A membrane of squamous EPITHELIAL CELLS, the mesothelial cells, covered by apical MICROVILLI that allow rapid absorption of fluid and particles in the PERITONEAL CAVITY. The peritoneum is divided into parietal and visceral components. The parietal peritoneum covers the inside of the ABDOMINAL WALL.
peritoneum - The tissue that lines the abdominal wall and covers most of the organs in the abdomen.
Image by TheVisualMD
Peritoneum
unlabeled peritoneal cavity sagittal section
Image by Sheldahl
unlabeled peritoneal cavity sagittal section
unlabeled peritoneal cavity sagittal section
Image by Sheldahl
Peritoneum
A membrane of squamous EPITHELIAL CELLS, the mesothelial cells, covered by apical MICROVILLI that allow rapid absorption of fluid and particles in the PERITONEAL CAVITY. The peritoneum is divided into parietal and visceral components. The parietal peritoneum covers the inside of the ABDOMINAL WALL. The visceral peritoneum covers the intraperitoneal organs. The double-layered peritoneum forms the MESENTERY that suspends these organs from the abdominal wall.
Source: National Center for Biotechnology Information (NCBI)
Additional Materials (8)
Peritoneum tutorial
Video by The Noted Anatomist/YouTube
Peritoneum - 3D Schematic Anatomy & Relations
Video by About Medicine/YouTube
Tracing the peritoneum in sections - simplified
Video by Human Anatomy Education/YouTube
4.3 what makes understanding the peritoneum so difficult?
Video by Centre for Innovation - Leiden University/YouTube
4.4 The relation of the peritoneum to the gut
Video by Centre for Innovation - Leiden University/YouTube
4.1 Introduction the peritoneum
Video by Centre for Innovation - Leiden University/YouTube
Peritoneal Relations (preview) - Human Anatomy | Kenhub
Video by Kenhub - Learn Human Anatomy/YouTube
Mesentery: organ and functions (preview) - Human Anatomy | Kenhub
Video by Kenhub - Learn Human Anatomy/YouTube
24:42
Peritoneum tutorial
The Noted Anatomist/YouTube
5:10
Peritoneum - 3D Schematic Anatomy & Relations
About Medicine/YouTube
32:05
Tracing the peritoneum in sections - simplified
Human Anatomy Education/YouTube
4:46
4.3 what makes understanding the peritoneum so difficult?
Centre for Innovation - Leiden University/YouTube
6:20
4.4 The relation of the peritoneum to the gut
Centre for Innovation - Leiden University/YouTube
2:53
4.1 Introduction the peritoneum
Centre for Innovation - Leiden University/YouTube
3:32
Peritoneal Relations (preview) - Human Anatomy | Kenhub
Kenhub - Learn Human Anatomy/YouTube
3:29
Mesentery: organ and functions (preview) - Human Anatomy | Kenhub
Kenhub - Learn Human Anatomy/YouTube
The Peritoneum
What are the types of peritoneal dialysis?
Image by TheVisualMD
What are the types of peritoneal dialysis?
Peritoneal dialysis uses the lining of the abdomen (peritoneum), which is rich in arteries and veins, as a filter. Dialysis fluid is placed into the abdominal cavity through a permanent access port in the abdomen. The fluid remains there long enough for all the wastes in the blood to be transferred to the dialysis fluid, which is then drained out of the abdomen.
Image by TheVisualMD
The Peritoneum
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs (image). The peritoneal cavity is the space bounded by the visceral and parietal peritoneal surfaces. A few milliliters of watery fluid act as a lubricant to minimize friction between the serosal surfaces of the peritoneum.
The visceral peritoneum includes multiple large folds that envelope various abdominal organs, holding them to the dorsal surface of the body wall. Within these folds are blood vessels, lymphatic vessels, and nerves that innervate the organs with which they are in contact, supplying their adjacent organs. The five major peritoneal folds are described in the Table below. Note that during fetal development, certain digestive structures, including the first portion of the small intestine (called the duodenum), the pancreas, and portions of the large intestine (the ascending and descending colon, and the rectum) remain completely or partially posterior to the peritoneum. Thus, the location of these organs is described as retroperitoneal .
The Five Major Peritoneal Folds
Fold
Description
Greater omentum
Apron-like structure that lies superficial to the small intestine and transverse colon; a site of fat deposition in people who are overweight
Falciform ligament
Anchors the liver to the anterior abdominal wall and inferior border of the diaphragm
Lesser omentum
Suspends the stomach from the inferior border of the liver; provides a pathway for structures connecting to the liver
Mesentery
Vertical band of tissue anterior to the lumbar vertebrae and anchoring all of the small intestine except the initial portion (the duodenum)
Mesocolon
Attaches two portions of the large intestine (the transverse and sigmoid colon) to the posterior abdominal wall
DISORDERS OF THE...
