The esophagus is a muscular tube that carries food and liquids from your throat to your stomach. Muscles in your esophagus propel food downward. Learn more about the esophagus and how it works.
Esophagus and Digestive System
Image by TheVisualMD
Esophagus
Normal Esophagus
Image by Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities
Normal Esophagus
Normal Esophagus
Image by Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities
Esophagus
The esophagus is a muscular tube that connects the pharynx to the stomach. It is approximately 25.4 cm (10 in) in length, located posterior to the trachea, and remains in a collapsed form when not engaged in swallowing. As you can see in image below, the esophagus runs a mainly straight route through the mediastinum of the thorax. To enter the abdomen, the esophagus penetrates the diaphragm through an opening called the esophageal hiatus.
Passage of Food through the Esophagus
The upper esophageal sphincter, which is continuous with the inferior pharyngeal constrictor, controls the movement of food from the pharynx into the esophagus. The upper two-thirds of the esophagus consists of both smooth and skeletal muscle fibers, with the latter fading out in the bottom third of the esophagus. Rhythmic waves of peristalsis, which begin in the upper esophagus, propel the bolus of food toward the stomach. Meanwhile, secretions from the esophageal mucosa lubricate the esophagus and food. Food passes from the esophagus into the stomach at the lower esophageal sphincter (also called the gastroesophageal or cardiac sphincter). Recall that sphincters are muscles that surround tubes and serve as valves, closing the tube when the sphincters contract and opening it when they relax. The lower esophageal sphincter relaxes to let food pass into the stomach, and then contracts to prevent stomach acids from backing up into the esophagus. Surrounding this sphincter is the muscular diaphragm, which helps close off the sphincter when no food is being swallowed. When the lower esophageal sphincter does not completely close, the stomach’s contents can reflux (that is, back up into the esophagus), causing heartburn or gastroesophageal reflux disease (GERD).
Esophagus
The upper esophageal sphincter controls the movement of food from the pharynx to the esophagus. The lower esophageal sphincter controls the movement of food from the esophagus to the stomach.
Histology of the Esophagus
The mucosa of the esophagus is made up of an epithelial lining that contains non-keratinized, stratified squamous epithelium, with a layer of basal and parabasal cells. This epithelium protects against erosion from food particles. The mucosa’s lamina propria contains mucus-secreting glands. The muscularis layer changes according to location: In the upper third of the esophagus, the muscularis is skeletal muscle. In the middle third, it is both skeletal and smooth muscle. In the lower third, it is smooth muscle. As mentioned previously, the most superficial layer of the esophagus is called the adventitia, not the serosa. In contrast to the stomach and intestines, the loose connective tissue of the adventitia is not covered by a fold of visceral peritoneum. The digestive functions of the esophagus are identified in image.
Digestive Functions of the Esophagus
Action
Outcome
Upper esophageal sphincter relaxation
Allows the bolus to move from the laryngopharynx to the esophagus
Peristalsis
Propels the bolus through the esophagus
Lower esophageal sphincter relaxation
Allows the bolus to move from the esophagus into the stomach and prevents chime from entering the esophagus
Mucus secretion
Lubricates the esophagus, allowing easy passage of the bolus
Source: CNX OpenStax
Additional Materials (10)
Digestive Tract Anatomy
Anatomy of the digestive tract. The digestive tract is made up of organs that food and liquids travel through when they are swallowed, digested, absorbed, and leave the body as feces. These organs include the mouth, pharynx (throat), esophagus, stomach, small intestine, large intestine, rectum, and anus.
Drawing of the digestive system with esophagus, stomach, and duodenum highlighted
NIDDK Image Library
Esophagus and Digestive System
TheVisualMD
5:34
Esophagus | Gastrointestinal system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
4:07
Esophagus Definition, Function and Structure - Human Anatomy | Kenhub
Kenhub - Learn Human Anatomy/YouTube
3:37
Human Body for Kids/Esophagus Song for Kids/Human Body Systems
Kids Learning Tube/YouTube
15:11
The Oesophagus (Esophagus) - Clinical Anatomy
Armando Hasudungan/YouTube
Digestive System
Esophagus
Image by Cenveo
Esophagus
The esophagus is a collapsible tube located posterior to the trachea. This muscular tube is about 10 inches long. The esophagus runs a mainly straight route through the mediastinum of the thorax. To enter the abdomen, the esophagus penetrates the diaphragm through an opening called the esophageal hiatus. At the cardiac orifice, the esophagus joins with the stomach. Surrounding this orifice is the lower esophageal sphincter (also called the gastroesophageal or cardiac sphincter). Remember that sphincters are circular muscles that surround tubes and serve as valves, closing the tube when the sphincters contract and opening it when they relax. The lower esophageal sphincter relaxes to let food pass into the stomach, then contracts to prevent stomach contents from backing up into the esophagus. Surrounding this sphincter is the muscular diaphragm, which helps close off the sphincter when no food is being swallowed. When the lower esophageal sphincter does not completely close, some of the stomach contents can reflux (i.e., back up into the esophagus), causing heartburn or gastroesophageal reflux disease (GERD).
