Anatomy Lecture 27_Development of Abdominal Organs

Question 1

What are the 4 developmental dorsal Mesenterys?

Answer 1

1) Dorsal Mesogastrium
2) Dorsal Mesodeuodnum
3) Mesentery Proper (this contains most of the small intestine)
4) Dorsal Mesocolon

Question 2

What is Esophageal atresia?

Answer 2

It is when the esophagus fails to Recanalize during week 8 of development. This leaves the espohagus in two parts with the proximal portion ending in a blind sac. This prevents the fetus from swallowing amniotic fluid which is essential for gut development

Question 3

Describe rotation of the developing stomach

Answer 3

1) the stomach rotates 90 degrees around the longitudinal axis. The side that was origionaly the posterior wall becomes the left wall and grows at a greater rate giving rise to the greater curvature of the stomach.
2) The stomach then rotates away from being totally logitudinal and tips the pyloric region to the right and the cardia to the left.

Question 4

What does the 90 degree logintudinal rotation of the stomach create?

Answer 4

It pulls the mesentary to the left and creates the lesser omental sac (omental bursa)

Question 5

What does the vertical rotation of the stomach give rise to?

Answer 5

As the stomach tips it takes the mesentery with it and this gives rise to the greater omentum.

Question 6

What does the spleen develop from?

Answer 6

It develops at week 5 of gestation within the dorsal mesogastrium from lateral plate mesoderm

Question 7

What two ligaments hold the spleen intraperatonial?

Answer 7

Fused to left kidney by splenorenal lig., stomach by gastrosplenic lig.

Question 8

What does the Ventral Mesogastrium turn into?

Answer 8

falciform ligament & lesser omentum

Question 9

Where do the two buds of the Pancreas arise?

Answer 9

Dorsal (dorsal mesogastrium) & Ventral (ventral mesogastrium). The dorsal bud is basically coming off the proximal duodenum. The ventral bud is coming off the bile duct.

Question 10

What causes the two buds of the Pancreas to fuse?

Answer 10

• Rotation of duodenum to right moves ventral bud dorsally
• Ventral bud fuses with dorsal bud
• Forms uncinate process & (part) head of pancreas
• Dorsal bud forms the rest

Question 11

What gives rise to the Main pancreatic duct?

Answer 11

distal dorsal duct and entire ventral duct

Question 12

What gives rise to the Accessory pancreatic duct?

Answer 12

proximal dorsal duct (sometime this structure is not present in adults)

Question 13

Describe an Annular Pancreas

Answer 13

An Annular Pancreas results when the ventral bud bifercates and fuses around the duodenum. This constricts the duodenum and will likely result in projectile vomiting. Typically this occurs above the pancreatic duct. This results in no billiouse vomit

Question 14

Describe the formation of the midgut

Answer 14

The mesnentery proper contains two contains two loops, the cephalic limb (gives rise to the small intestine and is located superior to the SMA) and the caudal limb (gives rise to the large intestine and is inferior to the SMA)

1) The cephalic limb experiences rapid growth and coils, the caudal limb does not
2) The loops rotate 90 degrees placing the cephalic limb on the right. The intestine then herniates into the umbilical cord (week 6)
3) At week 10 the intestinal loops return to the abdominal cavity. They then rotate 180 degrees more. This places the cephalic limb (small intestine) on the left and the caudal limb (large intestine) on the right

Question 15

Which structures are retroperitoneal?

Answer 15

Duodenum, Pancreas, asending and desending colon

Question 16

What is Ileal (Meckel) Diverticulosis?

Answer 16

• Portion of vitelline duct persists
• Forms a diverticulum of ileum
• Located ~2’ proximal to iliocecal valve

Question 17

What is Omphalocele

Answer 17

Failure of physiological umbilical herniation to return to abdomen

Question 18

Define Gastroschisis

Answer 18

• One or both lateral folds fail to move
ventrally
• Intestinal loops herniate directly
through wall & into amniotic cavity
• Corrosive effect to bowel and
compromised blood supply
(volvulus)
• Defect usually to the right of
umbilicus

Question 19

Describe the formation of the anal canal

Answer 19

1) the hind gut and allantois join at the Cloaca

2) the Urorectal septum lengthens & ruptures cloacal membrane giving rise to seperate anal & urogenital opening