Gut Rotation

Question 1

What 3 germ layers are made due to cranial-caudal folding?

Answer 1

Mesoderm, Ectoderm, Endoderm.

Question 2

Developmentally, what separates the abdominal cavity?

Answer 2

Septum transversum and pleuroperitoneal membrane.

Question 3

From what type of mesoderm does the parietal layer of peritoneum arise?

Answer 3

Somatic mesoderm.

Question 4

From what type of mesoderm does the visceral layer of peritoneum arise?

Answer 4

Splanchnic mesoderm.

Question 5

How many layers and between which structures, are the peritoneal layers of the mesentery and omentum?

Answer 5

Mesentery: 2 peritoneal layers between organ and body wall
Omentum: 2 peritoneal layers between 2 organs

Question 6

What organs make up the foregut?

Answer 6

Stomach, duodenum, liver, gallbladder, pancreas.

Question 7

What organs make up the midgut?

Answer 7

Jejunum, ileum, cecum, appendix, ascending colon, first 2/3 transverse colon

Question 8

What organs make up the hindgut?

Answer 8

Last 11/3 transverse colon, descending colon, sigmoid colon, rectum

Question 9

Which organ is primary retroperitoneal?

Answer 9

Rectum.

Question 10

Which organs are secondary retropertioneal?

Answer 10

Duodenum, pancreas, ascending colon, and descending colon

Question 11

What role does Wnt-5a and Hox expression play in the primitive devlopment of the foregut and hindgut?

Answer 11

Initially, the gut tube is supposed to be the hindgut due to Wnt-5a signaling. But, Wnt antagonists repress hindgut identity in the cranial section of the gut tube. Transcription factors (Hhex, Sox2, Foxa2) then allow it to have a foregut identity. Cdx2 and Pdx1 cause Hox expression in the midgut –> hindgut and this makes the divisions of the small and large intestine and sphincters at the junctions

Question 12

How is the lesser sac/omental bursa formed?

Answer 12

This occurs through rotation of the stomach. Barx1 gene causes dilation of the dorsal part of the foregut –> 90 degree rotation with duodenum = rotation of dorsal mesogastrium (lesser omentum) that is attached to liver == lesser sac/omental bursa behind stomach. Lesser omentum connects liver to stomach and liver is pulled to right side.

Question 13

What is congenital pyloric stenosis?

Answer 13

This is hypertrophy of the pyloric sphincter which causes food to get backed up into the stomach and causes vomiting.

Question 14

How is the liver developed?

Answer 14

hepatic/liver bud off foregut into –> septum transversum –pushed of –> peritoneum. Part not totally pushed out = bare area. Ventral mesentery = falciform ligament that connects liver to anterior abdominal wall. Hepatoduodenal ligament connects liver to duodenum and contains the portal triad.

Question 15

How is the gallbladder formed?

Answer 15

Liver bud –> Cystic diverticulum –> gallbladder

Question 16

How is the cystic duct formed?

Answer 16

Liver bud –> Cystic diverticulum –> cystic duct

Question 17

How is the pancreas formed?

Answer 17

1) Liver bud –> Cystic diverticulum –> Ventral pancreatic bud
2) Dorsal duodenum –> Dorsal pancreatic bud
3) Ventral bud rotates around duodenum and meets dorsal bud and then fuse = uncinate process

Question 18

How is the common bile duct formed?

Answer 18

Shared stalk of the liver and gallbladder –> common bile duct

Question 19

The duct of which part of the pancreas forms the main pancreatic duct? What happens to the other part?

Answer 19

The ventral pancreas. The dorsal pancreas duct regresses or makes accessory pancreatic duct

Question 20

Why is the spleen a mesodermal condensation and not an outgrowth of the gut tube?

Answer 20

The dorsal mesogastrium condenses to form the lienorenal and gastrolienal ligaments. This condensation allows for the spleen to mature. Spleen = mesodermal condensation?

Question 21

How are the intestines formed?

Answer 21

Cecum swells on intestinal loop –> loop rotates 90 degress counterclockwise –> small intestine herniates through umbilical opening –> body cavity grows –> small intestine re-enter abdominal cavity and push descending colon to left side and cecum and ascending colon to right side

Question 22

Which structure is the mesogastrium initially? And what does it become?

Answer 22

Lesser omentum/omental bursa. It becomes the greater ommentum.

Question 23

Why does the small intestine herniate through the umbilical opening during the development of the intestines?

Answer 23

Because the gut tube grows faster than the fetus can contain.

Question 24

What is Omphalocele?

Answer 24

Failure of midgut to return to abdominal cavity after herniation.

Question 25

What is Umbilical Hernia?

Answer 25

Failure of anterior abdominal muscles to join at the midline linea alba.

Question 26

What condition involves the failure of the vitelline duct and yolk sac to degenerate and remain attached at the umbilicus?

Answer 26

Meckel’s Diverticulum.

Question 27

What condition is characterized by the open connection between the intestinal lumen and outside via the umbilicus?

Answer 27

Umbilicoileal Fistula.

Question 28

What is Nonrotation?

Answer 28

When the gut loops fail to complete the final 180 degrees –> small and large intestine lie side by side

Question 29

What is the condition is characterized by the rotation of the midgut clockwise, instead of counter-clockwise?

Answer 29

Reverse Rotation.

Question 30

What is the cloaca?

Answer 30

It is the common opening for the hindgut and allantois

Question 31

How is the hindgut formed?

Answer 31

hindgut –> anorectal canal and allantois –> urogenital sinus and they –separated by–> urorectal septum expansion –fuses with–> proctodeum –> urogenital and anal membranes (from cloacal membrane)

Question 32

What is the anal pit?

Answer 32

An ectodermal invagination into anorectal canal.

Question 33

What is the pectinate line in the adult?

Answer 33

The boundary between the ectodermal and the endodermal derived tissue within anal canal