Image by Cenveo
Esophagus and Digestive System
The Human Digestive System
The process of digestion begins in the mouth with the intake of food (Figure 16.4). The teeth play an important role in masticating (chewing) or physically breaking food into smaller particles. The enzymes present in saliva also begin to chemically break down food. The food is then swallowed and enters the esophagus—a long tube that connects the mouth to the stomach. Using peristalsis, or wave-like smooth-muscle contractions, the muscles of the esophagus push the food toward the stomach. The stomach contents are extremely acidic, with a pH between 1.5 and 2.5. This acidity kills microorganisms, breaks down food tissues, and activates digestive enzymes. Further breakdown of food takes place in the small intestine where bile produced by the liver, and enzymes produced by the small intestine and the pancreas, continue the process of digestion. The smaller molecules are absorbed into the blood stream through the epithelial cells lining the walls of the small intestine. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces; it is stored until it is excreted through the anus.
Figure 16.4 The components of the human digestive system are shown.
Digestive Processes
The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.
The first of these processes, ingestion, refers to the entry of food into the alimentary canal through the mouth. There, the food is chewed and mixed with saliva, which contains enzymes that begin breaking down the carbohydrates in the food plus some lipid digestion via lingual lipase. Chewing increases the surface area of the food and allows an appropriately sized bolus to be produced.
Food leaves the mouth when the tongue and pharyngeal muscles propel it into the esophagus. This act of swallowing, the last voluntary act until defecation, is an example of propulsion, which refers to the movement of food through the digestive tract. It includes both the voluntary process of swallowing and the involuntary process of peristalsis. Peristalsis consists of sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along (Figure 23.5). These waves also play a role in mixing food with digestive juices. Peristalsis is so powerful that foods and liquids you swallow enter your stomach even if you are standing on your head.
Figure 23.5 Peristalsis Peristalsis moves food through the digestive tract with alternating waves of muscle contraction and relaxation.
Digestion includes both mechanical and chemical processes. Mechanical digestion is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva. Although there may be a tendency to think that mechanical digestion is limited to the first steps of the digestive process, it occurs after the food leaves the mouth, as well. The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digestive juices, creating an acidic “soup” called chyme. Segmentation, which occurs mainly in the small intestine, consists of localized contractions of circular muscle of the muscularis layer of the alimentary canal. These contractions isolate small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents. By moving food back and forth in the intestinal lumen, segmentation mixes food with digestive juices and facilitates absorption.
In chemical digestion, starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks (for example, proteins into separate amino acids). These secretions vary in composition, but typically contain water, various enzymes, acids, and salts. The process is completed in the small intestine.
Food that has been broken down is of no value to the body unless it enters the bloodstream and its nutrients are put to work. This occurs through the process of absorption, which takes place primarily within the small intestine. There, most nutrients are absorbed from the lumen of the alimentary canal into the bloodstream through the epithelial cells that make up the mucosa. Lipids are absorbed into lacteals and are transported via the lymphatic vessels to the bloodstream (the subclavian veins near the heart). The details of these processes will be discussed later.
In defecation, the final step in digestion, undigested materials are removed from the body as feces.
In some cases, a single organ is in charge of a digestive process. For example, ingestion occurs only in the mouth and defecation only in the anus. However, most digestive processes involve the interaction of several organs and occur gradually as food moves through the alimentary canal (Figure 23.6).
Figure 23.6 Digestive Processes The digestive processes are ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
The esophagus is a tubular organ that connects the mouth to the stomach. The chewed and softened food passes through the esophagus after being swallowed. The smooth muscles of the esophagus undergo peristalsis that pushes the food toward the stomach. The peristaltic wave is unidirectional—it moves food from the mouth the stomach, and reverse movement is not possible, except in the case of the vomit reflex. The peristaltic movement of the esophagus is an involuntary reflex; it takes place in response to the act of swallowing.
