood cell.
Image by TheVisualMD
Erythrocyte and Hemoglobin
Hemoglobin consists of four subunits, each of which contains one molecule of iron.
Image by CNX Openstax
Life Cycle of Red Blood Cell
TheVisualMD
1:54
Biology Help: The Respiratory System - Gas Exchange In The Alveoli Explained In 2 Minutes!!
5MinuteSchool/YouTube
Hemoglobin
CNX Openstax
A computer graphics depiction of a human red blood cell on a glass surface.
Rogeriopfm
Red Blood Cell Development
TheVisualMD
Erythrocyte and Hemoglobin
CNX Openstax
Modifications in Respiratory Functions
Biology of ventilation
Image by Eleanor Lutz and Sarah Low
Biology of ventilation
An animated diagram illustrating the general interaction between a ventilator (a.k.a respirator) and the human respiratory system where increasing the air pressure in the lungs facilitates the exchange of gas in the pulmonary alveolus ; a form of mechanical ventilation.
Image by Eleanor Lutz and Sarah Low
Modifications in Respiratory Functions
At rest, the respiratory system performs its functions at a constant, rhythmic pace, as regulated by the respiratory centers of the brain. At this pace, ventilation provides sufficient oxygen to all the tissues of the body. However, there are times that the respiratory system must alter the pace of its functions in order to accommodate the oxygen demands of the body.
Hyperpnea
Hyperpnea is an increased depth and rate of ventilation to meet an increase in oxygen demand as might be seen in exercise or disease, particularly diseases that target the respiratory or digestive tracts. This does not significantly alter blood oxygen or carbon dioxide levels, but merely increases the depth and rate of ventilation to meet the demand of the cells. In contrast, hyperventilationis an increased ventilation rate that is independent of the cellular oxygen needs and leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH.
Interestingly, exercise does not cause hyperpnea as one might think. Muscles that perform work during exercise do increase their demand for oxygen, stimulating an increase in ventilation. However, hyperpnea during exercise appears to occur before a drop in oxygen levels within the muscles can occur. Therefore, hyperpnea must be driven by other mechanisms, either instead of or in addition to a drop in oxygen levels. The exact mechanisms behind exercise hyperpnea are not well understood, and some hypotheses are somewhat controversial. However, in addition to low oxygen, high carbon dioxide, and low pH levels, there appears to be a complex interplay of factors related to the nervous system and the respiratory centers of the brain.
First, a conscious decision to partake in exercise, or another form of physical exertion, results in a psychological stimulus that may trigger the respiratory centers of the brain to increase ventilation. In addition, the respiratory centers of the brain may be stimulated through the activation of motor neurons that innervate muscle groups that are involved in the physical activity. Finally, physical exertion stimulates proprioceptors, which are receptors located within the muscles, joints, and tendons, which sense movement and stretching; proprioceptors thus create a stimulus that may also trigger the respiratory centers of the brain. These neural factors are consistent with the sudden increase in ventilation that is observed immediately as exercise begins. Because the respiratory centers are stimulated by psychological, motor neuron, and proprioceptor inputs throughout exercise, the fact that there is also a sudden decrease in ventilation immediately after the exercise ends when these neural stimuli cease, further supports the idea that they are involved in triggering the changes of ventilation.
High Altitude Effects
An increase in altitude results in a decrease in atmospheric pressure. Although the proportion of oxygen relative to gases in the atmosphere remains at 21 percent, its partial pressure decreases (Table). As a result, it is more difficult for a body to achieve the same level of oxygen saturation at high altitude than at low altitude, due to lower atmospheric pressure. In fact, hemoglobin saturation is lower at high altitudes compared to hemoglobin saturation at sea level. For example, hemoglobin saturation is about 67 percent at 19,000 feet above sea level, whereas it reaches about 98 percent at sea level.
