S2.2 Development of the peritoneal cavity and the foregut

Question 1

In the fourth week the embryo folds. Describe what two types of folding occur

Answer 1

Lateral Folding: Creates ventral body wall and Primitive gut tube

Craniocaudal Folding: Creates cranial and caudal pockets from yolk sac endoderm

Question 2

Describe the regions of the primitive gut tube

Answer 2

Divisible into foregut, midgut and hindgut.

Runs from the stomatodeum to proctodeum, with an opening at the umbilicus into the yolk sac called the viteline duct

Question 3

What are the organs and blood supply of the foregut?

Answer 3

Oesophagus to proximal duodenum

Coeliac trunk T12

Question 4

What are the organs, blood supply and innervation of the midgut?

Answer 4

Distal duodenum to proximal 2/3 transverse colon
SMA L1
Parasympathetic: vagus nerve
Sympathetic: superior mesenteric ganglion

Question 5

What are the organs, blood supply and innervation of the hindgut?

Answer 5

Distal 1/3 transverse colon to upper anal canal
IMA L3
Parasympathetic: pelvic nerve
Sympathetic: inferior mesenteric ganglion

Question 6

How is the coelomic cavity formed?

Answer 6

The mesoderm surrounding the gut splits into Somatic and Splanchnic, and the space between them forms the Coelomic Cavity via lateral folding.

Question 7

What is a mesentery?

Answer 7

A double layer of peritoneum suspending the gut tube from the abdominal wall. This allows conduit for blood and nerve supply, as well as mobility where needed.

Question 8

What is the function of the dorsal and ventral mesentery?

Answer 8

Dorsal mesentery connects the entire developing gut to the roof of the abdominal wall.

The ventral mesentery connects only the foregut to the abdominal floor

Question 9

How are the greater and lesser sacs formed?

Answer 9

The dorsal and ventral mesentery divide the foregut into left and right sacs. The stomach then rotates.

The left sac contributes to the Greater Peritoneal Sac

The right sac contributes to the Lesser Peritoneal Sac, which comes to lie behind the stomach.

Question 10

What divides the greater sac into the supra and infracolic compartments?

Answer 10

The transverse mesocolon

Question 11

How’s does the lesser sac communicate with the greater sac?

Answer 11

Via the (epiploic) foramen of wilmslow

Question 14

What are the attachments of the greater omentum?

Answer 14

Greater curve of the stomach to the transverse colon.

Question 15

What are the attachments of the lesser omentum?

Answer 15

Lesser curve of the stomach to the liver.

Question 16

Describe intraperitoneal and give examples

Answer 16

Some parts of the GI tract, remain suspended from the posterior abdominal wall by a mesentery and remain mobile.
Jejunum, stomach

Question 17

Describe retroperitoneal and give examples

Answer 17

Structures that are not suspended within the abdominal cavity and never had a mesentery.
Aorta, kidneys

Question 18

Describe secondary retroperitoneal and give examples

Answer 18

A structure that developed intraperitoneally, had a mesentery but with successive growth and development the mesentery is lost through fusion at the posterior abdominal wall.
Tail of pancreas, 4th part of duodenum.

Question 19

When does the respiratory primordial begin to develop?

Answer 19

In the 4th week, a respiratory diverticulum forms in the ventral wall of the foregut.

Question 20

How does the respiratory primordium and oesophagus form?

Answer 20

The tracheoesophageal septum divides the respiratory diverticulum, forming the respiratory primordium ventrally and the oesophagus dorsally

Question 21

Describe the peritoneal reflections of the liver

Answer 21

The liver develops from the hepatic bud within the ventral mesentery. Bare area has no peritoneum.