Peritoneum Flashcards
What is the peritoneum?
It is a single layer of squamous epithelium (mesothelium) that is derived from the mesoderm layer of the developing embryo.
The peritoneum forms a ______ membrane.
Serous membrane which invests most of the digestive, reproductive organs, and the walls of the abdominal and pelvic cavities
What is the peritoneal cavity?
The complete coverage of all organs by the peritoneum in the abdominal and pelvic cavities creates a mesothelial-lined cavity (or sac) called the peritoneal cavity, which is void of exposed organs
What are the exceptions to the peritoneal cavity covering?
Fimbriae and the opening of the uterine tube.
The peritoneal cavity exists as a potential space that contains only ________ and occasional macrophages in the healthy person.
Serous fluid
As the developing embryo elongates and the primitive gut begins to the close, the future abdominal and pelvic cavities are divided rostral-caudally by:
A double-lined mesothelium (dorsal-mesoduodenum and dorsal mesocolon) that has its origin at the base of the aorta and its insertion at the midline above the umbilicus on the ventral surface (ventral-mesogartrium)
Clusters of cells in the dorsal mesogastrium give rise to:
The pancreas and the spleen
Clusters of cell in the ventral mesogastrium gives rise to:
The liver
The peritoneum consists of what two layers?
- Parietal layer - lines the abdominal and pelvic walls
2. Visceral layer - invests the viscera of the abdominal and pelvic organs
Is the peritoneal cavity open or closed in males?
It is closed - there is no natural communication between the peritoneal cavity and the outside environment in the male.
Is the peritoneal cavity open or closed in females?
It is open - the opening of the uterine tube is not covered by peritoneum. This accommodates the transport of the ovulated egg from the peritoneal cavity into the uterine tubes. There is direct communication from the peritoneal cavity to the outside environment via uterine tube-uterus-cervix-vagina.
What is the significance of the peritoneal cavity being open in females?
It is a pathway for potential spread of infections that may arise anywhere along the urogenital tract
What is the parietal peritoneum separated from the body wall by?
The extra peritoneal connective tissue
What specialized structures does the peritoneum form?
Mesentery, omentum, ligament, and peritoneal folds
What is the mesentery?
Double layer of peritoneum attached to the body wall that encloses part or all of an organ and its supply of vessels (arteries, veins, and lymphatics) and nerves. An organ suspended by mesentery is mobile.
What are some examples of mesentery?
Transverse mesocolon, the mesentery, mesoappendix, and sigmoid mesocolon
What is omentum?
A double-layered fold of peritoneum (mesentery) passing from the stomach and first part of the duodenum to another abdominal organ
What is the Greater omentum?
It attaches to the greater curvature of the stomach (and the first part of the duodenum) and inserts onto the transverse colon
What is the Lesser omentum?
It attaches along the lesser curvature of the stomach and first part of the duodenum and inserts onto the visceral surface (inferior surface) of the liver.
What is important about the greater and lesser omenta?
They are very elastic and can accommodate the movement and stretching of the stomach and transverse colon
What is the peritoneal ligament?
It is defined as a mesentery or omental structure that is strengthened by underlying connective tissue. Ligaments are less susceptible to stretching than omentums and mesenteries and serve as anchoring points for suspended organs
What are some examples of peritoneal ligaments?
Hepatoduodenal, gastrosplenic, splenorenal, and gastrophrenic, and falciform, and the coronary ligament of the liver
What is a peritoneal fold?
A reflection of peritoneum that overlies a structure associated with the body wall. This results in the formation of a defined border over the covered structure.
What are some examples of peritoneal folds?
Median-, medial-, and lateral-umbilical folds
What is the median-umbilical fold remnant of?
The urachus
What is the medial-umbilical fold remnant of?
The umbilical arteries - right and left
What is in the lateral-umbilical fold?
Inferior epigastric vessels - right and left
Structure - organs, vessels, ducts etc - in the abdominal and pelvic cavities are defined as being:
Intraperitoneal or retroperitoneal
What does intraperitoneal mean?
Defines any organ or structure that is suspended by a mesentery, omentum, or ligament into the abdominal or pelvic cavity
What does retroperitoneal mean?
Defines any structure or organ that is not suspended by a mesentery and is either fully or partially embedded into the body wall. These structures ARE covered by the peritoneum.
What are examples of structures that are retroperitoneal?
Kidney, ureter, suprarenal glands, and urinary bladder.
Some organs have regions that are both intraperitoneal and retroperitoneal. What are some examples?
The duodenum has 4 regions. 1 and 4 are intraperitoneal and 2 and 3 are retroperitoneal
The peritoneal is subdivided into:
The greater and lesser sacs
What is the greater sac?
It is the larger of the 2 peritoneal-lined spaces, which allows direct access to the liver, anterior surface of the stomach, the colon, small intestines (jejunum and ileum) and the uterus and retroperitoneal structures located in the pelvis. Can be accessed by surgical incision thru the anterior abdominal wall
The greater sac is subdivided into 2 compartments:
Supracolic and infracolic compartments
What defines the supracolic compartment?