Ring-like muscles called sphincters form valves in the digestive system. The gastro-esophageal sphincter (or cardiac sphincter) is located at the stomach end of the esophagus. In response to swallowing and the pressure exerted by the bolus of food, this sphincter opens, and the bolus enters the stomach. When there is no swallowing action, this sphincter is shut and prevents the contents of the stomach from traveling up the esophagus. Acid reflux or “heartburn” occurs when the acidic digestive juices escape into the esophagus.
Figure 16.5 (a) Digestion of food begins in the mouth. (b) Food is masticated by teeth and moistened by saliva secreted from the salivary glands. Enzymes in the saliva begin to digest starches and fats. With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing. (credit: modification of work by Mariana Ruiz Villareal)
Source: CNX OpenStax
Additional Materials (9)
Esophageal disease
Esophagus, Stomach, Small Intestine
Image by National Cancer Institute
Drawing of the digestive tract within an outline of the human body. The mouth, esophagus, stomach, small intestine, large intestine, colon, rectum, and anus are labeled
Organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus.
Image by NIDDK Image Library
Esophagus
stylized cross section of esophagus and layers of esophagus
Image by Boumphreyfr
Esophagus
Esophagus
Image by training.seer.cancer.gov
Drawing of the esophagus with a portion of the esophagus emerging from the windpipe
One form of esophageal atresia.
Image by NIDDK Image Library
Top: drawing of a cross section of a normal esophagus. Bottom: drawing of a cross section of an esophagus with webs
Normal esophagus and esophagus with webs.
Image by NIDDK Image Library
An animated image to show Peristalsis
An animated image to show Peristalsis
Image by Auawise
Digestive Systems
The esophagus transfers food from the mouth to the stomach through peristaltic movements.
Image by CNX Openstax
Introduction to the Digestive System Part 2 - Oesophagus and Stomach - 3D Anatomy Tutorial
Video by AnatomyZone/YouTube
Esophageal disease
National Cancer Institute
Drawing of the digestive tract within an outline of the human body. The mouth, esophagus, stomach, small intestine, large intestine, colon, rectum, and anus are labeled
NIDDK Image Library
Esophagus
Boumphreyfr
Esophagus
training.seer.cancer.gov
Drawing of the esophagus with a portion of the esophagus emerging from the windpipe
NIDDK Image Library
Top: drawing of a cross section of a normal esophagus. Bottom: drawing of a cross section of an esophagus with webs
NIDDK Image Library
An animated image to show Peristalsis
Auawise
Digestive Systems
CNX Openstax
5:59
Introduction to the Digestive System Part 2 - Oesophagus and Stomach - 3D Anatomy Tutorial
AnatomyZone/YouTube
Pharynx and Esophagus
Anatomy of Upper Digestive Tract Involved in Swallowing
Image by TheVisualMD
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
Pharynx & Esophagus
Pharynx
Food is forced into the pharynx by the tongue. When food reaches the opening, sensory receptors around the fauces respond and initiate an involuntary swallowing reflex. This reflex action has several parts. The uvula is elevated to prevent food from entering the nasopharynx. The epiglottis drops downward to prevent food from entering the larynx and trachea in order to direct the food into the esophagus. Peristaltic movements propel the food from the pharynx into the esophagus.
Esophagus
The esophagus is a collapsible muscular tube that serves as a passageway between the pharynx and stomach. As it descends, it is posterior to the trachea and anterior to the vertebral column. It passes through an opening in the diaphragm, called the esophageal hiatus, and then empties into the stomach. The mucosa has glands that secrete mucus to keep the lining moist and well lubricated to ease the passage of food. Upper and lower esophageal sphincters control the movement of food into and out of the esophagus. The lower esophageal sphincter is sometimes called the cardiac sphincter and resides at the esophagogastric junction.
Source: National Cancer Institute (NCI)
Additional Materials (4)
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. The pharynx has three connected sections. The nasopharynx lies at the back of the nasal cavity. The oropharynx runs from the back of the oral cavity down to the epiglottis (a flap of tissue that closes off the larynx during swallowing). The laryngopharynx extends from the epiglottis to the 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. The pharyngeal muscles can constrict the passages of the pharynx and can close off the different apertures in ways necessary for swallowing, speaking, singing, or blowing. Obstructive sleep apnea (OSA), the temporary stoppage of breathing during sleep, is due to airflow obstruction caused by collapse of the pharynx. Temporary episodes of sleep apnea are not unusual, even in healthy individuals. They may be the result of an upper respiratory infection that causes nasal congestion, tonsillitis, or swelling of the throat due, for example, to infectious mononucleosis. However, some individuals suffer from severe, chronic OSA, and may go for years without knowing they have the disorder.
