Week 5 Flashcards
When is the primitive gut tube formed, and from what?
Body folding during week 4; from the top of the yolk sac
Also, during this time, the body cavity and anterolateral body wall are formed and the amnion encases the embryo
Which germ layer forms the epithelial lining of the gut tube?
endoderm
Which germ layer forms all other layers of the gut tube wall (except nerves and ganglia)?
mesoderm
What germ layer forms the serous membrane of the abdomen (peritoneum)?
mesoderm
What is a mesentery?
a double layer of peritoneum reflecting from the abdominal wall to enclose the viscera
What forms the boundaries of foregut, midgut, and hindgut?
The 3 arteries that branch off the anterior aorta: celiac trunk, superior mesenteric artery (SMA), and inferior mesenteric artery (IMA)
Liver buds
buds off the foregut into the ventral mesentery dividing it into the falciform ligament and the lesser omentum
What is septum transversum?
The mesoderm that the liver buds into; it forms the CT and blood vessels of the liver and also forms the diaphragm
Pancreas buds
off the foregut just above the midgut junction and has 2 buds: dorsal pancreas that buds into dorsal mesentery and ventral pancreas that buds into ventral mesentery
Stomach rotation in embryo development
it rotates 90 degrees clockwise on its longitudinal axis so the left side faces anteriorly
When the stomach rotates 90 degrees clockwise…
the dorsal mesentery of the stomach becomes the greater omentum, the liver moves to the right side of the abdomen and pushes the duodenum, pancreas, and part of the dorsal mesentery against the posterior body wall
Stomach growth and rotation creates the omental bursa or lesser peritoneal sac
spleen develops
from the mesoderm in the dorsal mesentery of the stomach. This makes the spleen a unique organ because it’s not derived from endoderm
Retroperitoneal organs
pancreas, most of the duodenum, ascending and descending colon, abdominal aorta, IVC
What are the names of the parts of the dorsal mesentery of the stomach that don’t fuse with the parietal peritoneum covering the posterior body wall?
splenorenal ligament, gastrosplenic ligament, and greater omentum
biliary duct system and gallbladder are formed from what?
the liver bud (hepatic diverticulum)
Physiological herniation
rapid growth of the midgut causes it to loop into the umbilical cord, where is it still connected to the rapidly resorbing yolk sac by the yolk stalk
Cranial limb of the midgut loop forms
the jenunum and upper ileum
the caudal limb of the midgut loop forms
the lower ileum through the proximal 2/3 of the transverse colon
Midgut loop rotation
by 10 weeks the midgut loop has rotated 270 degrees around the axis of the SMA
Order of organs returning to body cavity after physiological herniation
jejunum returns first, to the left side and then ileum to the right side. Cecum returns last, initially to the RUQ, but then moves dow the the RLQ
In rotation of the midgut, what happens to the mesenteries of the ascending and descending colon?
the mesenteries fuse with the posterior abdominal wall, so they become retroperitoneal
Transverse mesocolon fuses with
the greater omentum as the greater omentum passes anterior to it
What is mesentery proper
the mesentery of the small intestine
pyloric stenosis
results from hypertrophy of the muscularis externa of the pylorus, obstructing the pyloric canal and causing forceful (projectile) nonbilious vomiting
Etiology unclear, but may be multifactorial from both genetic and environmental factors. Symptoms usually begin 3-5 weeks of age