Partial Pressure of Oxygen at Different Altitudes
Example location
Altitude (feet above sea level)
Atmospheric pressure (mm Hg)
Partial pressure of oxygen (mm Hg)
New York City, New York
0
760
159
Boulder, Colorado
5000
632
133
Aspen, Colorado
8000
565
118
Pike’s Peak, Colorado
14,000
447
94
Denali (Mt. McKinley), Alaska
20,000
350
73
Mt. Everest, Tibet
29,000
260
54
As you recall, partial pressure is extremely important in determining how much gas can cross the respiratory membrane and enter the blood of the pulmonary capillaries. A lower partial pressure of oxygen means that there is a smaller difference in partial pressures between the alveoli and the blood, so less oxygen crosses the respiratory membrane. As a result, fewer oxygen molecules are bound by hemoglobin. Despite this, the tissues of the body still receive a sufficient amount of oxygen during rest at high altitudes. This is due to two major mechanisms. First, the number of oxygen molecules that enter the tissue from the blood is nearly equal between sea level and high altitudes. At sea level, hemoglobin saturation is higher, but only a quarter of the oxygen molecules are actually released into the tissue. At high altitudes, a greater proportion of molecules of oxygen are released into the tissues. Secondly, at high altitudes, a greater amount of BPG is produced by erythrocytes, which enhances the dissociation of oxygen from hemoglobin. Physical exertion, such as skiing or hiking, can lead to altitude sickness due to the low amount of oxygen reserves in the blood at high altitudes. At sea level, there is a large amount of oxygen reserve in venous blood (even though venous blood is thought of as “deoxygenated”) from which the muscles can draw during physical exertion. Because the oxygen saturation is much lower at higher altitudes, this venous reserve is small, resulting in pathological symptoms of low blood oxygen levels. You may have heard that it is important to drink more water when traveling at higher altitudes than you are accustomed to. This is because your body will increase micturition (urination) at high altitudes to counteract the effects of lower oxygen levels. By removing fluids, blood plasma levels drop but not the total number of erythrocytes. In this way, the overall concentration of erythrocytes in the blood increases, which helps tissues obtain the oxygen they need.
Acute mountain sickness (AMS), or altitude sickness, is a condition that results from acute exposure to high altitudes due to a low partial pressure of oxygen at high altitudes. AMS typically can occur at 2400 meters (8000 feet) above sea level. AMS is a result of low blood oxygen levels, as the body has acute difficulty adjusting to the low partial pressure of oxygen. In serious cases, AMS can cause pulmonary or cerebral edema. Symptoms of AMS include nausea, vomiting, fatigue, lightheadedness, drowsiness, feeling disoriented, increased pulse, and nosebleeds. The only treatment for AMS is descending to a lower altitude; however, pharmacologic treatments and supplemental oxygen can improve symptoms. AMS can be prevented by slowly ascending to the desired altitude, allowing the body to acclimate, as well as maintaining proper hydration.
Acclimatization
Especially in situations where the ascent occurs too quickly, traveling to areas of high altitude can cause AMS. Acclimatization is the process of adjustment that the respiratory system makes due to chronic exposure to a high altitude. Over a period of time, the body adjusts to accommodate the lower partial pressure of oxygen. The low partial pressure of oxygen at high altitudes results in a lower oxygen saturation level of hemoglobin in the blood. In turn, the tissue levels of oxygen are also lower. As a result, the kidneys are stimulated to produce the hormone erythropoietin (EPO), which stimulates the production of erythrocytes, resulting in a greater number of circulating erythrocytes in an individual at a high altitude over a long period. With more red blood cells, there is more hemoglobin to help transport the available oxygen. Even though there is low saturation of each hemoglobin molecule, there will be more hemoglobin present, and therefore more oxygen in the blood. Over time, this allows the person to partake in physical exertion without developing AMS.
Chapter Review
Normally, the respiratory centers of the brain maintain a consistent, rhythmic breathing cycle. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high altitude results in a greater number of circulating erythrocytes. Hyperpnea, an increase in the rate and depth of ventilation, appears to be a function of three neural mechanisms that include a psychological stimulus, motor neuron activation of skeletal muscles, and the activation of proprioceptors in the muscles, joints, and tendons. As a result, hyperpnea related to exercise is initiated when exercise begins, as opposed to when tissue oxygen demand actually increases.
In contrast, acute exposure to a high altitude, particularly during times of physical exertion, does result in low blood and tissue levels of oxygen. This change is caused by a low partial pressure of oxygen in the air, because the atmospheric pressure at high altitudes is lower than the atmospheric pressure at sea level. This can lead to a condition called acute mountain sickness (AMS) with symptoms that include headaches, disorientation, fatigue, nausea, and lightheadedness. Over a long period of time, a person’s body will adjust to the high altitude, a process called acclimatization. During acclimatization, the low tissue levels of oxygen will cause the kidneys to produce greater amounts of the hormone erythropoietin, which stimulates the production of erythrocytes. Increased levels of circulating erythrocytes provide an increased amount of hemoglobin that helps supply an individual with more oxygen, preventing the symptoms of AMS.
