Abdomen Development I

Question 1

What produces the primitive endodermal gut tube

Answer 1

Cranial-caudal and lateral folding of yolk sac; outlet via yolk stalk (future umbilical cord)

Question 2

What does the splanchnic mesoderm turn into?

Answer 2

Muscles, connective tissue, and other layers of gut and gut-derived abdominal organs

Question 3

What does the ectoderm produce?

Answer 3

produces stomadeum and proctodeum

Question 4

What separates the foregut from stomadeum?

Answer 4

Oropharyngeal membrane – ruptures around 4 weeks,

Allows fetal swallowing of amniotic fluid

Question 5

What’s the cloacal membrane?

Answer 5

Separates hindgut from future proctodeum

Ruptures around 8 weeks (called anal membrane at that point), allows passage of amniotic fluid through digestive system

Question 6

What does the falsiform ligament derived from?

Answer 6

Ventral mesentary

Question 7

Intraperitoneal?

Answer 7

Surrounded by its own visceral peritoneal

Question 8

List the intraperitoneal organs

Answer 8

Stomach, Liver, Transverse colon, Jejunum, Ileum, Abdominal esophagus
Cecum, Sigmoid colon, Spleen, gall bladder, bile duct

Question 9

Failures of recanalization result in what?

Answer 9

Atresias (blockage) or stenosis (narrowing)

Question 10

What is mesentary formed from?

Answer 10

Double layer of peritoneum

Developed from mesoderm

Question 11

What divides the body into rt and left halves?

Answer 11

Dorsal and ventral mesentary

Question 12

Which lobes of the developing pancreas turn into head/tail?

Answer 12

Ventral – head

Dorsal – tail

Question 13

The ventral mesentary degrades, but persists as what?

Answer 13

Falsiform ligament
Lesser omentum
Mesentery of liver

Question 14

Polyhydramnios

Answer 14

Fetus can’t drink in amniotic fluid due to atresia

Question 15

What is the foregut?

Answer 15

Pharynx, esophagus, stomach, and proximal 1/3 of duodenum
Outgrowths: pharyngeal pouches, lower respiratory system, liver, pancreas, gallbladder
Celiac trunk provides everything except for those things outside of abdominal cavity

Question 16

What is the midgut?

Answer 16

Small intestine, cecum, appendix, ascending colon, proximal 2/3rds of transverse colon (to left colic/splenic flexure)
Arterial supply: SMA

Question 17

What is hindgut?

Answer 17

Distal 1/3 of ransverse colon, descending colon, sigmoid colon, rectum, superior portion of anal canal

Question 18

Which curve of the stomach grows faster – dorsal or ventral?

Answer 18

Dorsal – becomes greater curvature

Question 19

Which vagus nerve is posterior?

Answer 19

Right vagus is dorsal, left is ventral; everything moved 90 degrees clockwise!

Question 20

How many layers of peritoneum is omentum?

Answer 20

4 layers of peritoneum, 2 layers of mesentery

Question 21

What is the epiploic/omental formamen?

Answer 21

The entry into the lesser peritoneal sac/omental bursa (behind stomach)

Question 22

Where does the forgut end?

Answer 22

Distal to origin of common bile duct (proximal 1/3 of duodenum)

Question 23

Which pancreatic ducts are from which lobes?

Answer 23

Pancreatic duct – from ventral lobe of pancreas (head)

Accessory pancreatic duct – from dorsal lobe (tail)

Question 24

What is the spleen derived from?

Answer 24

Splanchnic mesoderm in dorsal mesenery of stomach

Question 25

How many rotations does the midgut go through?

Answer 25

3 counterclockwise rotation, as opposed to forgut (1 clockwise rotation)
Rotation 1: midgut loop rotates 90 degrees CCL
Rotation 2 and 3: small intestines start settling in, then large intestines enter
Finally, cecum descends to lower right position

The rotations press several organs against the posterior body wall, where they then become SRP

Question 26

Errors in development of midgut:

Answer 26

volvulus (intestines twist around eachother, blocks passage)

Incomplete rotation

Question 27

Outgrowths of the hindgut:

Answer 27

bladder and most of urethra

Question 28

What’s the cloaca?

Answer 28

Splits and forms urogenital membrane and anal membrane