L7. Anatomy of peritoneal cavity

Question 1

What is the peritoeum? What is the term used to describe the series of folds off the posterior abdominal wall?

Answer 1

The peritoneum is a series of double folds of serous membrane that surrounds the contents of the abdominal cavity. The series of double folds of peritoneum is called the MESENTERY and it connects individual viscera to the posterior abdominal wall.
Each double fold has its own special name.

Question 2

What are the functions of the mesentery?

Answer 2

1. Transmit the neurovascular structures from the posterior abdominal wall (from where they originate - IVC and aorta are retroperitoneal) to the respective intraperitoneal structures.
2. Provides mobility to an intraperitoneal structures. Eg. stomach is able to accommodate food.
3. It shares the nerve supply of the structure it lines (somatic nerve supply for parietal and visceral to visceral peritoneum)

Question 3

Describe the pain felt in the different stages of appendicitis and relate it to the peritoneum

Answer 3

The appendix is in intraperitoneal, inflammation and swelling stretches the mesentery around it.

The pain associated with visceral nerve supply is dull and poorly localised (umbilical region)

Eventually the tip of the appendix will impact on the parietal peritoneum = localised, sharp and severe pain. =
= Localises the pain to about a third of the up from the ASIS to the umbilicus

Question 4

Describe the peritoneal space.

What pathologies can occur in this space?

Answer 4

A potential space only and the advantage of covering with the peritoneum is for friction free glide during movement in peristalsis.

because it has a very large surface area tumours seed leading to rapid spread of tumour

Question 5

What are the most deepest (posterior) part of the abdominal cavity? [3]

Answer 5

RETROPERITONEAL STRUCTURES:
Kidneys (on quadratus lumborum) and the adrenals on top of the kidneys

The ureters (descending on psoas along the line of the lumbar vertebrae)

Question 6

The contents of the abdomen are unpaired structures derived from a primitive gut tube. Describe the dorsal and proximal parts of the mesentery

Answer 6

This tube has a mesentery (dorsal) that connects it to the peritoneum. The proximal part also has the ventral mesentery the falciform ligament to the liver from the anterior abdominal wall.
(see lecture)

Question 7

How do the “secondarily retroperitoneal” structures arise?

What are these structures?

Answer 7

Although all initially intraperitoneal, some structures derived here lose mesentery during development and become retroperitoneal. Mesentery is resorbed thus it ends up as a retroperitoneal structure.

Despite being retroperitoneal, there are still in front of the kidney.

Duodenum and pancreas (Laid on top of the IVC edge to edge of the kidneys), with the bile duct and the ascending and descending colon

Question 8

What overlies the top of the secondarily retroperitoneal structures?

Answer 8

A sheet of parietal peritoneal overlies all of these structures

Question 9

What remaining structures form the intraperitoneal organs?

Answer 9

Liver: placed in right upper quadrant
Spleen upper left with the stomach
Jejunum and Ileum put in the centre and ileocecal region
transverse colon

These are the most superficial layer and are connected to the peritoneal wall (each has one) by the mesentery.

Question 10

Why don’t we have the whole gastrointestinal tube within one giant mesentery? (Why do we have this complex several series of folds system?)

Answer 10

The mesentery can be twisted/undergo torsion (this cuts off the blood supply to the unit) and causes infarcts.

The multiple series of mesentery is a protective arrangement

Question 11

What does it mean by the phrase the gastrointestinal tract has “alternate segmentation of the mesentery”?

Answer 11

Every second section of the gastrointestinal tract is intraperitoneal with mesentery and is therefore mobile and every other section is retroperitoneal and fixed and stable.
Eg. stomach is intraperitoneal for mobility.

This is to allow for flexibility while protecting against torsion and disorganisation

Question 12

Describe the intraperitoneal cavity

Answer 12

It is subdivided into a greater sac (GS) and a lesser sac (LS). The GS makes up a vast majority of the intraperitoneal cavity.

Question 13

What is the omental bursa? What is the function of it?

Answer 13

A space of the cavity that is enclosed behind the stomach.
Behind the stomach is a bursa so that the organ has a bed to expand and contract against.
It is a serous fluid filled space is the lesser sac or the omental bursa

(lesser sac = omental bursa)

Question 14

Does the lesser sac communicate with the greater sac?

