128. GI Development/Organization Flashcards
What makes up the foregut, hindgut, and midgut?
What is the difference between lesser omentum and greater omentum?
Foregut: Upper GI foregut (oral cavity, oral pharynx, laryngopharynx), Abd Foregut (stomach, half duodenum)
Midgut: half duodenum, jejunum, ileum, cecum (+ appendix), ascending colon, 2/3 transverse colon
Hindgut: 1/3 transverse colon, descending colon, sigmoid colon, rectum
Omentum: fatty skin, stomach mesentery
Lesser omentum: lesser curve stomach to liver
Greater omentum: greater curve of stomach over intestines
What is a mesentery?
Where do parietal peritoneum and visceral peritoneum come from?
What is the architecture for artery, parasymp nerve, and ventral mesentery for each of the foregut, midgut and hindgut?
Mesentery: 2 layers of visceral peritoneum supporting gut tube, route for arteries/nerves
Parietal Peritoneum: somatopleure of lateral plate
Visceral Peritoneum: splanchnopleure of lateral plate
Foregut: celiac trunk, vagus n, present ventral mesentery
Midgut: SMA, vagus n, no mesentery
Hindgut: IMA, pelvic splanchnics (S2-S4), no mesentery
How does Meckel’s Diverticulum form?
What marks the free edge of the Ventral Mesentery?
How does the peritoneal cavity form during development?
Meckel’s: persistence of sinus, yolk sac remnant off distal ileum (may be fistula - opening to umbilicus; or cyst/fibrous cord)
Free edge of ventral mesentery marks boundary of foregut and midgut!
Breakdown of the midgut and hindgut’s ventral mesenteries leads to formation of the peritoneal cavity
How does the lesser sac form? Where is it?
What is the greater sac?
What is the name of the communication between greater and lesser sacs? Where is this?
Lesser sac: space behind stomach formed as dorsal mesogastrium bags out left as stomach rotates; grows down over small intestines
Greater sac: peritoneal cavity (bounded by parietal peritoneum)
Epiploic foramen of winslow: under free edge of lesser omentum
How does the midgut develop with SMA?
How does this relate to congenital diseases like omphalocele and gastroschisis?
Before W10: midgut grows into umbilical cord and LOOPS around SMA
W10: midgut returns to abd cavity
Omphalocele: congenital umbilical hernia of midgut (midgut intestines fail to return), COVERED BY AMNION (b/c still inside umbilical cord)
Gastroschisis: midgut hernia due to ventral wall defect, alongside umbilical cord, organs bathed by amniotic fluid
Retroperitoneal Organs:
Where do peritonealized organs develop?
What are the primary retroperitoneal organs?
What are the secondary retroperitoneal organs?
Peritonealized: organs develop in mesentery
Primary retro: superficial to parietal peritoneum (kidneys, aorta, IVC, rectum, bladder, vagina)
Secondary retro: get pushed against posterior abd wall and look retro (Ascending/Descending Colon, pancreas, duodenum)
