Development of the Digestive Tract - Banks

Question 1

The derivatives of the foregut are: (5)

Answer 1

(1) pharynx and its derivatives (discussed next quarter);
(2) lower respiratory system (not addressed);
(3) esophagus and stomach;
(4) proximal duodenum (cranial to and including the opening of the bile duct);
(5) pancreas and liver (with its biliary apparatus)

Question 2

Development of the Spleen

skip, not on hot slides

Answer 2

Develops from a mass of mesenchymal
cells located between the layers of the
dorsal mesentery of the stomach.

Question 3

The derivatives of the midgut are: (4)

Answer 3

1. small intestine (distal ½ duodenum, jejunum, ileum)
   
   2. cecum with vermiform appendix
   3. ascending colon with right colic flexure
   4. most of transverse colon (prox. 2/3rds)

Question 4

Fixation:

Answer 4

Attachment of dorsal mesentery greatly modified after intestines return to abdominal cavity.
Mesenteries pressed against posterior abdominal wall
Mesentery of ascending / descending colon fuses with parietal peritoneum RETROPERITONEAL
colon presses duodenum against posterior abdominal wall retroperitoneal.

Question 5

Retraction:

Answer 5

Reduction of midgut hernia. Intestines return to abdominal cavity, they undergo a 180 degree clockwise rotation.

Total of 270 degrees rotation.

Question 6

Rotation:

Answer 6

Midgut loop rotates 90 degrees counterclockwise. Formed by superior mesenteric artery.

Question 7

Herniation:

Answer 7

As midgut lengthens, it forms a ventral U-shaped loop, the midgut loop

Question 8

B. Four stages in the development of the midgut, in order:

Answer 8

1. Herniation due to elongation of the loop
   
   2. Rotation. . .
   3. Retraction. . .
   4. Fixation. . .

Question 9

A. The derivatives of the hindgut are:

Answer 9

1. left part of the transverse colon (left colic flexure)
   
   2. descending colon
   3. sigmoid colon
   4. rectum
   5. superior portion of the anal canal

Question 10

Development of the pancreas:

Ventral pancreatic bud becomes…
Dorsal pancreatic bud becomes…

Answer 10

Ventral pancreatic bud becomes most of the head of pancreas
Dorsal pancreatic bud becomes remainder of pancreas

Question 11

Development of stomach:

Answer 11

First rotates 90 degrees clockwise around long. axis
Left side face anteriorly and right side face posteriorly.
after rotation, dorsal mesentery of greater curvature hangs caudally GREATER OMENTUM
second rotation results in formation of omental bursa (lesser peritoneal sac)
Communication between sacs via epiploic foramen (foramen of winslow)