Source: CNX OpenStax
Additional Materials (8)
Hyperventilation vs Hyperpnea
Hyperventilation is increased airflow in lung alveoli due to fast or deep breathing, while Hyperpnea describes breathing that is more rapid and deep.
Image by Scientific Animations, Inc.
Breathing Patterns (Abnormal and Irregular Respirations) | Respiratory Therapy Zone
Video by Respiratory Therapy Zone/YouTube
Mountain Climbers
The thin air at high elevations can strain the human respiratory system. (credit: “bortescristian”/flickr.com)
Image by CNX Openstax (credit: “bortescristian”/flickr.com)
Homeostasis
Blood sugar levels are controlled by a negative feedback loop. (credit: modification of work by Jon Sullivan)
Image by CNX Openstax (credit: modification of work by Jon Sullivan)
Homeostasis
Heat can be exchanged by four mechanisms: (a) radiation, (b) evaporation, (c) convection, or (d) conduction. (credit b: modification of work by “Kullez”/Flickr; credit c: modification of work by Chad Rosenthal; credit d: modification of work by “stacey.d”/Flickr)
Image by CNX Openstax
Homeostasis
The body is able to regulate temperature in response to signals from the nervous system.
Image by CNX Openstax
The Animal Body: Basic Form and Function
An arctic fox is a complex animal, well adapted to its environment. It changes coat color with the seasons, and has longer fur in winter to trap heat. (credit: modification of work by Keith Morehouse, USFWS)
Image by CNX Openstax (credit: modification of work by Keith Morehouse, USFWS)
Homeostasis, umbilical cord,
The birth of a human infant is the result of positive feedback.
Image by CNX Openstax
Hyperventilation vs Hyperpnea
Scientific Animations, Inc.
10:13
Breathing Patterns (Abnormal and Irregular Respirations) | Respiratory Therapy Zone
CNX Openstax (credit: modification of work by Jon Sullivan)
Homeostasis
CNX Openstax
Homeostasis
CNX Openstax
The Animal Body: Basic Form and Function
CNX Openstax (credit: modification of work by Keith Morehouse, USFWS)
Homeostasis, umbilical cord,
CNX Openstax
Embryonic Development of the Respiratory System
Fetus 9 Week Old (11 Weeks Gestational Age, 9 Weeks Fetal Age) Brain and Lung
Image by TheVisualMD
Fetus 9 Week Old (11 Weeks Gestational Age, 9 Weeks Fetal Age) Brain and Lung
Computer generated Image reconstructed from scanned human data. Actual size of fetus = 1.5 inches, 0.14 oz. This image provides a left-sided view of a 9-week-old fetus. The age is calculated from the day of fertilization. The image has been manipulated so that both internal and external structures are visible. In the head region, the brain is highlighted in pale yellow, and the left eye and left ear are indicated as pink rings. The left lung, shown beneath the arm, is marked in dark yellow. The liver, shown beneath the lung, is highlighted in pink. The dark pink tube-like structure alongside the fetus is the umbilical cord, which provides means of exchanging nutrients and wastes between mother and fetus. At this phase, the fetus begins to uncurl. Its head becomes more erect, back straightens, and the abdomen tucks in.
Image by TheVisualMD
Embryonic Development of the Respiratory System
Development of the respiratory system begins early in the fetus. It is a complex process that includes many structures, most of which arise from the endoderm. Towards the end of development, the fetus can be observed making breathing movements. Until birth, however, the mother provides all of the oxygen to the fetus as well as removes all of the fetal carbon dioxide via the placenta.
Time Line
The development of the respiratory system begins at about week 4 of gestation. By week 28, enough alveoli have matured that a baby born prematurely at this time can usually breathe on its own. The respiratory system, however, is not fully developed until early childhood, when a full complement of mature alveoli is present.
Weeks 4–7
Respiratory development in the embryo begins around week 4. Ectodermal tissue from the anterior head region invaginates posteriorly to form olfactory pits, which fuse with endodermal tissue of the developing pharynx. An olfactory pit is one of a pair of structures that will enlarge to become the nasal cavity. At about this same time, the lung bud forms. The lung bud is a dome-shaped structure composed of tissue that bulges from the foregut. The foregut is endoderm just inferior to the pharyngeal pouches. The laryngotracheal bud is a structure that forms from the longitudinal extension of the lung bud as development progresses. The portion of this structure nearest the pharynx becomes the trachea, whereas the distal end becomes more bulbous, forming bronchial buds. A bronchial bud is one of a pair of structures that will eventually become the bronchi and all other lower respiratory structures (image).
