Development of the GI tract

Question 1

What part of the primitive embryo forms into the gut?

Answer 1

Endoderm

Question 2

What are the 3 parts of the gut and their distinctions?

Answer 2

Foregut - oesophagus, stomach, ventral duodenum, liver, pancreas, biliary apparatus
Midgut - dorsal duodenum, jejunum, ileum, caecum, ascending colon, 2/3 transverse colon
Hindgut - last 1/3 of the transverse colon, descending colon, sigmoid colon, rectum

Question 3

What are the mesenteries of the gut?

Answer 3

Foregut has dorsal and ventral mesentery. Hence is conencted to the body wall.
Midgut and hindgut only have dorsal mesentery.

Question 4

Which germ layer gives rise to the wall of the gut tube, mesenteries and smooth muscle?

Answer 4

The mesoderm.

Question 5

Where does blood supply to the foregut originate from?

Answer 5

Coelic trunk

Question 6

Where does blood supply to the midgut originate from?

Answer 6

Superior mesenteric artery - branches off the aorta

Question 7

Where does the blood supply to the hindgut originate from?

Answer 7

Inferior mesenteric artery - branches off the aorta.

Question 8

What vessel supplies the abdominal oesophagus?

Answer 8

Left gastric artery - branches from the coeliac trunk

Question 9

What is the venous drainage of the oesophagus?

Answer 9

Via the left gastric vein to the portal system.

Via the azygous vein to the systemic circulation.

Question 10

Where does the GI tract initially extend from and to in the primitive embryo?

Answer 10

From the buccopharyngeal membrane to the cloacal membrane.

Question 11

How is the large mid-gut generated?

Answer 11

Lateral embryonic folding which pinches off a pocket of the yolk sac.

Question 12

How is the oral cavity formed?

Answer 12

Breakdown of the buccopharyngeal membrane. Mainly contributted to by the pharynx lining within pharyngeal arches.

Question 13

How does the respiratory tract form from the foregut?

Answer 13

A ventral bud arises which grows downwards and buds off from the developing oesophagus.

Question 14

What is recanalisation? (occurs in development of the foregut)

Answer 14

The initial hollow collumn gets filled in by overproduction of cells. Recanalisation begins to form holes in the centre of the tube which reopens up the tube.

Question 15

How does the pancreas develop?

Answer 15

Ventral and dorsal pancreas develop from opposite sides of the gastric tube below the stomach swelling.
Ventral pancreas swings around to the left to the dorsal pancreas. The ductile systems of the pancreases fuse at the incinate process of the pancreas.

Question 16

What is midgut herniation?

Answer 16

Midgut develops external to the abdomen during development.

Question 17

What is the significance of midgut rotation?

Answer 17

To place the GI tract in the correct abdominal position with its associated mesentry.

Question 18

How are the mesenteries of the GI tract generated?

Answer 18

The mesenteries of the GIT are generated from the common dorsal mesentery. The ventral mesentery contributes to the lesser omentum and the falciform ligament

Question 19

Two twists occur in the development of the mid gut. When and to what degree do these occur?

Answer 19

90 degree turn between 42 and 50 days.

180 degree turn at 76 days.

Question 20

What is the hindgut derived from?

Answer 20

The cloaca and cloacal membrane.

Question 21

What does the cloaca develop into?

Answer 21

The rectum, anal canal, bladder and urethra.

Question 22

How does the urinary and gastrointestinal system seperate from eachother?

Answer 22

Cloacal membrane is perforated. Urorenal septum comes down and connects with the cloacal membrane to seperate the exits into urinary and rectal parts.