5.4 Embryology of the GIT

Question 1

Which duct connects the primitive embryological gut to the yolk sac?

Answer 1

Vitelline duct (vitelline = yolk)

Question 2

What is a cloaca

Answer 2

Cavity for genitourinary/GIT secretions

Question 3

True or false: the mouth is blocked off during early gut development by the oropharyngeal membrane

Answer 3

True; there’s no nutrition coming in there, is there?

Question 4

At what week of embyronic development are the blood supplies of the foregut, midgut, and hindgut set?

Answer 4

Week 4 (the guts’ blood is ready to pour at week four)

Question 5

How is it that tracheoesophageal fistulas can form?

Answer 5

• The lungs and trachea originate from the foregut! Specifically, the foregut that becomes the oesophagus
• If the tracheoesophageal septum doesn’t separate the structures, a join (AKA fistula) can form.

Question 6

The stomach rotates __° _____wise during development

Answer 6

90° clockwise.

Question 7

Embryologically, why does the stomach have a greater/lesser curvature?

Answer 7

Grows more dorsally than ventrally; bulges outward like a kidney bean.

Question 8

What is another name for the lesser sac of the peritoneum?

Answer 8

The omental bursa.

Question 9

What other organs are moved into position during the developmental rotation of the stomach?

Answer 9

• Liver
• Spleen
• Pancreas

Question 10

Where is the border between the part of the duodenum that develops in the foregut vs midgut?

Answer 10

Just distal to the bile duct.

Question 11

Production of blood starts in week _ of development, and production of bile starts in week _.

Answer 11

Blood: 6
Bile: 12

Question 12

How many buds does the pancreas originally have? Why is the pancreas connected to the bile duct?

Answer 12

• Originally has two
• Ventral one is originally connected to bile duct; during rotation, it stays connected, even as it joins w the rest of the pancreas

Question 13

The midgut would be extremely long if we developed it one long line in the womb. How did mother nature solve this?

Answer 13

• Physiological hearniation
• Midgut rotates 90°, then 180°, pulling everything around (this is why the large intestine runs around the others; it’s turned in last)

Question 14

What duct separates the endoderm that becomes small vs large intestine? How does this affect growth rates?

Answer 14

• Vitelline duct
• Faster growth above (more intestine), slower growth below

Question 15

Meckel’s diverticulum results from incomplete retraction of the…

Answer 15

Vitelline duct

Question 16

True or false: the urethra arises from hindgut endoderm

Answer 16

True (!)

Question 17

What septum allows the cloaca to separate in to the rectum and urogenital system in humans? What is the surface anatomical landmark of this?

Answer 17

Urorectal septum. Surface anatomically, there is the perineum.