Image by TheVisualMD
Esophagus | Gastrointestinal system physiology | NCLEX-RN | Khan Academy
Video by khanacademymedicine/YouTube
Esophagus
The upper esophageal sphincter controls the movement of food from the pharynx to the esophagus. The lower esophageal sphincter controls the movement of food from the esophagus to the stomach.
Image by CNX Openstax
Digestive Systems
Digestion of food begins in the (a) oral cavity. Food is masticated by teeth and moistened by saliva secreted from the (b) salivary glands. Enzymes in the saliva begin to digest starches and fats. With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing. (credit: modification of work by the National Cancer Institute)
Image by CNX Openstax
Head with Pharynx cross section
TheVisualMD
5:34
Esophagus | Gastrointestinal system physiology | NCLEX-RN | Khan Academy
khanacademymedicine/YouTube
Esophagus
CNX Openstax
Digestive Systems
CNX Openstax
Passage of Food Through the Esophagus
Upper Digestive Tract
Image by TheVisualMD
Upper Digestive Tract
3D visualization reconstructed from scanned human data of the structures involved in the action of swallowing. A bolus of food is depicted in the esophagus. The epiglottis bent down to cover the windpipe to allow for the passage of the bolus. 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
Passage of Food Through the Esophagus
The Esophagus
The esophagus is a muscular tube that connects the pharynx to the stomach. It is approximately 25.4 cm (10 in) in length, located posterior to the trachea, and remains in a collapsed form when not engaged in swallowing. As you can see in Figure 23.13, the esophagus runs a mainly straight route through the mediastinum of the thorax. To enter the abdomen, the esophagus penetrates the diaphragm through an opening called the esophageal hiatus.
Passage of Food through the Esophagus
The upper esophageal sphincter, which is continuous with the inferior pharyngeal constrictor, controls the movement of food from the pharynx into the esophagus. The upper two-thirds of the esophagus consists of both smooth and skeletal muscle fibers, with the latter fading out in the bottom third of the esophagus. Rhythmic waves of peristalsis, which begin in the upper esophagus, propel the bolus of food toward the stomach. Meanwhile, secretions from the esophageal mucosa lubricate the esophagus and food. Food passes from the esophagus into the stomach at the lower esophageal sphincter (also called the gastroesophageal or cardiac sphincter). Recall that sphincters are muscles that surround tubes and serve as valves, closing the tube when the sphincters contract and opening it when they relax. The lower esophageal sphincter relaxes to let food pass into the stomach, and then contracts to prevent stomach acids from backing up into the esophagus. Surrounding this sphincter is the muscular diaphragm, which helps close off the sphincter when no food is being swallowed. When the lower esophageal sphincter does not completely close, the stomach’s contents can reflux (that is, back up into the esophagus), causing heartburn or gastroesophageal reflux disease (GERD).
Histology of the Esophagus
The mucosa of the esophagus is made up of an epithelial lining that contains non-keratinized, stratified squamous epithelium, with a layer of basal and parabasal cells. This epithelium protects against erosion from food particles. The mucosa’s lamina propria contains mucus-secreting glands. The muscularis layer changes according to location: In the upper third of the esophagus, the muscularis is skeletal muscle. In the middle third, it is both skeletal and smooth muscle. In the lower third, it is smooth muscle. As mentioned previously, the most superficial layer of the esophagus is called the adventitia, not the serosa. In contrast to the stomach and intestines, the loose connective tissue of the adventitia is not covered by a fold of visceral peritoneum. The digestive functions of the esophagus are identified in Table 23.5.
