Peritoneal Cavity

Question 1

What the potential space between the parietal and visceral peritoneum?

Answer 1

Peritoneal cavity

Question 2

What is a mesentery?

Answer 2

Two layers are continuous where the parietal layer reflects off the abdominal wall onto the viscera

Question 3

What are retroperitoneal viscera?

Answer 3

Viscera that lie within the posterior abdominal wall, with parietal peritoneum covering their anterior surface only.

Question 4

What are intraperitoneal viscera?

Answer 4

Suspended from the abdominal wall by a mesentery with a double layer of peritoneum.

Question 5

How is the IVC and the aorta organised in terms of I/R?

Answer 5

• IVC and aorta are retroperitoneal, overly the lumbar vertebral column and are retroperitoneal- lie behind the peritoneum on the posterior abdominal wall. Therefore any branches of vessels and nerves are transmitted to intraperitoneal structures via their mesenteries.

Question 6

Where do intraperitoneal viscera get their blood supply from?

Answer 6

Intraperitoneal structures get their vascular supply and nerve supply from the posterior abdominal wall via the mesentery but mesenteries are also for movement that is unique to intraperitoneal viscera- important for peristalsis and distension.

Question 7

Why is not sensible to have all blood supply in the mesentery, but at the same time why is it not sensible for it to be retroperitoneal?

Answer 7

Mesentery could also twist in the case of a bolbulus- cutting off the vessels in the mesentery and the bowel dies. Therefore, not sensible to have everything in a mesentery but not sensible to have everything retroperitoneal because then it could not distend and allow for proper digestions.

Question 8

How do we overcome the issue of not wanting to be mesenteric but not retroperitoneal either?

Answer 8

GIT has segments with the mesentery that alternate with segments that fixed, retroperitoneal. Get the benefits of having a mesentery- mobility and expansion without the risk of twisting by alternating with stability given by retroperitoneal viscera.

Question 9

What is the visceral peritoneum supplied by?

Answer 9

Visceral peritoneum supplied by the autonomic nerves supplying the viscus and sensitive only to stretch so visceral peritoneum will refer pain that is dull, less well defined and referred to middline.

Question 10

What is the parietal peritoneum supplied by?

Answer 10

Innervated by somatic nerves. Any irritation of the parietal peritoneum produces severe and sharply localized nerves

Question 11

Explain how pain occurs during appendicitis as a result of the nerve innervation.

Answer 11

-Visceral peritoneum stretches and pain will be referred to the midline and because visceral nerve supply- pain is dull and poorly localized in the region of the umbilicus.
- As the appendix continues to swell, will touch the anterior abdominal wall and inflames the parietal peritoneum lining it (innervated by somatic nerves). Suddenly, the patient feels sharp pain in a highly localized area overlying the appendix.
=This indicates the transference from autonomic nerve supply of the visceral peritoneum responding to stretch to the somatic nerve supply of the parietal peritoneum with its pains sensitive structures.

Question 12

What are examples of paired structures and where are they located?

Answer 12

The paired structures (kidneys, adrenals and the ureters) are retroperitoneal (located directly on the posterior abdominal wall with the abdominal aorta and IVC.

Question 13

Where do all the unpaired viscera derive from and give examples of them?

Answer 13

Derived from the gastrointestinal tract (initially primitive gut tube), have kept their mesentery.
Distal oesophagus down to rectum and anal canal (tubular part of GIT) + liver, gall bladder, pancreas and spleen are all derived from primitive gut tube

Question 14

Where was the primitive gut tube and by type of mesentery was it suspended from the posterior and anterior abdominal wall?

Answer 14

Was CENTRALLY placed tube suspended from the posterior abdominal wall by a posterior full-length mesentery called the dorsal mesentery and from the anterior abdominal wall by a short, proximal ventral mesentery connecting it to the anterior abdominal wall.

Question 15

What are secondary retroperitoneal organs?

Answer 15

They also go behind the peritoneum (retroperitoneal) but will go in front of the structures that have always been there- the kidneys, ureter and adrenals.
EXAMPLES: duodenum and pancreas, the bile duct and also the ascending and descending colon

Question 16

Describe the alternate segment arrangement of the GIT.

Answer 16

Stomach and last part of esophagous are intraperitoneal so duodenum will be retroperitoneal, jejenum and ileum, as well as caeum + appendix are intraperitoneal, ascending colon is retroperitoneal, transverse colon intraperitoneal , descending colon retroperitoneal, sigmoid colon intraperitoneal.

Question 17

What sacs is the abdominal cavity divided into?

Answer 17

Abdominal cavity subdivided into the greater sac (GS) and lesser sac (LS).

Question 18

What is the greater sac?

Answer 18

Greater sac accounts for most of the space in the peritoneal cavity- beginning superiorly at the diaphragm and continuing down into the pelvic cavity to the pelvic floor. When you cut someone open from the anterior abdominal wall, opened into the greater sac of the peritoneal cavity.

Question 19

What is the lesser sac?

Answer 19

Lesser sac (AKA omental bursa) is a smaller subdivision. Part of the peritoneal cavity behind the stomach- a smaller space that allows the stomach to expand into it and glide easily. Omental bursa is a fluid filled space that allows for smooth movement (few mls of serous fluid) behind the stomach, between it and the abdominal wall.

