9 22 Embriology of the gut tube-Table 1 Flashcards
what is the GI tract largly made of
the endoderm
what does the endoderm contribute to in the GI?
the epithelial lining of the gut and the epithelial components of the glands
what does the mesoderm contribute to in the GI tract?
muslces, connective tissue, mesentaries and mesenchymal components of glands
what does the ectorderm contribute to?
epithelium of mouth and anus enteric gagnlia
what is the sheet of mesoderm that suspends the gut tube in the middle of the body tube?
the splanchnic mesoderm
what lines the primitive gut
the splanchnic mesoderm or the visceral serous membrane
what is derived from the visceral serous membrane and extends the lenght of the gut
the dorsal mesentery
what does the dorsal mesentery serve for?
the pathway for blood vessels, nerve and lymphatics suppling the GI kltract
what are the divisions of the GI tract?
the pharynx; respiratory diverticulum; stomach; liver cords; gall bladder; Midgut; hindgut
what provides blood to the stomach
the celiac artery
what provides blood to the intestine nearer the stomach
the superior mesenteric artery
what provides blood to the hindgut
the inferior mesenteric
the gut tube starts out hollow and the cells proliferate and fill the tube, how does it becoem a tube again?
the cells cavitate out again to form a larger but again hollow tube!
What can be a possible result of caviation of the gut that goes wrong?
diverticulus, or a stenosis (a small out growth or a narrowing.)
how can we get areas of the GI tract that undergo atresia
defective cavitation; malrotation can cuase twisting of the mesentaries, resulting in loss of blood supply and subsequent necrosis of the gut.
what is a mesontary
a connective layer of tissue from an organ to the walls of the cavity etc.
what is unique for the stomach mesoderm?
there is a ventral mesontary as well as the dorsal mesontary
how do we form the stomach
twisting of the tube about 90 degrees, and differential growth on one side of the tube
what is volvulus in the stomach
malrotation can result in this, portion of the stomach rotate abnormally, result in abnormal twisting.
what can volvulus lead to?
lead to obstruction due to twisting of GI tube, and ischemia due to twisting of the mesenteries and interruption of the blood supply
how can malpositioning of the stomach and other organs occur?
from malrotation.
if there is a heterotaxia patient what else would you look for?
vascular anomalies
what is complete reversal of the left and right sidedness of the organs
Situs Inversus
what is partial reversal of the left right orientation of the organs?
heterotaxia
organs enclosed in a double layer of peritoneum that connect them to the body wall
intraperitoneal
Organs that are not suspended in mesenteries, but lie agains tthe posterior body wall covered by a single layer of peritoneum
Retroperitoneal
organs that are intially intraperitoneal and beome retroperitoneal later on due to fusion of hte mesenteries with the posterior wall of the peritoneum
secondarily retroperitoneal
Intraperitoneal organs
stomach, transverse colon, small intestines, sigmoid colon
Retroperitoneal organs
Thoracic esophagus; rectum
Secondarily retroperitoneal organs
duodenum; pancreas; ascending colon; descending colon
what is the area of the liver that impacts the diaphram and has no fascia between them
the bare area of the liver
Nkx2, Barx1 and Hox11 all affect what?
the spleen and other l/R asymmetric organs early in development.
Describe the formation of the pancreus
formation of a dorsal and ventral pancreus, and the ventral will rotate around and drag the hepatic duct with it, and combine with the dorsal pancreatic bud. and make a common duct out.
spleen
formed entirely form the dorsal mesogastrium; moves to the the left side as a consequence of stomach rotation
what is the early and later on purpose of the spleen
early it is a hemotopoietic organ, but later it is just for lymphatics
describe the midgut development!
The midgut herniates to the umbilicus and rotates 90 degrees counter clockwise while doing this. The midgut is then retracted later and does another 180 degree counter clockwise rotation.
what does the midgut contribute to?
no adult organs or glands associated with the midgut.
what if only the first 90 degree rotation of the midgut happens
then the colon is left out by itself on the left hand side!
what if the first rotation in clockwise and no second rotation?
then it looks normal but the duodenum and small intestine traverses over the top of the colon instead of the other way around.
what is omphalocele?
where the midgut does not retract and is left in the umbilicus region with amniotic membrane around them
Prognosis of omphalocele
can be surgically corrected but look for genetic abnormailites
Vitelline connection
the connection to the umbilicus form the ileum.
a small diversion of the intestine towards a ligament connected to the umbilicus
meckel’s diverticulum; it is usually asymptomatic
small cysts or fistulae from the umbilicus to the intestine that can be painful or infected
vetellin cysts
the caudal portion of the gut tube
the cloaca
continuous with the allantois
cloaca
partition the cloaca to the rectum and urogenital sinus
the urorectal septum
rupture of the cloacal membrane creates:
the urogenital sinus and the rectum
how to form the anal canal
by cavitation of the ectodermal anal pit, fuses to the rectum at the pectinate line
possible problems with the cloaca forming the anus properly
urorectal fistula or rectovaginal fistula where the colon connects to the urethra or vagina;;; rectoperineal fistula where colon connects to the wrong spot in the skin. or the anal membrane doesn’t rupture and no real anus.
what embrio layer contributes to the formation of the end of the gut tube?
the ectoderm at the anus.
