Lecture 2 - Development of the Gut

Question 1

Vitelline duct

Answer 1

Connects the gut tube to the yolk sac. Should disappear with the yolk sac when the gut tube is internalized.

Question 2

Epithelial Plug

• atresia
• stenosis

Answer 2

Basically when the gut tube is being formed it gets plugged up on occasion by epithelial cells. Then apoptosis occurs in order to create the gut tube again. Atresia occurs when the gut tube can not recanalize. You can also have a stenosis where the canal becomes too narrow.

Question 3

Gastrochisis

Answer 3

When the lateral folding of the mesoderm doesn’t fuse properly. This causes the abdoment to be open to the environment and you will see parts of the intestines outside of the abdomen.

Question 4

Vitaline fistula

Answer 4

When the vitaline duct doesn’t disappear. There is still a connection between the gut and yolk sac.

Question 5

Merkel’s Diverticulum

Answer 5

A small, proximal, part of the vitaline duct doesn’t disappear, causing a small outgrowth on the intestines.

Question 6

What is in foregut? midgut? hindgut?

Answer 6

foregut - esophagus, stomach, duodenum (celiac trunk)
midgut - duodenum, jejunum, ileum, cecum, appendix, ascending colon, transverse colon (sup. mesenteric)
hindgut - transverse colon, descending colon, sigmoid colon, rectum (inf. mesenteric)

Question 7

retroperitoneal organ vs. peritoneal organ

Answer 7

retro - only partially covered by peritoneum. Covered by parietal peritoneum
peritoneal - entirely covered by peritoneum. Covered by visceral peritoneum.

Question 8

mesentery

Answer 8

connects parietal to ventral peritoneum.

Question 9

Hepatic diverticulum

Answer 9

small outgrowth in the ventral mesentary. It will turn into the liver and gall bladder. Connecting it to the duodenum will be the lesser omentum with the bile duct going through it. Connecting it to the body wall will be the falciform ligament.

Question 10

Pancreas

Answer 10

Has a dorsal and a ventral bud. The ventral bud ends up swinging around to the dorsal side. They become the pancreas. The two end up fusing. The ventral portion is the lower head of the pancreas and is connected to the major duct. The dorsal portion is the upper head, neck, body, and tail and will have the minor duct.

Question 11

Annular pancreas

Answer 11

Sometimes instead the ventral portion swining over, both sides split and meet to fuse. When this happens it can be problematic because they will fuse around the duodenum and potentially make it difficult to pass food. Therefore, you can begin to vomit.

Question 12

Spleen

Answer 12

Begins from a bundle of cells in the dorsal mesentery. The gastrosplenic ligamet connects the spleen to stomach. The splenorenal ligament connects it to the kidney as well as the body wall. The splenic artery should run in the splenorenal ligament.

Question 13

Fusion fascia

Answer 13

When the gut tube loses its ventral mesentery it is free to rotate. It ends up rotating to the left and fuses to the body wall. Because there is a fusion, it loses the epithelial cells in it and it is no longer called peritoneum. This causes the gut to be secondarily retroperitoneal.

Question 14

Make sure to know what it primary retroperitoneal, secondary retroperitoneal, and peritoneal

Answer 14

Slide 36

Question 15

Foregut rotation

- epiploic foramen of Winslow

Answer 15

Foregut undergoes a 90 degree rotation, putting the liver on the right and the spleen on the left. When this happens, it creates the epiploic foramen of Winslow on the right side of the body behind the lesser omentum.

Question 16

Which layer does the yolk sac and amniotic cavity come from?

Answer 16

yolk sac = endoderm

amniotic cavity = ectoderm

Question 17

Midgut rotation

Answer 17

The midgut develops an intestinal loop which herniates out of the umbilicus during the 6th week. While in the umbilical cord and during retraction, the intestines undergo a 270 degree turn. This is why the jejunum is on the left and ileum is on the right. Also why the colon makes a “U” shape.

Question 18

Omphalocele

Answer 18

Failure of the intestinal loop to retract back into the abdomen. It will look smaller than the Gastrochisis because it is separated from the amniotic cavity and in the umbilical cord.

Question 19

Where does the splenic artery run?

Answer 19

In the splenorenal ligament