Digestive System: Peritonitis
Inflammation of the peritoneum is called peritonitis. Chemical peritonitis can develop any time the wall of the alimentary canal is breached, allowing the contents of the lumen entry into the peritoneal cavity. For example, when an ulcer perforates the stomach wall, gastric juices spill into the peritoneal cavity. Hemorrhagic peritonitis occurs after a ruptured tubal pregnancy or traumatic injury to the liver or spleen fills the peritoneal cavity with blood. Even more severe peritonitis is associated with bacterial infections seen with appendicitis, colonic diverticulitis, and pelvic inflammatory disease (infection of uterine tubes, usually by sexually transmitted bacteria). Peritonitis is life threatening and often results in emergency surgery to correct the underlying problem and intensive antibiotic therapy. When your great grandparents and even your parents were young, the mortality from peritonitis was high. Aggressive surgery, improvements in anesthesia safety, the advance of critical care expertise, and antibiotics have greatly improved the mortality rate from this condition. Even so, the mortality rate still ranges from 30 to 40 percent.
Source: CNX OpenStax
Additional Materials (13)
Peritoneal Cavity - Part 1 - Anatomy Tutorial
Video by AnatomyZone/YouTube
The Peritoneum
A cross-section of the abdomen shows the relationship between abdominal organs and the peritoneum (darker lines).
Image by CNX Openstax
General Distribution of the Peritoneum
Cross section through the abdomen showing the continuity of the parietal and visceral peritoneum through the mesentery and the principal muscles that contribute to the abdominal wall.
Image by Dennis M DePace, PhD/Wikimedia
Mesentery
Mesentery
Image by Anatomist90
Mesentery
Horizontal disposition of the peritoneum in the lower part of the abdomen.
Image by Henry Vandyke Carter
Mesentery - structure of the gut wall
The general structure of the gut wall
Image by Auawise at English Wikipedia
Peritoneal Cavity
Cross section of the Peritoneal Cavity
Image by Dr. Johannes Sobotta
Peritoneum - 3D Schematic Anatomy & Relations
Video by About Medicine/YouTube
Peritoneum tutorial
Video by The Noted Anatomist/YouTube
Tracing the peritoneum in sections - simplified
Video by Human Anatomy Education/YouTube
4.3 what makes understanding the peritoneum so difficult?
Video by Centre for Innovation - Leiden University/YouTube
4.4 The relation of the peritoneum to the gut
Video by Centre for Innovation - Leiden University/YouTube
4.1 Introduction the peritoneum
Video by Centre for Innovation - Leiden University/YouTube
8:28
Peritoneal Cavity - Part 1 - Anatomy Tutorial
AnatomyZone/YouTube
The Peritoneum
CNX Openstax
General Distribution of the Peritoneum
Dennis M DePace, PhD/Wikimedia
Mesentery
Anatomist90
Mesentery
Henry Vandyke Carter
Mesentery - structure of the gut wall
Auawise at English Wikipedia
Peritoneal Cavity
Dr. Johannes Sobotta
5:10
Peritoneum - 3D Schematic Anatomy & Relations
About Medicine/YouTube
24:42
Peritoneum tutorial
The Noted Anatomist/YouTube
32:05
Tracing the peritoneum in sections - simplified
Human Anatomy Education/YouTube
4:46
4.3 what makes understanding the peritoneum so difficult?
Centre for Innovation - Leiden University/YouTube
6:20
4.4 The relation of the peritoneum to the gut
Centre for Innovation - Leiden University/YouTube
2:53
4.1 Introduction the peritoneum
Centre for Innovation - Leiden University/YouTube
The Small and Large Intestines - Peritoneum
Attachments of the Parietal Peritoneum
Image by Dennis DePace, PhD
Attachments of the Parietal Peritoneum
Image by Dennis DePace, PhD
The Small and Large Intestines - Peritoneum
Structure
The coiled tube of the small intestine is subdivided into three regions. From proximal (at the stomach) to distal, these are the duodenum, jejunum, and ileum (Figure 23.18).
The shortest region is the 25.4-cm (10-in) duodenum, which begins at the pyloric sphincter. Just past the pyloric sphincter, it bends posteriorly behind the peritoneum, becoming retroperitoneal, and then makes a C-shaped curve around the head of the pancreas before ascending anteriorly again to return to the peritoneal cavity and join the jejunum. The duodenum can therefore be subdivided into four segments: the superior, descending, horizontal, and ascending duodenum.
Of particular interest is the hepatopancreatic ampulla (ampulla of Vater). Located in the duodenal wall, the ampulla marks the transition from the anterior portion of the alimentary canal to the mid-region, and is where the bile duct (through which bile passes from the liver) and the main pancreatic duct (through which pancreatic juice passes from the pancreas) join. This ampulla opens into the duodenum at a tiny volcano-shaped structure called the major duodenal papilla. The hepatopancreatic sphincter (sphincter of Oddi) regulates the flow of both bile and pancreatic juice from the ampulla into the duodenum.
