Lecture 4: digestive system Flashcards
the endodermal gut tube is formed
by body folding
epithelial tube is surrounded by..
splanchnic mesoderm
endoderm gives rise to the
epithelial cells of the gut tube (pharyngeal foregut, digestive system and respiratory system)
epithelial linning and glands of the digestive system
splanchnic mesoderm gives rise to
smooth muscle, connective tissue, blood vessels, visceral mesothelium
vitelline duct
communication between the midgut and the yolk sac
-this connection becomes the core of the umbilical cord
primordial gut is closed at
the ends of the oropharyngeal membrane and the cloacal membrane
bilayer dorsal mesentery
suspends the abdominal viscera in the body cavity
ventral mesentery
connects the stomach and liver to the ventral body wall
regions of the pharyngeal foregut
buccopharyngeal membrane to respiratory diverticulum
regions of the proper foregut
caudal to pharyngeal tube to superior duodenum (superior to ampulla of pancreatic duct)
regions of the midgut
inferior to bile duct/pancreatic duct to the junction of the right two-thirds and left third of the transverse colon
regions of the hindgut
left third of transverse colon to the cloacal membrane
derivatives of the foregut
- lower respiratory tract
- esophagus to duodenum (proximal to bile duct only)
- liver and biliary apparatys (hepatic ducts, gallbladder and bile duct), pancreas
- the artery of the foregut is the celiac trunk
derivatives of the midgut
- inferior duodenum to the right 2/3 of transverse colon
- the artery of the midgut is the superior mesenteric artery
derivatives of the hindgut
- left 1/3 of transverse colon to the rectum upper anal canal
- endoderm of the handgun also forms the epithelial lining of the bladder and urethra
- the artery of the hindgut is the inferior mesenteric artery
where does the esophagus develop
at the ventral wall of the foregut below the pharynx
esophageal muscle fiber of the upper 1/3
striated (muscular externa)
derived from myotomes
innervated by vagus nerve (CN X)
esophageal muscle fiber of the lower 2/3
smooth
derived from splanchnic mesenchyme
innervated by vagus nerve (CN X)
esophagotracheal septum
partitions the trachea from the esophagus
foregut development
- stomach rotates 90 degrees clockwise around the longitudinal axis
- rotation causes the duodenum to bend into a C shape and to the right
—- and —- become retroperitoneal
pancreas and duodenum
upper duodenum is —- and lower is —-
foregut and midgut
duodenum is supplied by
both the celiac artery and the superior mesenteric artery
hepatic diverticulum (liver bud) formation
endodermal thickening appears over ventral duodenum
septum transversum
location where the hepatic diverticulum grows
support stroma develop
from septum transversum and splanchnic mesoderm
hepatocytes and biliary apparatus derive from
endoderm
hepatic diverticulum divides into
- large cranial portion that will give rise to the primordial of the liver
- small ventral outgrowth of the bile duct that gives rise to the gallbladder and the cystic duct
hepatic diverticulum and the gut tube stay connected via
duct that will later become the bile duct
pancreas development
- initially a ventral and dorsal bud originating from endoderm of duodenum
- rotation of the gut tube moves ventral bud dorsally and both fuse
primitive umbilical ring
junction of embryonic ectoderm and the amnion
at week 5 which structures pass through the primitive umbilical ring
- connecting stalk with umbilical vessels
- yolk stalk (connects midgut to yolk sac)
- canal connecting intra and extra embryonic cavities
- wharton’s jelly (protects blood vessels)
- yolk sac is in the chorionic cavity
physiological herniation
intestinal loop enter the extra embryonic cavity during 6th week of development
physiological herniation is due to
- continued midgut elongation (growth of the small intestine is more rapid and greater than growth of the abdomen)
- rapid growth and expansion of the liver (abdominal cavity is too small for the organs)
development of the hindgut
-dorsal mesentery shortens and the descending colon becomes retroperitoneal