Development of the Lower Respiratory System
Weeks 7–16
Bronchial buds continue to branch as development progresses until all of the segmental bronchi have been formed. Beginning around week 13, the lumens of the bronchi begin to expand in diameter. By week 16, respiratory bronchioles form. The fetus now has all major lung structures involved in the airway.
Weeks 16–24
Once the respiratory bronchioles form, further development includes extensive vascularization, or the development of the blood vessels, as well as the formation of alveolar ducts and alveolar precursors. At about week 19, the respiratory bronchioles have formed. In addition, cells lining the respiratory structures begin to differentiate to form type I and type II pneumocytes. Once type II cells have differentiated, they begin to secrete small amounts of pulmonary surfactant. Around week 20, fetal breathing movements may begin.
Weeks 24–Term
Major growth and maturation of the respiratory system occurs from week 24 until term. More alveolar precursors develop, and larger amounts of pulmonary surfactant are produced. Surfactant levels are not generally adequate to create effective lung compliance until about the eighth month of pregnancy. The respiratory system continues to expand, and the surfaces that will form the respiratory membrane develop further. At this point, pulmonary capillaries have formed and continue to expand, creating a large surface area for gas exchange. The major milestone of respiratory development occurs at around week 28, when sufficient alveolar precursors have matured so that a baby born prematurely at this time can usually breathe on its own. However, alveoli continue to develop and mature into childhood. A full complement of functional alveoli does not appear until around 8 years of age.
Fetal “Breathing”
Although the function of fetal breathing movements is not entirely clear, they can be observed starting at 20–21 weeks of development. Fetal breathing movements involve muscle contractions that cause the inhalation of amniotic fluid and exhalation of the same fluid, with pulmonary surfactant and mucus. Fetal breathing movements are not continuous and may include periods of frequent movements and periods of no movements. Maternal factors can influence the frequency of breathing movements. For example, high blood glucose levels, called hyperglycemia, can boost the number of breathing movements. Conversely, low blood glucose levels, called hypoglycemia, can reduce the number of fetal breathing movements. Tobacco use is also known to lower fetal breathing rates. Fetal breathing may help tone the muscles in preparation for breathing movements once the fetus is born. It may also help the alveoli to form and mature. Fetal breathing movements are considered a sign of robust health.
Birth
Prior to birth, the lungs are filled with amniotic fluid, mucus, and surfactant. As the fetus is squeezed through the birth canal, the fetal thoracic cavity is compressed, expelling much of this fluid. Some fluid remains, however, but is rapidly absorbed by the body shortly after birth. The first inhalation occurs within 10 seconds after birth and not only serves as the first inspiration, but also acts to inflate the lungs. Pulmonary surfactant is critical for inflation to occur, as it reduces the surface tension of the alveoli. Preterm birth around 26 weeks frequently results in severe respiratory distress, although with current medical advancements, some babies may survive. Prior to 26 weeks, sufficient pulmonary surfactant is not produced, and the surfaces for gas exchange have not formed adequately; therefore, survival is low.
Review
The development of the respiratory system in the fetus begins at about 4 weeks and continues into childhood. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx. At about this same time, an protrusion of endodermal tissue extends anteriorly from the foregut, producing a lung bud, which continues to elongate until it forms the laryngotracheal bud. The proximal portion of this structure will mature into the trachea, whereas the bulbous end will branch to form two bronchial buds. These buds then branch repeatedly, so that at about week 16, all major airway structures are present. Development progresses after week 16 as respiratory bronchioles and alveolar ducts form, and extensive vascularization occurs. Alveolar type I cells also begin to take shape. Type II pulmonary cells develop and begin to produce small amounts of surfactant. As the fetus grows, the respiratory system continues to expand as more alveoli develop and more surfactant is produced. Beginning at about week 36 and lasting into childhood, alveolar precursors mature to become fully functional alveoli. At birth, compression of the thoracic cavity forces much of the fluid in the lungs to be expelled. The first inhalation inflates the lungs. Fetal breathing movements begin around week 20 or 21, and occur when contractions of the respiratory muscles cause the fetus to inhale and exhale amniotic fluid. These movements continue until birth and may help to tone the muscles in preparation for breathing after birth and are a sign of good health.