Figure 23.18 Small Intestine The three regions of the small intestine are the duodenum, jejunum, and ileum.
The jejunum is about 0.9 meters (3 feet) long (in life) and runs from the duodenum to the ileum. Jejunum means “empty” in Latin and supposedly was so named by the ancient Greeks who noticed it was always empty at death. No clear demarcation exists between the jejunum and the final segment of the small intestine, the ileum.
The ileum is the longest part of the small intestine, measuring about 1.8 meters (6 feet) in length. It is thicker, more vascular, and has more developed mucosal folds than the jejunum. The ileum joins the cecum, the first portion of the large intestine, at the ileocecal sphincter (or valve). The jejunum and ileum are tethered to the posterior abdominal wall by the mesentery. The large intestine frames these three parts of the small intestine.
Parasympathetic nerve fibers from the vagus nerve and sympathetic nerve fibers from the thoracic splanchnic nerve provide extrinsic innervation to the small intestine. The superior mesenteric artery is its main arterial supply. Veins run parallel to the arteries and drain into the superior mesenteric vein. Nutrient-rich blood from the small intestine is then carried to the liver via the hepatic portal vein.
Histology
The wall of the small intestine is composed of the same four layers typically present in the alimentary system. However, three features of the mucosa and submucosa are unique. These features, which increase the absorptive surface area of the small intestine more than 600-fold, include circular folds, villi, and microvilli (Figure 23.19). These adaptations are most abundant in the proximal two-thirds of the small intestine, where the majority of absorption occurs.
The cecum blends seamlessly with the colon. Upon entering the colon, the food residue first travels up the ascending colon on the right side of the abdomen. At the inferior surface of the liver, the colon bends to form the right colic flexure (hepatic flexure) and becomes the transverse colon. The region defined as hindgut begins with the last third of the transverse colon and continues on. Food residue passing through the transverse colon travels across to the left side of the abdomen, where the colon angles sharply immediately inferior to the spleen, at the left colic flexure (splenic flexure). From there, food residue passes through the descending colon, which runs down the left side of the posterior abdominal wall. After entering the pelvis inferiorly, it becomes the s-shaped sigmoid colon, which extends medially to the midline (Figure 23.21). The ascending and descending colon, and the rectum (discussed next) are located in the retroperitoneum. The transverse and sigmoid colon are tethered to the posterior abdominal wall by the mesocolon.
Figure 23.21 Large Intestine The large intestine includes the cecum, colon, and rectum.
Anatomy
Three features are unique to the large intestine: teniae coli, haustra, and epiploic appendages (Figure 23.23). The teniae coli are three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. Tonic contractions of the teniae coli bunch up the colon into a succession of pouches called haustra (singular = haustrum), which are responsible for the wrinkled appearance of the colon. Attached to the teniae coli are small, fat-filled sacs of visceral peritoneum called epiploic appendages. The purpose of these is unknown. Although the rectum and anal canal have neither teniae coli nor haustra, they do have well-developed layers of muscularis that create the strong contractions needed for defecation.
Figure 23.23 Teniae Coli, Haustra, and Epiploic Appendages
The stratified squamous epithelial mucosa of the anal canal connects to the skin on the outside of the anus. This mucosa varies considerably from that of the rest of the colon to accommodate the high level of abrasion as feces pass through. The anal canal’s mucous membrane is organized into longitudinal folds, each called an anal column, which house a grid of arteries and veins. Two superficial venous plexuses are found in the anal canal: one within the anal columns and one at the anus.
Depressions between the anal columns, each called an anal sinus, secrete mucus that facilitates defecation. The pectinate line (or dentate line) is a horizontal, jagged band that runs circumferentially just below the level of the anal sinuses, and represents the junction between the hindgut and external skin. The mucosa above this line is fairly insensitive, whereas the area below is very sensitive. The resulting difference in pain threshold is due to the fact that the upper region is innervated by visceral sensory fibers, and the lower region is innervated by somatic sensory fibers.
Source: CNX OpenStax
Additional Materials (2)
unlabeled peritoneal cavity sagittal section
unlabeled peritoneal cavity sagittal section
Image by Sheldahl
General Distribution of the Peritoneum
Cross section through the abdomen showing the continuity of the parietal and visceral peritoneum through the mesentery and the principal muscles that contribute to the abdominal wall.
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Peritoneum
A membrane of squamous EPITHELIAL CELLS, the mesothelial cells, covered by apical MICROVILLI that allow rapid absorption of fluid and particles in the PERITONEAL CAVITY. The peritoneum is divided into parietal and visceral components. The parietal peritoneum covers the inside of the ABDOMINAL WALL.