Question 20

What is the communication between the greater and lesser sac?

Answer 20

Epiploic (omental) foramen (of Winslow.

There is only one communication between the greater sac and the lesser sac via.

Question 21

How is THE MESENTERY attached?

Answer 21

THE’ mesentery: term used for the large, fan-shaped, double-folded peritoneum connecting the jejenum and ileum to the posterior abdominal wall. Seen above. If you want to take out jejenum and ileum, cut off jejenum at the DJ-flexure and terminal part of the ileum but cannot move out of the abdominal cavity until you have divided the root of the mesentery.
àConnects to the posterior abdominal wall from the DJ flexure superiorly, obliquely downwards and across the third part of the duodenum, the aorta, the IVC and the right ureter on psoas and extends down to the iliocaecal junction.

Question 22

Construct the layers of the abdominal cavity in terms of deep to superficial.

Answer 22

• First thing we put in are the deepest layer paired viscera (adrenals, kidneys and ureters) deep against the posterior abdominal wall, on psoas and quadratus lumborum.
• Next, put the middle layer of secondary retroperitoneal structures, including the duodenum, pancreas, ascending and descending colon.
  =These are structures that derive from the primitive gut tube but lose their mesentery and settle on the posterior abdominal wall during their development. Thus, they will always be in front of the kidneys, ureters and adrenals.
  àPut over the first and second layers the parietal peritoneum because all of these structures are retroperitoneal.
• Lastly, the most superficial intraperitoneal structures which rest directly against the anterior abdominal wall.
  =Liver into the RUQ, stomach and spleen into the LUQ, the coils of the small intestine going into the centre, transverse colon going across the top, sigmoid colon looping down in the LUQ. Each have a mesentery attaching them to the peritoneum of posterior abdominal wall (overlying not just the posteriori abdominal wall but the deep and middle layer of retroperitoneal structures.

Question 23

What are the 3 mesentery names?

Answer 23

1. Transverse mesocolon
2. “The Mesentery”
3. Sigmoid mesocolon

Question 24

Explain the mesentery of transverse colon.

Answer 24

• Double fold of peritoneum connecting the transverse colon to the posterior abdominal wall and the retroperitoneal structures overlying it.
• Mesentery leaves the posterior abdominal wall traverses across the anterior surface of the head and body of the pancreas, and the second vertical part of the duodenum.
• Nerves, vessels and lymphatics running in this mesentery between the layers of the transverse mesocolon out to the transverse colon.

Question 25

Explain the mesentery of the sigmoid colon.

Answer 25

• Sigmoid mesocolon is much smaller, an inverted, V- shaped double fold of peritoneum.
• Attaches the sigmoid colon to the posterior abdominal wall over the division of the left common iliac artery (deep down in the pelvis).

Question 26

What is the omenta?

Answer 26

• Sigmoid mesocolon is much smaller, an inverted, V- shaped double fold of peritoneum.
• Attaches the sigmoid colon to the posterior abdominal wall over the division of the left common iliac artery (deep down in the pelvis).

Question 27

What is the lesser omentum?

Answer 27

• Extends from the lesser curvature of the stomach and the first part of duodenum (duodenal cap) which is the only part of the duodenum that is intraperitoneal, to the inferior surface/ visceral surface of the liver. Will rap around the liver (bc it is intraperitoneal also) from the visceral surface onto diaphragmatic surface and then from the diaphragmatic surface of the liver onto the under surface of the diaphragm.
  àInstead of going to the posterior abdominal wall, going to the diaphragm (superior wall) and instead of going straight there, it surrounds the liver on route. However, does not completely surround the liver in a perfect double fold but it leaves an area on the diaphragmatic surface bare (has no peritoneum covering it).
  =Ends abruptly where the duodenum becomes retroperitoneal, because from there on the 2nd, 3rd and 4th parts of the duodenum are retroperitoneal.
  =Free edge of the lesser omentum has running in it the portal triad (hepatic artery, portal vein and common bile duct)

Question 28

What is the greater omentum?

Answer 28

• Double fold of peritoneum coming off the greater curvature of the stomach and connecting it to thewalls aof the abdominal cavity. Greater omentum comes off the whole of the greater curvature, but different components of the greater omentum will do different things in their journey to the posterior abdominal wall.

Question 29

What is the vast majority of the greater omentum made from, and how is it attached?

Answer 29

Gastrocolic ligament.
Which instead of going straight to the posterior abdominal wall, it extends downwards as the fatty apron in front of the jejenum and the ileum, befor turning back on itself and heading to the posterior abdominal wall. Thus has four layers of peritoneum- two heading down, and another two heading up.

Question 30

How many layers of peritoneum does the greater omentum have?

Answer 30

4 layers, 2 heading down, and another two heading up.

Question 31

Which part of the greater omentum cannot give rise to the fatty apron, and which part can?

Answer 31

Proximal part- CANNOT

Distal part - CAN

Question 32

Explain the proximal part of the greater omentum.

Answer 32

• Very top goes up to the under surface of the left dome of the diaphragm and is called the gastrophrenic ligament.
• Middle part goes via spleen. Heads off from the greater cuvature, splits to head around the spleen before attaching to the posterior abdominal wall overlying the left kidney (just as the lesser omentum splits around the liver).