Source: CNX OpenStax
Additional Materials (11)
Embryology of the Lungs (Easy to Understand)
Video by Dr. Minass/YouTube
This browser does not support the video element.
10 Week Old Fetus Lung and Liver
Micro Magnetic Resonance Imaging based, stylized visualization of a 10-week fetus in utero. From this view, the developing liver can be seen as the large purple structure, the heart is the red structure in the middle of the torso and the developing nervous system is seen as the yellow nerve endings running along the back.
Video by TheVisualMD
This browser does not support the video element.
Fetus 8 Week Old Internal Organ
Week eight is a milestone in a baby's life. The Micro Magnetic Resonance Imaging based, visualization depicts a normal, but oversized looking liver in the thorax, a fairly defined lung with already distinguishable lobes, an already 4 chamber heart that beats now for about 4 weeks. By the end of this week the embryo has distinct human characteristics. Every organ and system is already in place. Developmental in the fetal period needs further differentiation of the organs and tissues and a rapid gain in size and weight.
Video by TheVisualMD
This browser does not support the video element.
10 Week Old Fetus with Developing Organ
Lateral view of a 10-week fetus in utero. The skin of the skin of the fetus is translucent to reveal the developing organs and systems. As the camera slowly zooms in, the skin fades away to reveal the developing liver, represented by the large purple mass and the developing heart, represented by the red structure above the liver. Also shown is the developing nevous system represented by the nerve endings along the back.
Video by TheVisualMD
This browser does not support the video element.
Fetus 8 Week Old Internal Anatomy
Week eight is a milestone in a baby's life. The Micro Magnetic Resonance Imaging based visualization reveals a normal, but oversized looking liver (purple) in the thorax, a fairly defined lung, an already 4 chamber heart that beats now for about 4 weeks. By the end of this week the embryo has distinct human characteristics. Every organ and system is already in place. Developmental in the fetal period needs further differentiation of the organs and tissues and a rapid gain in size and weight.
Video by TheVisualMD
This browser does not support the video element.
10 Week Old Fetus with Developing Organ
Micro Magnetic Resonance Imaging based, stylized visualization of a 10-week fetus in utero. The camera zooms in on the laterally placed fetus. As it does this the skin fades away to reveal the developing organ systems. From this view, the developing liver can be seen as the large purple structure, the heart is the red structure in the middle of the torso and the developing nervous system is seen as the yellow nerve endings running along the back.
Video by TheVisualMD
This browser does not support the video element.
Developing Body System of a Fetus
Camera zooms into a womb-like environment. Initially the fetus is seen within the environment, but is obscured by the surface of the womb-like bubble. The 6-month fetus is then revealed, and the camera rotates around it. As the camera rotates, the skin becomes more transparent. The various body systems are revealed in sequence. The clip ends by zooming out with the skin becoming more opaque.
Video by TheVisualMD
This browser does not support the video element.
Heart and Pulmonary System
An animation of a close up of the heart and pulmonary system. The camera rotates from right to left to show the heart, bronchi, pulmonary arteries, veins, within glass lungs, and a semi-transparent thorax and scapula. Since this animation was created in VG-Studiomax the background is black
Video by TheVisualMD
This browser does not support the video element.
From Cell to Whole Body
Animation showing an individual cell, camera zooms out as it then shows clusters of cells, then tissues then the whole body
Video by TheVisualMD
Embryology | Development of the Respiratory System
Video by Ninja Nerd/YouTube
Development of lungs- EASY NOTES ANATOMY
Video by MedgossipHD/YouTube
9:54
Embryology of the Lungs (Easy to Understand)
Dr. Minass/YouTube
0:13
10 Week Old Fetus Lung and Liver
TheVisualMD
0:27
Fetus 8 Week Old Internal Organ
TheVisualMD
0:22
10 Week Old Fetus with Developing Organ
TheVisualMD
0:27
Fetus 8 Week Old Internal Anatomy
TheVisualMD
0:12
10 Week Old Fetus with Developing Organ
TheVisualMD
1:14
Developing Body System of a Fetus
TheVisualMD
0:10
Heart and Pulmonary System
TheVisualMD
0:25
From Cell to Whole Body
TheVisualMD
45:11
Embryology | Development of the Respiratory System
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Respiratory System
The respiratory system is made up of organs and tissues that help you breathe. The main parts of this system are the airways, the lungs and linked blood vessels, and the muscles that enable breathing. Learn more.