Peritoneal Cavity Flashcards
What are the 3 main functions of the mesenteries?
- transmit vessels that supply intraperitoneal structures
- IVC and aorta lie on the retroperitoneal VC
- allow mobility, peristalsis, and expansion
- retroperitoneal structures are relatively fixed
- GIT has alternating intra (mobile) and retro (fixed) segments
- retroperitoneal structures are relatively fixed
- share nerve supply with the structuries it supplies
- parietal peritoneum - somatic as muscle and skin over it (sharp, severe, localized pain)
- visceral peritoneum - autonomic sensitive to stretch (dull, less well-localized pain that is referred to the midline)
Paired viscera are
retroperitoneal
eg adrenals, kidneys, and ureters
sit against the posterior abdominal wall, with a layer of peritoneum on top
first layer
The primitive gut tube is suspended by
dorsal mesentery from the posterior abdominal wall
ventral mesentery from the anterior abdominal wall (proximal part only)
develops into derivatives of GIT; all are initially peritoneal
Primary retroperitoneal structures
always retroperitoneal, developed there and stayed there
eg kidneys, adrenals, and ureters
Secondary peritoneal structures
become retroperitoneal as part of their development and lose mesentery/fuses with wall
eg ascending and descending colon, duodenum, pancreas, and bile duct
Which unpaired structures are retroperitoneal?
- ascending colon
- descending colon
- duodenum (except first inch)
- pancreas
- bile duct
What comprises the second layer of the peritoneal cavity?
- sitting on top of the first layer: primary retroperitoneal structures (kidneys, adrenals, & ureters)
- ascending & descending colon
- duodenum (except first inch)
- pancreas
- bile duct
Why can’t the entirety of the GIT be in one mesentery?
- twisting of the mesentery would occlude blood supply
- GIT would die
- some components need to be mobile (eg for peristalsis)
- others need to be fixed to prevent twisting
What is the pattern of intra and retroperitoneal structures in the GIT?
- distal oesophagus and stomach - intraperitoneal so they can peristalse and expand
- duodenum - retroperitoneal (except first inch)
- jejunum and ileum - intraperitoneal
- ascending colon - retroperitoneal
- transverse colon - intraperitoneal
- descending colon - retroperitoneal
- sigmoid colon - intraperitoneal
What comprises the third layer of the peritoneal cavity?
intraperitoneal structures with mesenteries attaching them to the abdominal cavity
all are surrounded by visceral peritoneum
- stomach
- jejunum and ileum
- caecum and appendix
- transverse and sigmoid colon
- liver
- gallbladder
- spleen
What is the greater sac?
- comprises the majority of the peritoneal cavity
- what you open into when you open the anterior abdominal wall
- starts at the diaphragm, goes down to pelvic floor
- continuous with the lesser sac (omental bursa) only via the epiploic/omental foramen (of Winslow)
What is the lesser sac?
- aka omental bursa
- smaller subdivision of the peritoneal cavity
- sits behind teh stomach and liver
- continous with greater sac via epiploic/omental foramen (of Winslow)
What are the attachments of ‘the’ mesentery?
- connects ileum and jejunum to the posterior abdominal wall
- starts at the DJ flexure and ends at the ileocecal junction
- the duodenum and the ascending colon are retroperitoneal and don’t need mesentery, so these are the points where it starts and stops
- crosses obliquely, over:
- 3rd part of duodenum
- aorta and IVC
- ureter on R psoas
The mesocolon attaches
the large intestines to the posterior abdominal wall
The transverse mesocolon
- attaches the transverse colon to the posterior abdominal wall
- two layers of peritoneum that leave the posterior abdominal wall at the hepatic and splenic flexures
- crosses over:
- 2nd part of the duodenum
- head and body of pancreas
- these structures are retroperitoneal tf the mesocolon originates from the peritoneum that overlies them
The sigmoid mesocolon
- inverted V-shape
- over the division of the left common iliac artery
The omenta originate from
viscera, not the posterior abdominal wall
The lesser omentum extends from
the lesser curvature of the stomach and first inch of the duodenum
to the inferior/visceral surface of the liver
free edge: contains the portal triad (portal vein, hepatic artery, common hepatic duct) running between the two layers of mesentery
splits and surrounds the liver (liver is intraperitoneal)
under the diaphragm, it reflects to become the diaphragmatic parietal peritoneum
*there is a bare area on the superior liver where the two folds do not cover the liver before they join the diaphragm*
The epiploic/omental foramen of Winslow sits
behind the free edge of the lesser omentum
The greater omentum of the liver extends from
the greater curvature of the stomach
attaches to the first part of the duodenum
What is the course of the distal part of the greater omentum?
- greater curvature of stomach and first part of duodenum
- drapes down over the front of the rest of the abdominal viscera (transverse colon, jejunum, ileum)
- then turns inferiorly and posteriorly and heads back up
- crosses over the top of and adheres to the transverse colon and mesocolon
- tf the greater omentum is 4 layers of peritoneum
- follows the attachment of the mesocolon to the posterior abdominal wall
- ie 2nd part of duodenum and pancreas
- creates the fatty apron
- known as the gastrocolic ligament
What is the course of the proximal part of the greater omentum?
- middle part forms the gastrolineal ligament that envelops the spleen (intraperitoneal) to get to the posterior abdominal wall
- superior part forms the gastrophrenic ligament attaching to and forming the parietal peritoneum of the undersurface of the diaphragm on the left hand side
