The Gut and the Peritoneal Cavity Flashcards
What type of epithelium is the peritoneum?
Simple squamous epithelium – mesothelium
What is contained in the peritoneal cavity?
Nothing - there is only a small amount of fluid and it is a potential space
Which germ layers does the gut tube develop from?
Endoderm and splanchnic mesoderm
What do the peritoneal folds act as a conduit for?
Nerves, blood vessels, lymphatics
What is the difference between intraperitoneal and retroperitoneal?
Intraperitoneal is totally wrapped in peritoneum whereas retroperitoneal is behind the peritoneum and is not totally wrapped in peritoneum.
State three viscera that are secondarily retroperitoneal.
Duodenum, pancreas, colon (ascending and descending only)
State some viscera that were retroperitoneal from the start.
Kidneys, great vessels, adrenal glands, oesophagus, rectum
What are the three divisions of the gut tube and what defines their borders?
Foregut - from the distal 1/3 of the oesophagus to the major duodenal papilla (entrance of the bile duct to the duodenum)
Midgut - 2nd part of the duodenum to 2/3 of the way along the transverse colon
Hindgut - final 1/3 of the transverse colon to the rectum
Which mesenteries suspend the different parts of the gut tube?
The entire gut tube is suspended by dorsal mesentery
The foregut is ALSO suspended by ventral mesentery
What does the ventral mesentery split into?
Falciform ligament and the lesser omentum
How is the lesser sac (omental bursa) formed?
The liver moves right and the stomach and the spleen move left with the dorsal mesentery thus cutting off a space behind the stomach - the lesser sac
What is the lesser omentum?
Fold of peritoneum between the liver and the lesser curvature of the stomach
What is the greater omentum?
Lower part of the dorsal foregut mesentery extends down form the greater curvature of the stomach as the greater omentum. It lies like an apron in front of the intestines.
What are the dorsal and ventral mesogastria?
The mesentery that is joined to the stomach.
Why does the lesser omentum have a lower free border and what opening does that form?
Because it is formed by the ventral foregut mesentery, which ends at the start of the midgut. The opening to the omental bursa is called the epiploic foramen.
What is the transverse colon suspended by?
Transverse mesocolon
What vessels run within the lesser omentum near its free edge?
Hepatic portal vein, hepatic artery proper, bile duct
Describe how the abdomen is divided into different compartments.
The transverse mesocolon divides the abdomen into supracolic and infracolic compartments. The infracolic compartment is further divided by the mesentery of the small intestine (from the duodeno-jejunal flexure to the ileo-caecal valve) - dividing the infracolic compartment into right and left infracolic compartments.
There are also gutters running along the lateral sides of the ascending and descending colon called the right and left paracolic gutter.
Describe the how the direction of movement of peritoneal fluid differs from that of inflammatory exudate.
Peritoneal fluid moves towards the diaphragm
Inflammatory exudate moves towards the pelvis
State the layers of the gut tube.
Mucosa, submucosa, muscularis, serosa/adventitia
Which layers have nerve plexuses and what are they called?
Submucosa - Meissner’s plexus
Muscularis (myenteric) - Auerbach’s plexus
At which vertebral position does the oesophagus penetrate the diaphragm and through which crus?
T10 - through the right crus
What are the different parts of the stomach?
Cardia, fundus, body, pyloric antrum and pyloric canal
What are the four parts of the duodenum?
Superior, descending, inferior, ascending
Superior is where the duodenal cap is located - this is a common location for duodenal ulcers
What is the major duodenal papilla and where is it found?
The major duodenal papilla is the opening of the bile duct to the duodenum - it is in the descending part of the duodenum
Describe three ways in which the jejunum and ileum differ.
Jejunum has a greater diameter, longer vasa recta and less prominent arterial arcades
Describe three ways in which the colon differs from the small intestines.
Colon has taenia coli (ribbons of longitudinal muscle)
Colon has fatty tags - appendices epiploicae
Colon has a segmental/pocketed arrangement
What are the three main arteries supplying the gut and what do each of them supply?
Coeliac Trunk - foregut (and pancreas, liver, spleen)
Superior Mesenteric Artery - midgut
Inferior Mesenteric Artery - hindgut
What does the coeliac trunk divide into?
Common Hepatic Artery
Left Gastric Artery
Splenic Artery
Why does the lesser omentum have a lower free border and what opening does that form?
Because it is formed by the ventral foregut mesentery, which ends at the start of the midgut. The opening to the omental bursa is called the epiploic foramen.
