Session 2 - Development of the GI tract

Question 1

Name the foregut derivatives

Answer 1

• Oesophagus
• Stomach
• Pancreas, liver and gall bladder
• Proximal duodenum

Question 2

Name the midgut derivatives

Answer 2

• Distal duodenum
• Jejunum, ileum, cecum, ascending colon
• Proximal 2/3 of transverse colon

Question 3

Name the hindgut derivatives

Answer 3

• Distal 1/3 of transverse colon
• Descending colon, sigmoid colon, rectum
• Upper anal canal and
• internal lining of bladder and urethera

Question 4

How can the foregut, midgut, and hindgut be differentiated?

Answer 4

Dstinct branches of the aorta supplies each part

Question 5

What structures have a mixed blood supply and why?

Answer 5

structures that develop close to the junction between foregut and midgut have a mixed blood supply:

• Duodenum
• Pancreas head

Question 6

How is the abdominal cavity and the thoracic cavities formed?

Answer 6

During folding the intraembryonic coelom comes together and forms a large cavity. This is later divided in 2 by the diaphragm to form the 2 cavities.

Question 7

Label the following

Answer 7

Question 8

How is the mesentery formed?

Answer 8

• During the yolk sac being pinched off, the primitive gut tube moves into the peritoneal cavity
• Suspended by mesoderm which later goes on to form the mesentery.

Question 9

What segments of the primitive gut tube are suspended by dorsal and ventral mesentery?

Answer 9

Foregut

Question 10

Explain how the greater and lesser sacs form.

Answer 10

At the foregut, dorsal and ventral mesentery divide the cavity into left and right.

Stomach rotates clockwise, moving the dorsal mesentery to the right and the ventral mesentery to the left.

Results in the right sac being behind the stomach (forms lesser sac) and the left sac being in front of the stomach (forms greater sac)

Question 11

What do the dorsal and ventral mesenteries become?

Answer 11

Dorsal - greater omentum

Ventral - lesser omentum

Question 12

What develops in the dorsal and ventral mesenteries?

Answer 12

Dorsal - spleen

Ventral - liver

Question 13

Explain the development of the trachea

Answer 13

A respiratory diverticulum forms from the ventral wall of the foregut, pinches off via the tracheoesophageal septum, and becomes the trachea

Question 14

Why do retroperitoneal structures not have a mesentery?

Answer 14

they were never in the peritoneal cavity

Question 15

Name 4 secondarily retroperitoneal structures.

Answer 15

PADD

P - pancreas

A - ascending colon

D - Descending colon

D - Duodenum