Development of the Digestive System Flashcards
What is the name of the tube formed from the curvature of the embryo with the endoermal lining of the yolk sac?
what is the major feature that is different from a fully developed fetus?
primitive gut
it is sealed at both ends
What closes the primitive gut on the caudal end?
cranial end?
What is the name of the depression surrounding each of these structures
cloacal membrane (proctodium)
oralpharyngeal membrane (stomodium)
Which arteries primarily supply the foregut, midgut, and hindgut?
foregut: celiac artery
midgut: superior mesenteric artery
inferior mesenteric artery: hindgut
What surrounds the endodermal lining of the primitive gut?
What structure forms the mesentary?
splanchnic mesoderm
mesoderm also suspends he primitive gut from the body wall as mesentery
What 3 structures come from the transverse septum?
liver, ventral mesentery, and diaphragm
Identify the indicated features of the fetus
Identify the sections of the dorsal mesentery
The ventral mesentary always moves with which organ?
liver
How does the relationship between the stomach and the vagus nerves shift through development?
initially, the vagus nerves are lateral to the stomach, but as the stomach shifts from a cranial/caudal perspective to a more horizonal position, the vagus nerves shift to dosal and ventral to the stomach
What are the 3 phases to the development of the stomach?
What are the major effects of this rearrangement?
- localized dilation of the foregut
- rotation in transverse plane (anterior rotates over)
- rotaion in frontal plane (piloric end moves supriorly and to the right
rearranges the 2 mesentary
dorsal: omental bursa (greater omentum)
ventral: lesser omentum (Hepatoduodenal Ligament)
What impact does the rotation of the stomach have on the shape of the duodemum
The duodenum marks the beginning of what strucuture?
The rotation fo the stomach, combine with lesser rotation of the duodenum, produces the C-shape of the duodenum adn displaces the duodenum to the right and dorsad
small intestine (boundary between foregut and midgut)
Why is the liver considered a composite organ?
it is made up of endodermal cells from the proximal duodenal wall (by way of hepatic diverticulum) that invades and combines with mesodermal cells from the septum transversum
identify the aspects of the ventral messentary that are segmented by the expansion of the liver
Expansion fothe liver subdivides the ventral mesentary into Falciform Ligament, Lesser Omentum, and Hepatogastric Ligament
Where the liver abuts the diaphragm you get a “bare area”
Identify the indicated features of the developing pancreas
The major papilla forms from the (rotated) ventral bud; the ventral bud and hepatic deiverticulum form the main pancreatic duct, which also drains most of the dorsal bud
What is different about the spleen development as compared to other abdominal organs?
it has not adult or embryonic connection to the primitive gut
develops as a mesodermal proliferation in the dorsal mesentery that is secondarily invaded by vscular tissue
What are the 3 major steps in development of the midgut?
- Formation of Primary Intestinal Loop (PIL)
- PIL rotates 90 degrees adn pushes into hte umbilical cord (physiloogicla Herniation) – week 6
- PIL elongates (especially cephalic) and is retracted into the body cavity… durign the retraction the PIL rotates another 180 degrees … week 10
What makes up the cephalic limb?
The Caudal limb?
- cephalic limb:
- duodenum
- ileum
- Caudal Limb
- distal ileum
- transverse colon
axis of rotation is the vitelline duct (yolk sac) and superior mesenteric artery
What part of the midgut retracts frist? How is its movement different?
the jejunum retracts frist and moves to the left side
the rest of the small intestine retracts to the right
last to retract is the cecal bud, which moves to the upper right quadrant; cecum will descend to the lower right as the appendix develops
List the portions of the digestive system that fall into the following categories:
Retroperitoneal viscera
secondarily retroperitoneal viscera
- Reroperitoneal viscera
- Esophagus
- Rectum
- secondarily retroperitoneal viscera (loses dorsal mesentary)
- pancreas
- most of duodedenum
- ascending and descending colon
What structure separates the cloaca into a ventral urinary chamber and a dorsal digestive chamber?
urorectal septum
What is difference about the most distal part of the anal/rectal junction and the deeper portion?
What is the name of the line of fusion?
distal: from surface of body (inferior rectal arteries)
deeper: digestive tract (superior rectal arteries)
pectinate line
Where do the arteries that supply the pancreas come from?
Inferior anterior and posterior pancreaticoduodenal aa come off of the superior mesenteric artery
supeior anterior and posterior pancreaticoduodenal aa come off the gastroduodenal, off of the common hepatic, from the celiac trunk
What is the name of the process where the epithelial rod breaks down to produces a lumen?
What happens when this process fails?
recanilization
failure of recanilzation leads to stenosis
What is the cause of pyloric stenosis?
What symptom could indicate this problem?
excessive smooth muscles at the pyloric sphincter
infants prsent with projectile vomitting
What can happen if the bile duct does not canalize?
bile cannot reach the duodenum
infant is born with jaundice; fatal without surgical intervention
What is the name for abnormal migration of the ventral pancreatic duct that leaves a ring of pancreatic tissue around the duodenum?
What can happen?
Annular Pancreas
possible constriction/obstruction of the duodenum
What is the name of the following conditions?
- abnormal rotation of the midgut. Can result in a constriction or obstructin of the gut itself, or occlusion of the superior mesenteric artery
- only partial rotation occurs, caudal limb retracts first instead of cephalic limb
- PIL rotates clockwise instead of counter-clockwise. Transverse colon shofts relative to duodenum and superior mesenteric artery and may be constricted
- Volvulus
- Left-sided colon
- Reversed midgut rotation
What does not develop in Hirschsprung Disease?
The ganglion of the autonoic system do not develop, so peristaltic contractiosn do not occur
so, get congenital megacolon