What is the transverse colon suspended by?
Transverse mesocolon
What vessels run within the lesser omentum near its free edge?
Hepatic portal vein, hepatic artery proper, bile duct
Describe how the abdomen is divided into different compartments.
The transverse mesocolon divides the abdomen into supracolic and infracolic compartments. The infracolic compartment is further divided by the mesentery of the small intestine (from the duodeno-jejunal flexure to the ileo-caecal valve) - dividing the infracolic compartment into right and left infracolic compartments.
There are also gutters running along the lateral sides of the ascending and descending colon called the right and left paracolic gutter.
Describe the how the direction of movement of peritoneal fluid differs from that of inflammatory exudate.
Peritoneal fluid moves towards the diaphragm
Inflammatory exudate moves towards the pelvis
State the layers of the gut tube.
Mucosa, submucosa, muscularis, serosa/adventitia
Which layers have nerve plexuses and what are they called?
Submucosa - Meissner’s plexus
Muscularis (myenteric) - Auerbach’s plexus
At which vertebral position does the oesophagus penetrate the diaphragm and through which crus?
T10 - through the right crus
What are the different parts of the stomach?
Cardia, fundus, body, pyloric antrum and pyloric canal
What are the four parts of the duodenum?
Superior, descending, inferior, ascending
Superior is where the duodenal cap is located - this is a common location for duodenal ulcers
What is the major duodenal papilla and where is it found?
The major duodenal papilla is the opening of the bile duct to the duodenum - it is in the descending part of the duodenum
Describe three ways in which the jejunum and ileum differ.
Jejunum has a greater diameter, longer vasa recta and less prominent arterial arcades
Describe three ways in which the colon differs from the small intestines.
Colon has taenia coli (ribbons of longitudinal muscle)
Colon has fatty tags - appendices epiploicae
Colon has a segmental/pocketed arrangement
What are the three main arteries supplying the gut and what do each of them supply?
Coeliac Trunk - foregut (and pancreas, liver, spleen)
Superior Mesenteric Artery - midgut
Inferior Mesenteric Artery - hindgut
What does the coeliac trunk divide into?
Common Hepatic Artery
Left Gastric Artery
Splenic Artery
What are the branches of the superior mesenteric artery?
Jejunal Arteries Ileal Arteries Iliocolic Artery Right Colic Artery Middle Colic Artery
What are the branches of the inferior mesenteric artery?
Left Colic Artery
Sigmoid Arteries
Superior Rectal Artery
Describe the venous drainage of the gut.
The venous drainage does NOT follow the arterial supply. All the venous blood from the gut drains through the liver. The inferior mesenteric vein joins the splenic vein and the splenic vein then joins the superior mesenteric vein to form the hepatic portal vein. The superior mesenteric vein joins the splenic vein behind the first part of the duodenum.
Where do you find portal-systemic anastamosis?
Oesophagus, rectum, umbilicus
Oesophagus: between oesophageal vein and left gastric vein
Umbilicus: between umbilical vein and epigastric veins
Rectum: between superior rectal vein and inferior rectal vein
NOTE: there is a fourth anastomosis between the colic veins and posterior abdominal wall veins
What is the clinical significance of the portal-systemic anastamoses?
If there is liver damage or a blockage then you get portal hypertension leading to dilation of the porto-systemic anastomoses, which could possibly lead to oesophageal or rectal haemorrhage.
Describe the lymphatic drainage of the gut.
The lymphatics follow the arteries. There are coeliac lymph nodes, superior mesenteric lymph nodes and inferior mesenteric lymph nodes. They all drain into the cysterna chyli and then through the thoracic duct.
Which vertebral level is the cysterna chyli positioned at?
(in front of the vertebral body of) L1 and L2
What are the main parasympathetic sensory nerves of the gut?
Vagus Nerve
Pelvic Splanchnic Nerves (S2-S4)
What are the main sympathetic sensory nerves of the gut?
Thoracic Splanchnic Nerves (T5-T12)
Lumbar Splanchnic Nerves (L1+L2)
What are the roles of the parasympathetic sensory and sympathetic sensory nerves of the gut?
Parasympathetic Sensory - involved in regulate reflex gut function
Sympathetic Sensory - mediate pain
What are the three divisions of the thoracic splanchnic nerves?
Greater Thoracic Splanchnic - T5-T9
Lesser - T10-T11
Least - T12
Why are the sensory fibres the most important clinically?
They are involved in mediating pain sensation.
