Development of the GI Tract

Question 1

Describe the formation of the primitive gut tube.

Answer 1

The gut tube is formed from the endoderm lining the yolk sac which is then enveloped splanchnic mesoderm which is wrapped around the gut tube to form the mesenteries that suspend the gut tube within the body cavity. The mesoderm immediately associated with the endodermal tube also contributes to most of the wall of the gut tube, which is it’s self surrounded by the developing coelom as the result of cranial and caudal folding.

Question 2

Name the 3 embryonic divisions of the gut.

Answer 2

1. Foregut
2. Midgut
3. Hindgut

Question 3

What is the medical term given to the embryonic future mouth?

Answer 3

Stomatodeum

Question 4

What is the medical term given to the embryonic future anus?

Answer 4

Proctodeum

Question 5

What does the foregut derive into in adults?

Answer 5

• Oesophagus
• Stomach
• Pancreas
• Liver and gall bladder
• Duodenum (Proximal to entrance of bile duct)

Question 6

What does the midgut derive into in adults?

Answer 6

• Duodenum (Distal to entrance of bile ducts)
• Jejunum
• Ileum
• Cecum
• Ascending colon
• Proximal 2/3 transverse colon

Question 7

What does the hindgut derive into in adults?

Answer 7

• Distal 1/3 transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Upper anal canal
• Internal lining of bladder and urethra

Question 8

What is the arterial blood supply to the foregut?

Answer 8

Celiac trunk

Question 9

What is the arterial blood supply to the midgut?

Answer 9

Superior mesenteric artery

Question 10

What is the arterial blood supply to the hindgut?

Answer 10

Inferior mesenteric artery

Question 11

Name the 5 branches of the abdominal aorta from cranial to cephalic.

Answer 11

• Celiac trunk
• Superior mesenteric artery
• Renal artery
• Gondal artery
• Inferior mesenteric artery

Question 12

Name 2 organs of the gastrointestinal system that have mixed blood supply and name their supplies.

Answer 12

1. Duodenum: The proximal portion until the entry of the bile duct is supplied by the celiac trunk, the distal portion to the entry of the bile duct is supplied by the superior mesenteric artery.
2. Pancreas: The superior pancreaticoduodenal is supplied by the celiac trunk, whereas the inferior pancreaticoduodenal is supplied by the superior mesenteric artery.

Question 13

Describe the development of the intraembryonic coelom.

Answer 13

It begins as one large cavity. It is later divided by the future diaphragm into the abdominal and thoracic cavities.

Question 14

In which region(s) of the gut tube does the dorsal mesentery provide suspension?

Answer 14

The foregut, midgut and the hindgut

Question 15

In which region(s) of the gut tube does the ventral mesentery provide suspension?

Answer 15

The foregut only

Question 16

What is the ‘free edge’?

Answer 16

Where the ventral mesentery finishes

Question 17

Which sac is known as the greater sac?

Answer 17

Left

Question 18

Which sac is known as the lesser sac?

Answer 18

Right

Question 19

Which mesentery, dorsal or ventral, forms the greater omentum?

Answer 19

Dorsal

Question 20

Which mesentery, dorsal or ventral, forms the lesser omentum?

Answer 20

Ventral

Question 21

Where is the lesser sac situated, in-front or behind the stomach?

Answer 21

Behind

Question 22

How are the omenta and the greater and lesser sacs formed?

Answer 22

Rotation of the stomach

Question 23

Name 2 secondarily retroperitoneal organs.

Answer 23

1. Duodenum

2. Pancreas

Question 24

Describe how the trachea and oesophagus form from the foregut.

Answer 24

A respiratory diverticulum forms in the ventral wall of the foregut at the junction with the pharyngeal duct.

A tracheoesophageal septum then forms.

Question 25

Name glands formed in the ventral mesentery.

Answer 25

• Liver

- Biliary system

Question 26

Name glands formed in the dorsal mesentery.

Answer 26

• Spleen

- Pancreas