Peritoneum and Omentum Notes PDF

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Summary

Gastrointestinal system: Peritoneum and Omentum anatomy notes...

Description

Peritoneum    

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The peritoneum is a continuous, glistening and slippery transparent serous membrane which lines the abdominopelvic cavity and invests the viscera The peritoneum consist of 2 continuous layers- the parietal peritoneum (lines the internal surface of the abdominopelvic wall) and the visceral peritoneum (invests viscera such as the stomach and intestines) Both layers of peritoneum consist of mesothelium- a layer of simple squamous epithelial cells The parietal peritoneum is served by the same blood and lymphatic vasculature and the same somatic nerve supply with the region of the wall it overlies o Like the overlying skin, the peritoneum lining the internal body wall is sensitive to pressure, pain, heat, cold and laceration o Pain from the parietal peritoneum is generally well localized, except for the inferior surface of the central part of the diaphragm (irritation here if often referred to the C3-C5 dermatomes over the shoulder) The visceral peritoneum and the organs it covers are served by the same blood and lymphatic vasculature and visceral nerve supply o The visceral peritoneum is insensitive to touch, heat, cold and laceration- it is stimulated primarily by stretching and chemical irritation o The pain produced is poorly localized, being referred to the dermatomes of the spinal ganglia providing the sensory fibers, particularly to midline portions of these dermatomes o Pain from the foregut experienced in the epigastric region, pain from the midgut experienced in the umbilical region and pain from the hindgut in the pelvic region Intraperitoneal means that the organs have invaginated into the closed sac e.g. like pressing your fist into an inflated balloon Extraperitoneal/retroperitoneal/subperitoneal organs are also outside the peritoneal cavity and are only partially covered with peritoneum e.g. the kidneys are only covered by the peritoneum on their anterior walls The peritoneal cavity is within the abdominal cavity and continues inferiorly into the pelvic cavity o Contains peritoneal fluid which is composed of water, electrolytes and other substances derived from interstitial fluid in adjacent tissues o Lubricates the peritoneal surfaces enabling the viscera to move over each other without friction and allowing the movements of digestion o In addition to lubrication, the peritoneal fluid contains leukocytes and antibodies that resist infection o Lymph vessels particularly on the unceasingly active diaphragm absorbs peritoneal fluid o The cavity is completely closed in males but in females, there is a communication pathway to the exterior of the body through the uterine tubes, uterine cavity and vagina (increases likelihood of infection)

Peritoneal Formations 

The peritoneum has a complex shape: o Houses a great length of gut’ o Extensive continuities are required between the parietal and visceral peritoneum to convey the necessary neurovascular structures from the body wall to the viscera o The visceral and parietal peritoneum lining the cavity within it have a much greater surface area than the body’s outside surface

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Mesentery is a double layer of peritoneum- continuity of the visceral and parietal peritoneum- provides a means for neurovascular communication between the organ and body wall o Made up of a core of connective tissue, containing blood, lymph vessels, nerves, lymph nodes and fat An omentum is a double layered extension or fold of peritoneum that passes from the stomach and proximal part of the duodenum to adjacent organs in the abdominal cavity o The greater omentum is a prominent peritoneal fold that hangs down from the greater curvature of the stomach and the proximal part of the duodenum and folds back and attaches to the anterior surface of the transverse colon and it’s mesentery  The greater omentum is large and fat laden, and prevents the visceral peritoneum from adhering to the parietal peritoneum  It has considerable motility and moves around the peritoneal cavity with peristaltic movements of the viscera  It often forms adhesions adjacent to an inflamed appendix, walling it off and protecting other viscera from it  Common to find the greater omentum displaced during surgery o The lesser omentum connects the lesser curvature of the stomach and the proximal part of the duodenum to the liver A peritoneal ligament consists of a double layer of peritoneum that connects an organ with another organ or to the abdominal wall A peritoneal fold is a reflection of peritoneum that is raised from the body wall by underlying blood vessels, ducts and obliterated fetal vessels A peritoneal recess is a pouch of peritoneum that is formed by a peritoneal fold e.g. the inferior recess of the omental bursa between layers of the greater omentum and the supravesical and umbilical fossae between the umbilical folds The peritoneal cavity is divided into the greater and lesser peritoneal sacs with the greater sac being the main and larger part A surgical incision through the anterolateral abdominal wall enters the greater sac The omental bursa is the lesser sac and lies posterior to the stomach and the lesser omentum The transverse mescolon divides the abdominal cavity into supracolic (stomach, liver and spleen) and infracolic (small intestine, ascending and descending colon) compartments The infracolic compartment lies posterior to the greater omentum and is divided into right and left infracolic spaces by the mesentery of the small intestine Free communication between the supra and infracolic compartment occurs via the paracolic gutters (grooves between the lateral aspect of the ascending and descending colon and the posterior abdominal wall) The omental bursa (lesser sac) lies posterior to the stomach and lesser omentum and adjacent structures o Superior recess is limited superiorly by the diaphragm and the posterior layers of the coronary ligament of the liver o Inferior recess between the superior parts of the layers of greater omentum o The omental bursa permits free movement of the stomach o Most of the inferior recess becomes sealed off after adhesion of the anterior and posterior layers of the greater omentum o The omental bursa communicates with the greater peritoneal sac through the omental foramen situated posterior to the free edge of the lesser omentum

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The foramen of Winslow is the passage of communication between the greater and lesser sac- borders: o Anterior- free border of the lesser omentum o Posterior- peritoneum covering the inferior vena cava o Superior- peritoneum covering the caudate lobe of the liver o Inferior- the peritoneum covering the commencement of the duodenum and hepatic artery o Left lateral- gastrosplenic ligament and lineorenal ligament...