Answer 14

The LS communicates with the greater sac at one point only at the epiploic foramen or omental foramen

Question 15

What is The Mesentery? What structure does it surround and connect to the posterior abdominal wall?

Answer 15

Connects the intraperitoneal portion of the small intestine to the posterior wall.
The ROOT of the mesentery (attachment to the posterior abdominal wall)

Question 16

Describe the root of The mesentery

Answer 16

It is the point on the posterior abdominal wall that The mesentery attaches to.

The cut edge extends in an oblique line from the DJF above to the Ileocecum below, crossing the third part of the duodenum and then aorta and IVC, then the psoas towards the ileocecal junction.

Question 17

What is the mesentery of the large intestine (colon) called?

Answer 17

Transverse mesocolon and the sigmoid mesocolon connecting the respective sections to the posterior abdominal wall

Question 18

Describe the attachment of the transverse mesocolon to the posterior abdominal wall

Answer 18

It attaches across the front of the pancreas and the second part of the duodenum.

Question 19

Describe the attachment of the sigmoid mesocolon to the posterior abdominal wall

Answer 19

It has a small inverted ‘V’ shape arising off the wall in front of the left iliac fossa, in the left lower quadrant

Question 20

What structures are also connected to the walls of the abdominal cavity (not necessarily to the posterior wall).

Answer 20

Stomach, gall bladder and liver

Question 21

What are the 2 mesenteries of the stomach? Where to they arise and how do they connect the stomach to the abdominal wall?

Answer 21

The stomach has 2 mesenteries (omentum): lesser omentum connects lesser curvature and greater omentum connecting greater curvature.

They connect the stomach to the diaphragm (superior abdominal wall) indirectly (via the liver)

Question 22

Describe the connections of the lesser omentum

Answer 22

Lesser omentum goes to the liver and surrounds the liver and then up to the diaphragm, connecting it to the superior wall of the cavity via the liver.

It goes up to the under surface (visceral) surface of the liver, it then splits and encloses the liver before it goes up to the top of the cavity (and becomes the coronary and triangular ligaments) and lines the undersurface of the diaphragm.

Question 23

Where does the omental bursa sit in terms of the lesser omentum?

Answer 23

When the duodenum goes behind peritoneum - forms the free edge of the lesser omentum (where the portal triad travels to the liver). Behind the free edge, there is the space behind the stomach: omental bursa

thus it sits behind the lesser omentum

Question 24

What and where is the epiploic foramen?

Answer 24

It is the communication of the greater sac and lesser sac (omental bursa) and this foramen around the free edge.

Question 25

Describe the connections of the greater omentum

Answer 25

Greater omentum off the curvature goes down in front of all abdominal contents and then turns back on itself.

Greater omentum sweeps down forming a “fatty apron” covering all other structures from view. It goes down to the suprapubic region before folding back on itself

Thus it is effectively 4 layers (because it double backs on itself)

Question 26

How does the greater omentum attach to the wall of the abdomen?

Answer 26

As the omentum folds back on itself and then goes back to the retroperiotenal wall, goes over the top of the transverse mesocolon thus attachment is similar to that

Question 27

The lesser omentum also covers the very first inch of the duodenum (the intraperitonal). What does the moving of the duodenum into the retroperitoneal cavity do to the omentum? [2]

Answer 27

1. Creates a free edge
2. Divides it into 2 parts:
   - hepato-gastric from the stomach
   - hepato-duodenal from the duodenal part

Question 28

The fatty apron of the greater apron is only coming off the inferior edge of the stomach (not the whole greater curvature).
Does a greater omentum exist in the superior and lateral edges of the greater curvature?

Answer 28

Yes

Question 29

What are the parts of the greater omentum in the superior and left lateral edges of the greater curvature?

Answer 29

Going higher up the greater curvature (on the left of the stomach) there is still omentum but doesn’t fold down. These go directly to the undersurface of the left dome = GASTRO-PHRENIC LIGAMENT.

The left, middle side of greater omentum (on the side of the spleen) and splits to enclose the spleen before heading back to the posterior abdominal wall = GASTRO-SPLENIC LIGAMENT