GI Tract Development Flashcards
what is the lining from the oro-pharynx to the anal canal?
epithelium derived from endoderm
what is the epithelial tube surrounded by?
splanchnic mesoderm
what does splanchnic mesoderm form?
forms the muscle and connective tissue layers, blood vessels and peritoneal components (mesothelium and connective tissue)
primitive gut tube formatin
folding results in a portion of the endoderm lined yolk sac to be incorporated into the embryo as the primitive gut tube
endoderm derivatives
rise to the epithelial cells of the gut tube
-pharyngeal foregut, digestive system, and respiratory system
splanchnic mesoderm derivatives
smooth muscle, connective tissue, blood vessels, visceral epithelium
how does the midgut communicate with the yolk sac?
via the vitelline duct which becomes the core of the umbilical cord
dorsal mesentary
it is bi-layered and suspends the abdominal viscera in the body cavity (intraembryonic body cavity)
ventral mesentary
connects stomach and liver to the ventral body wall
how is the primordial gut closed?
by the ends of the oropharyngeal membrane and the cloacal membrane
artery of the foregut
celiac trunk
foregut range
pharyngeal - buccophaaryngeal membrane to respiratory diverticulum
proper- caudal to pharyngeal tube to superior duodenum and superior to ampulla of the pancreatic duct
midgut artery
superior mesenteric artery
- inferior duedenum and RIGHT 2/3 of the transverse colon
midgut range
inferior to the bile duct/pancreatic duct to the junction of the right 2/3 and left third of the transverse colon
hindgut artery
inferior mesenteric artery - left one third of the transverse colon to the rectum upper anal canal
hindgut range
left third of the transverse colon to the cloacal membrane
esophagus development
develops at the ventral wall of the foregut, below the pharynx and elongates rapidly due to the descent of the heart and lungs
upper 1/3 of esophagus
muscle fibers are derived from myotomes and is striated muscularis externa
lower 2/3 of esophagus
muscle fibers are smooth muscle and derived from the splanchnic mesoderm mesencyme
esophagotracheal septum
partitions the trachea from the esophagus
foregut/stomach rotation how/endpoint and what causes it
stomach rotates 90 degrees clockwise around the longitudinal axis
- differential growth
- creates the greater and lesser curvature of the stomach
what do the stomach rotations do to the duodenum?
bend it into a C shape and displace it to the right and most of it becomes secondarily retroperitoneal (adhered to body wall)
blood supply (artery) to the duodenum
celiac artery and the superior mesenteric artery
upper = foregut
lower = midgut
what happens to pancreas when stomach rotates and where is it derived
also becomes put into a retro-peritoneal position with the duodenum and it is derived from endoderm
hepatic diverticulum
initial growth of the liver and gall bladder
from an endodermal thickening on the ventral aspect of the duodenum
what does the hepatic diverticulum grow into?
septum transversum
2 divisions of the hepatic diverticulum
- larger cranial portion gives rise to the PRIMORDIAL OF THE LIVER and a connection of the diverticulum and gut tube maintained becomes the bile duct
- a smaller, ventral outgrowth of the BILE duct gives rise to the gallbladder and the cystic duct
bile duct
recieves from hepatic duct from liver and also cystic duct from the gallbladder
gallbladder
ventral outgrowth of the bile duct that will also give rise to the cystic duct
pancreas
initially a ventral and dorsal bud originating from the endoderm of the duodenum. when the gut rotation occurs it brings the ventral bud to the left and dorsal and FUSION occurs. the common bile duct will also move dorsal
what junction marks end of foregut and beginning of midgut?
JUCNTION OF THE PANCREATIC DUCT AND THE COMMON BILE DUCT - both emptying into the duodenum
main pancreatic duct
main duct of ventral bud and distal part of the duct of the dorsal bud
VENTRAL =MAIN
accessory pancreatic duct
proximal part of the dorsal bud that regresses can remain as the accessory pancreatic duct
primitive umbilical ring
junction of embryonic ectoderm and the amnion
At week 5 what structures pass through the primitive umbilical ring?
- connecting stalk with umbilical vessels
- yolk stalk (connects midgut and yolk sac)
- canal connecting intra and extraembryonic cavities
- wharton’s jelly - protects blood vessels (extracellular support)
- yolk sac is in the chorionic cavity
yolk stalk
connects the midgut and yolk sac
major event in development of midgut (when and what)
physiological HERNIATION of the midgut around WEEK 6. the intestinal loops enter the extraembryonic cavity
what causes the midgut/ umbilical herniation?
continued midgut elongation (growth of the small intestine is more rapid and greater than the growth of the abdomen
there is also rapid growth and expansion of the liver (abdominal cavity at this stage is too small for all the organs
hindgut gives rise to what structures
left 1/3 of the transverse colon descending colon sigmoid colon rectum upper anal canal
the endoderm of the hindgut also forms the…
epithelial lining of the bladder and urethre
how does the descending colon become retroperitoneal?
the dorsal mesentary SHORTENS
stroma of liver and gall bladder
septum transversum and splanchnic mesoderm
