Gut Rotation Flashcards
What 3 germ layers are made due to cranial-caudal folding?
Mesoderm, Ectoderm, Endoderm.
Developmentally, what separates the abdominal cavity?
Septum transversum and pleuroperitoneal membrane.
From what type of mesoderm does the parietal layer of peritoneum arise?
Somatic mesoderm.
From what type of mesoderm does the visceral layer of peritoneum arise?
Splanchnic mesoderm.
How many layers and between which structures, are the peritoneal layers of the mesentery and omentum?
Mesentery: 2 peritoneal layers between organ and body wall
Omentum: 2 peritoneal layers between 2 organs
What organs make up the foregut?
Stomach, duodenum, liver, gallbladder, pancreas.
What organs make up the midgut?
Jejunum, ileum, cecum, appendix, ascending colon, first 2/3 transverse colon
What organs make up the hindgut?
Last 11/3 transverse colon, descending colon, sigmoid colon, rectum
Which organ is primary retroperitoneal?
Rectum.
Which organs are secondary retropertioneal?
Duodenum, pancreas, ascending colon, and descending colon
What role does Wnt-5a and Hox expression play in the primitive devlopment of the foregut and hindgut?
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
How is the lesser sac/omental bursa formed?
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.
What is congenital pyloric stenosis?
This is hypertrophy of the pyloric sphincter which causes food to get backed up into the stomach and causes vomiting.
How is the liver developed?
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.
How is the gallbladder formed?
Liver bud –> Cystic diverticulum –> gallbladder
How is the cystic duct formed?
Liver bud –> Cystic diverticulum –> cystic duct
How is the pancreas formed?
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
How is the common bile duct formed?
Shared stalk of the liver and gallbladder –> common bile duct
The duct of which part of the pancreas forms the main pancreatic duct? What happens to the other part?
The ventral pancreas. The dorsal pancreas duct regresses or makes accessory pancreatic duct
Why is the spleen a mesodermal condensation and not an outgrowth of the gut tube?
The dorsal mesogastrium condenses to form the lienorenal and gastrolienal ligaments. This condensation allows for the spleen to mature. Spleen = mesodermal condensation?
How are the intestines formed?
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
Which structure is the mesogastrium initially? And what does it become?
Lesser omentum/omental bursa. It becomes the greater ommentum.
Why does the small intestine herniate through the umbilical opening during the development of the intestines?
Because the gut tube grows faster than the fetus can contain.
What is Omphalocele?
Failure of midgut to return to abdominal cavity after herniation.
What is Umbilical Hernia?
Failure of anterior abdominal muscles to join at the midline linea alba.
What condition involves the failure of the vitelline duct and yolk sac to degenerate and remain attached at the umbilicus?
Meckel’s Diverticulum.
What condition is characterized by the open connection between the intestinal lumen and outside via the umbilicus?
Umbilicoileal Fistula.
What is Nonrotation?
When the gut loops fail to complete the final 180 degrees –> small and large intestine lie side by side
What is the condition is characterized by the rotation of the midgut clockwise, instead of counter-clockwise?
Reverse Rotation.
What is the cloaca?
It is the common opening for the hindgut and allantois
How is the hindgut formed?
hindgut –> anorectal canal and allantois –> urogenital sinus and they –separated by–> urorectal septum expansion –fuses with–> proctodeum –> urogenital and anal membranes (from cloacal membrane)
What is the anal pit?
An ectodermal invagination into anorectal canal.
What is the pectinate line in the adult?
The boundary between the ectodermal and the endodermal derived tissue within anal canal
