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What is the peritoneum?

A single layer of squamous epithelium called mesothelium which is derived from the mesodermal layer of the developing embryo. It invests most of the digestive and reproductive organs, as well as the walls of the abdominal and pelvic cavities.


What is the peritoneal cavity?

The potential space occupied only by fluid that lies between the parietal and visceral peritoneal layers. It occupies the full extent of the abdominal and pelvic cavities


Is the peritoneal cavity open or closed?

Closed in males: no natural communication between peritoneal cavity and outside
Ope in females: Opening of uterine tube is not covered by peritoneum! potential place for spread of infections


What are the two layers of peritoneum?

Parietal layer - lines abdominal and pelvic walls
Visceral layer - invests the viscera of the abdominal and pelvic organs


What is a mesentery? Give an example

A double layer of peritoneum attached to a body wall that encloses part or all of an organ and its supply of vessels (arteries, veins, lymphatics) and nerves. An organ suspended by mesentery will be mobile.

Example: Transverse mesocolon


What is an omentum? Give an example

A double-layered fold of peritoneum passing from the stomach and first part of the duodenum to another abdominal organ.

Examples: Greater and lesser omentum


What is the greater omentum?

Omentum attaching to greater curvature of the stomach + first part of duodenum and inserting on transverse colon


What is the lesser omentum and its two parts?

Omentum attached to lesser curvature of stomach and first part of duodenum and inserting on visceral /inferior surface of the liver.
Hepatoduodenal ligament - connects liver to first part of duodenum
Hepatogastric ligament - connects liver to lesser curvature of the stomach


What is a peritoneal ligament? Give an example

A double-layered extension of the peritoneum that connects an organ with any adjacent organ or body wall. An omentum is thus a special case of peritoneal ligament, and mesentery is a specific subset of these.

Example: Hepatoduodenal ligament


What is a peritoneal fold? Give an example

A reflection of (parietal) peritoneum that overlies a structure associated with the body wall. It makes a defined border over the covered structure.

Example: Lateral umbilical folds / ligaments - contain inferior epigastric arteries (right and left)


What does intraperitoneal mean?

Also called peritoneal, any organ or structure that is suspended by a mesentary, omentum, or ligament into the abdominal / pelvic cavities


What does retroperitoneal mean?

Any structure or organ that is not suspended by a mesentery and is either fully or partially embedded into the body wall. They are covered by peritoneum, however. Some organs may have intraperitoneal and retroperitoneal regions.

Examples: Kidney, ureter, suprarenal glands, urinary bladder


What is the greater sac?

Larger of two peritoneal-lined spaces, which allows direct access to liver, anterior surface of stomach, colon, small intestines (jejunum and ileum), uterus, and retroperitoneal pelvic structures. It can be accessed through incision thru anterior abdominal wall.


What are the two subdivisions of the greater sac?

1. Supracolic compartment - superior to the transverse colon and its mesentery, including liver, stomach, and spleen. It is partially protected by diaphragm and costal margin
2. Infracolic compartment: inferior to transverse colon and its mesentery. Leads inferiorly to pelic cavity and includes jejunum, ilium, and colon.


What is the lesser sac?

Also known as the omental bursa, it is an enclosed compartment located posterior to the stomach, which is walled off by a series of ligaments, mesenteries, and omentums. Has a single natural outlet claled the epiploic foramen


What are the boundaries of the lesser sac (superior, left, inferior, posterior, anterior)

Superior: Coronary ligament (posterior part), gastrophrenic ligament, and diaphragm.
Left: Gastrophrenic ligament, splenorenal, and gastrosplenic ligaments
Inferior: Transverse mesocolon, greater omentum, and transverse colon
Posterior: Posterior abdominal wall and retroperitoneal structures including pancreas, left adrenal gland, and left kidney
Anterior: Lesser omentum and posterior surface of the stomach.


What is the epiploic foramen? What are its anterior, superior, inferior, and posterior boundaries?

The opening of the lesser sac into the greater sac.
Anterior: Hepatoduodenal ligament
Superior: Caudate lobe of liver
Inferiorly: First part of duodenum
Posteriorly: Inferior vena cava and right crus of diaphragm


What are peritoneal recesses?

Blind pouches formed by folds of peritoneum which open into the peritoneal cavity. They are mostly associated with structures that are transitioning between retroperitoneal and infraperitoneal.


What is the significance of the retrocecal recess?

It is the part of the cecum where the appendix often resides


What are paracolic gutters?

Peritoneal-lined depressions that form between the lateral sides of the ascending and descending colon and the posterior / lateral abdominal wall. It forms a channel where fluid can easily flow from the abdominal cavity to the pelvic cavity or vice versa


What are the functions of the peritoneum?

1. Secrete serous fluid to minimize friction
2. Resist infection by extruding macrophages and other immune cells
3. Form adhesion to wall off an infection or a damaged organ


What is the sensory innervation of the parietal peritoneum?

Sensitive to touch, pain, and temperature via intercostal, lumbar, and sacral nerves.
In the thoracic diaphragram:
Intercostal nerves at margin
Phrenic nerve at central diaphragm


What is the sensory innervation of the visceral peritoneum?

Insensitive to mechanical sensations, however it is sensitive to stretch (VA autonomics)


What are the dividers for the four quadrant system?

4 spaces are defined by a horizontal and vertical plane.
Horizontal: Transumbilical
Vertical: Median plane thru umbilicus


Where is the rough dividing line between the supracolic and infracolic compartment?

The inferior edge of the 10th rib, horizontally


What is the nine-region organization pattern?

Used in clinic:
2 divisions vertically: left and right MCL (midclavicular)
2 divisions horizontally: subcostal and transtubercular plane (iliac tubercles)


What is peritonitis?

Inflammation of peritoneum, often caused by ruptured appendix or perforated bowel leading to infection


What is ascites?

Accumulation of fluid in peritoneal cavity, often associated with cancer (i.e. pancreatic)


What are adhesion?

Fusion of parts of the peritoneum, most common in greater omentum. It is a result of inflammation or trauma (like surgery). They reduce the mobility of the viscera and produce tension that can result in all types of peritoneal pain


What is IP injection?

Intraperitoneal - drugs can be administered rapidly here since the peritoneum has a large surface area


What is one complication of the mobility of the jejunum and ileum? What are common spots of this?

They have the ability to herniate into the abdominal and pelvic cavities.
Common spots:
Inguinal region
Umbilical region
Femoral region

Uncommonly, peritoneal recesses such as a the paraduodenal recess may become herniated.