This area is superior to the transverse colon and its mesentery and is partially under cover of the costal margin and the diaphragm.
What structures are related to the supracolic compartment?
Liver, stomach, and spleen
WHat defines the infracolic compartment?
This region is located inferior to the transverse colon (and its mesentery) and leads inferiorly into the pelvic cavity
What structures are related to the infracolic compartment?
Jejunum, ilium, 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.
What is the epiploic foramen?
In the normal individual, the lesser sac has a single natural outlet that communicates with the greater sac (epiploic foramen)
What is the superior boundary of the lesser sac?
Posterior part of coronary ligament of the liver and diaphragm
What is the left boundary of the lesser sac?
The gastrophrenic, splenorenal, and gastrosplenic ligaments
What is the inferior boundary of the lesser sac?
The transverse mesocolon, the greater omentum, and the transverse colon
What is the posterior boundary of the lesser sac?
The posterior abdominal wall and retroperitoneal structures including the pancreas, left adrenal gland and the left kidney
What is the anterior boundary of the lesser sac?
The posterior wall of the stomach and the lesser omentum
Which ligament expands and stores blood when we sleep?
Gastrosplenic ligament
What is the epiploic foramen?
Located on the upper right side of the peritoneal cavity, it is the only natural communication between the greater and lesser sacs
What is the anterior boundary of the epiploic foramen?
The hepatoduodenal ligament (containing the portal vein, common bile duct and proper hepatic artery)
What is the superior boundary of the epiploic foramen?
The caudate lobe of the liver
What is the inferior boundary of the epiploic foramen?
The first part of the duodenum
What is the posterior boundary of the epiploic foramen?
The vena cava and the right crus of the diaphragm
What are peritoneal recesses?
Blind pouches formed by folds of peritoneum which open into the peritoneal cavity. These recesses are mostly associated with structures that are transitioning between being retroperitoneal to peritoneal.
Describe the paraduodenal recess:
Where the 3rd-4th part of the duodenum (retroperitoneal-peritoneal) transitions to the start of the jejunum (peritoneal)
Describe the retrocecal recess:
Transition from the ilium (peritoneal) to the ascending colon at the cecal region
What is the third peritoneal recess?
Intersigmoid recess
What are paracolic gutters?
They are peritoneal-lined depressions that form between the lateral sides of the ascending and descending colon and the posterior/lateral abdominal wall. This depression forms a channel, whereby fluids can easily flow from the abdominal cavity into the pelvic cavity and vice verse
What is the primary function of the peritoneum?
To secrete a serous fluid, which aids to minimize friction of the moving intraperitoneal structures in the abdominal and pelvic cavities.
What are some of the other functions of the peritoneum?
It resists infection by extruding macrophages, and other immune cells into the peritoneal cavity and has the ability to form adhesions to wall off an infection or a damaged organ (ie greater omentum). It also has a very large surface area (second to skin) and a very rapid absorption capacity for water, metabolites, injectable drugs etc
Which peritoneum is sensitive to touch?
Parietal
The parietal perituneum is innervated by:
Intercostal, lumbar and sacral nerves
Sensory innervation to the peritoneal surface of the thoracic diaphragm is provided by:
- Intercostal nerves to the costal margin of the diaphragm
2. Phrenic n (C3-C5) to the central diaphragm
The visceral peritoneum is insensitive to mechanical sensations such as touch and temperature but, like the visceral pericardium and pleura, it is sensitive to:
Stretch
What is the Four-Quadrant Pattern?
Gives rise to 4 spaces defined by a horizontal plane and a vertical plane thru the umbilicus
What is the horizontal plane called?
Transumbilical plane
What is the vertical plane?
Median plane
These two planes subdivide the peritoneal cavity into 4 compartments:
The right and left upper quadrants and the right and left lower quadrants
What is the Nine-Region Pattern?
Subdivides abdominal and pelvic regions into 9 segemnts defined by 2 vertical planes bisecting the clavicles and two horizontal planes, a subcostal planes, and a transtubercular plane (inferior)
What is peritonitis?
Inflammation of the peritoneum. A ruptured appendix or perforated bowel is common cause of peritonitis and is life threatening
Describe what adhesions are:
Inflammation or trauma (ie post-surgical) to the peritoneum may result in adhesions (fusion of parts of the peritoneum).
What is significant about adhesions?
They may reduce the mobility of the viscera and produce tension that can result in peritoneal pain (visceral, parietal, or both)
What is ascites?
The accumulation of fluid in the peritoneal cavity
Why are medications rapidly administered by intraperitoneal injection?
Because the peritoneum readily transports drugs and anesthetics
What happens in the case of a hernia?
The jejunum and ileum are extremely mobile and have the ability to blunt-dissect their way out (herniate) of the abdominal and pelvic cavities. Commone places of herniation include: inguinal, umbilical, and femoral regions, however peritoneal recesses, such as the paraduodenal recess, are also sites where the small intestine can dissect its way in. Could be life threatening and could lead to surgical intervention
