The Gut and the Peritoneal Cavity

Question 1

What type of epithelium is the peritoneum?

Answer 1

Simple squamous epithelium – mesothelium

Question 2

What is contained in the peritoneal cavity?

Answer 2

Nothing - there is only a small amount of fluid and it is a potential space

Question 3

Which germ layers does the gut tube develop from?

Answer 3

Endoderm and splanchnic mesoderm

Question 4

What do the peritoneal folds act as a conduit for?

Answer 4

Nerves, blood vessels, lymphatics

Question 5

What is the difference between intraperitoneal and retroperitoneal?

Answer 5

Intraperitoneal is totally wrapped in peritoneum whereas retroperitoneal is behind the peritoneum and is not totally wrapped in peritoneum.

Question 6

State three viscera that are secondarily retroperitoneal.

Answer 6

Duodenum, pancreas, colon (ascending and descending only)

Question 7

State some viscera that were retroperitoneal from the start.

Answer 7

Kidneys, great vessels, adrenal glands, oesophagus, rectum

Question 8

What are the three divisions of the gut tube and what defines their borders?

Answer 8

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

Question 9

Which mesenteries suspend the different parts of the gut tube?

Answer 9

The entire gut tube is suspended by dorsal mesentery

The foregut is ALSO suspended by ventral mesentery

Question 10

What does the ventral mesentery split into?

Answer 10

Falciform ligament and the lesser omentum

Question 11

How is the lesser sac (omental bursa) formed?

Answer 11

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

Question 12

What is the lesser omentum?

Answer 12

Fold of peritoneum between the liver and the lesser curvature of the stomach

Question 13

What is the greater omentum?

Answer 13

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.

Question 14

What are the dorsal and ventral mesogastria?

Answer 14

The mesentery that is joined to the stomach.

Question 15

Why does the lesser omentum have a lower free border and what opening does that form?

Answer 15

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.

Question 16

What is the transverse colon suspended by?

Answer 16

Transverse mesocolon

Question 17

What vessels run within the lesser omentum near its free edge?

Answer 17

Hepatic portal vein, hepatic artery proper, bile duct

Question 18

Describe how the abdomen is divided into different compartments.

Answer 18

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.

Question 19

Describe the how the direction of movement of peritoneal fluid differs from that of inflammatory exudate.

Answer 19

Peritoneal fluid moves towards the diaphragm

Inflammatory exudate moves towards the pelvis

Question 20

State the layers of the gut tube.

Answer 20

Mucosa, submucosa, muscularis, serosa/adventitia

Question 21

Which layers have nerve plexuses and what are they called?

Answer 21

Submucosa - Meissner’s plexus

Muscularis (myenteric) - Auerbach’s plexus

Question 22

At which vertebral position does the oesophagus penetrate the diaphragm and through which crus?

Answer 22

T10 - through the right crus

Question 23

What are the different parts of the stomach?

Answer 23

Cardia, fundus, body, pyloric antrum and pyloric canal

Question 24

What are the four parts of the duodenum?

Answer 24

Superior, descending, inferior, ascending

Superior is where the duodenal cap is located - this is a common location for duodenal ulcers

Question 25

What is the major duodenal papilla and where is it found?

Answer 25

The major duodenal papilla is the opening of the bile duct to the duodenum - it is in the descending part of the duodenum

Question 26

Describe three ways in which the jejunum and ileum differ.

Answer 26

Jejunum has a greater diameter, longer vasa recta and less prominent arterial arcades

Question 27

Describe three ways in which the colon differs from the small intestines.

Answer 27

Colon has taenia coli (ribbons of longitudinal muscle)
Colon has fatty tags - appendices epiploicae
Colon has a segmental/pocketed arrangement

Question 28

What are the three main arteries supplying the gut and what do each of them supply?

Answer 28

Coeliac Trunk - foregut (and pancreas, liver, spleen)
Superior Mesenteric Artery - midgut
Inferior Mesenteric Artery - hindgut

Question 29

What does the coeliac trunk divide into?

Answer 29

Common Hepatic Artery
Left Gastric Artery
Splenic Artery

Question 30

What are the branches of the superior mesenteric artery?

Answer 30

Inferior Pancreatico-Duodenal Arteries
Jejunal Arteries
Ileal Arteries
Iliocolic Artery
Right Colic Artery
Middle Colic Artery

Question 31

What are the branches of the inferior mesenteric artery?

Answer 31

Left Colic Artery
Sigmoid Arteries
Superior Rectal Artery

Question 32

Describe the venous drainage of the gut.

Answer 32

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.

Question 33

Where do you find portal-systemic anastamosis?

Answer 33

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

Question 34

What is the clinical significance of the portal-systemic anastamoses?

Answer 34

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.

Question 35

Describe the lymphatic drainage of the gut.

Answer 35

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.

Question 36

Which vertebral level is the cysterna chyli positioned at?

Answer 36

(in front of the vertebral body of) L1 and L2

Question 37

What are the main parasympathetic sensory nerves of the gut?

Answer 37

Vagus Nerve

Pelvic Splanchnic Nerves (S2-S4)

Question 38

What are the main sympathetic sensory nerves of the gut?

Answer 38

Thoracic Splanchnic Nerves (T5-T12)

Lumbar Splanchnic Nerves (L1+L2)

Question 39

What are the roles of the parasympathetic sensory and sympathetic sensory nerves of the gut?

Answer 39

Parasympathetic Sensory - involved in regulate reflex gut function
Sympathetic Sensory - mediate pain

Question 40

What are the three divisions of the thoracic splanchnic nerves?

Answer 40

Greater Thoracic Splanchnic - T5-T9
Lesser - T10-T11
Least - T12

Question 41

Why are the sensory fibres the most important clinically?

Answer 41

They are involved in mediating pain sensation.