Digestive Functions of the Esophagus
Action
Outcome
Upper esophageal sphincter relaxation
Allows the bolus to move from the laryngopharynx to the esophagus
Peristalsis
Propels the bolus through the esophagus
Lower esophageal sphincter relaxation
Allows the bolus to move from the esophagus into the stomach and prevents chyme from entering the esophagus
Mucus secretion
Lubricates the esophagus, allowing easy passage of the bolus
Table 23.5
Deglutition
Deglutition is another word for swallowing—the movement of food from the mouth to the stomach. The entire process takes about 4 to 8 seconds for solid or semisolid food, and about 1 second for very soft food and liquids. Although this sounds quick and effortless, deglutition is, in fact, a complex process that involves both the skeletal muscle of the tongue and the muscles of the pharynx and esophagus. It is aided by the presence of mucus and saliva. There are three stages in deglutition: the voluntary phase, the pharyngeal phase, and the esophageal phase (Figure 23.14). The autonomic nervous system controls the latter two phases.
Figure 23.14 Deglutition Deglutition includes the voluntary phase and two involuntary phases: the pharyngeal phase and the esophageal phase.
The Voluntary Phase
The voluntary phase of deglutition (also known as the oral or buccal phase) is so called because you can control when you swallow food. In this phase, chewing has been completed and swallowing is set in motion. The tongue moves upward and backward against the palate, pushing the bolus to the back of the oral cavity and into the oropharynx. Other muscles keep the mouth closed and prevent food from falling out. At this point, the two involuntary phases of swallowing begin.
The Pharyngeal Phase
In the pharyngeal phase, stimulation of receptors in the oropharynx sends impulses to the deglutition center (a collection of neurons that controls swallowing) in the medulla oblongata. Impulses are then sent back to the uvula and soft palate, causing them to move upward and close off the nasopharynx. The laryngeal muscles also constrict to prevent aspiration of food into the trachea. At this point, deglutition apnea takes place, which means that breathing ceases for a very brief time. Contractions of the pharyngeal constrictor muscles move the bolus through the oropharynx and laryngopharynx. Relaxation of the upper esophageal sphincter then allows food to enter the esophagus.
The Esophageal Phase
The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of peristalsis. As in the previous phase, the complex neuromuscular actions are controlled by the medulla oblongata. Peristalsis propels the bolus through the esophagus and toward the stomach. The circular muscle layer of the muscularis contracts, pinching the esophageal wall and forcing the bolus forward. At the same time, the longitudinal muscle layer of the muscularis also contracts, shortening this area and pushing out its walls to receive the bolus. In this way, a series of contractions keeps moving food toward the stomach. When the bolus nears the stomach, distention of the esophagus initiates a short reflex relaxation of the lower esophageal sphincter that allows the bolus to pass into the stomach. During the esophageal phase, esophageal glands secrete mucus that lubricates the bolus and minimizes friction.
Additional Materials (13)
HealthyEsophagus and GERD
Gastroesophageal Reflux Disease (GERD) : A figure with visible gastrointestinal tract is shown to compare a healthy esophagus and an inflamed esophagus due to erosion by stomach acid in a condition known as gastroesophageal reflux disease (GERD). GERD is a disorder in which the sphincter muscle at the base of the esophagus relaxes at the wrong time, causing stomach acid to flow backwards into the esophagus. The acid irritates and inflames the lining of the esophagus, causing a burning sensation. Changes in diet and lifestyle can help reduce or eliminate symptoms of GERD and also lower the risk of developing the disease in the first place.
Image by TheVisualMD
Digestive system - Peristalsis
Peristalsis
Image by Laboratoires Servier
/Wikimedia
GERD
A figure with visible gastrointestinal tract is shown to compare a healthy esophagus and an inflamed esophagus due to erosion by stomach acid in a condition known as gastroesophageal reflux disease (GERD). GERD is a disorder in which the sphincter muscle at the base of the esophagus relaxes at the wrong time, causing stomach acid to flow backwards into the esophagus. The acid irritates and inflames the lining of the esophagus, causing a burning sensation. Changes in diet and lifestyle can help reduce or eliminate symptoms of GERD and also lower the risk of developing the disease in the first place.
Image by TheVisualMD
Esophagus
Scheme of digestive tract, with espohagus marked.
Image by Olek Remesz (wiki-pl: Orem, commons: Orem)
An animated image to show Peristalsis
An animated image to show Peristalsis
Image by Auawise
Cross section of a trachea and esophagus
Cross-sectional diagram of a trachea and esophagus
Image by PBrieux/Wikimedia
How peristalsis works
how peristalsis works.
Image by OpenStax College/Wikimedia
Male Torso with Visible 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.
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Esophagus
The esophagus is a muscular tube that carries food and liquids from your throat to your stomach. Muscles in your esophagus propel food downward. Learn more about the esophagus and how it works.