L3 - Development of the GI Tract and GI Organs II Flashcards
Feb. 6, 2019
What empties into the cloaca?
GU and GI tracts
What causes a volvulus most of the time?
Lack of fibrous tissue connecting it to adjacent structures so the gut is free to move and twist
What causes the stenotic segment in Hirschsprung disease?
absence of autonomic innervation of segment of intestine
What is the lower anal canal?
proctodeum
In a reversed rotation of the gut, where does the duodenum lie?
Anterior to the transverse colon
What are the symptoms associated with non-rotation of the gut?
Generally asymptomatic
Where does the ectoderm meet the endoderm in the GI tract?
pectinate line
Where does the cecum stand after 180 degrees of rotation?
In a subhepatic position
Where does the cecum lie in a mixed rotation/volvulus?
Inferior to the pylorus but fixed to the posterior wall by peritoneal bands
What side of the cecum does the appendix grow from?
Posterior medial side
The hindgut gets arterial supply from? It drains into? Where does lymph go?
Inferior mesenteric artery, inferior mesenteric vein, inferior mesenteric lymph nodes
What complication can occur with a subhepatic cecum?
Difficulty with diagnosing appendicitis versus cholecystitis
Patency of the omphaloenteric duct with the outer abdominal wall is called what?
Umbilical fistula
What is the difference between an omphalocele, umbilical hernia, and gastroschisis?
Omphalocele is surrounded by fetal membranes, while an umbilical hernia is covered by skin. Both herniate out through the umbilicus, but gastroschisis usually occurs lateral to the medial plane
What muscle defines low from high anorectal abnormalities?
puborectalis
What are the “twos” of Meckel’s diverticulum?
1) two feet proximal to the ileocecal junction
2) occurs in 2% of the population
3) approximately two inches long
4) contains two types of tissue: pancreatic and gastric
5) symptoms present before two years of age
6) male to female ratio is 2 to 1
Above the pectinate line, what is the blood supply? Below?
Above: superior rectal artery of the inferior mesenteric artery
Below: inferior rectal artery of the internal pudendal
Duodenal atresia and Hirschsprung disease are associated with which disorder?
Down Syndrome
What separates high anorectal abnormalities from low ones superficially?
High anorectal abnormalities have no pigmentation/dimple at anus and have a flat perineum
What is a complication of reversed rotation?
Compression of the transverse colon by the SMA
What causes anal stenosis?
Slight dorsal deviation of the urorectal septum
Above the pectinate line, what is the innervation? Below?
Above: autonomics
Below: pudendal nerve
Why might a Meckel’s diverticulum be prone to an ulcer?
Contains gastric tissue which can corrode the intestinal lining
Where is the large intestine found in non-rotation of the gut?
On the left side of the body
What causes a vitelline cyst?
Persistence of the omphaloenteric duct which continues secreting leading to cysts
What causes membranous atresia?
failure of the epithelial plug to perforate at the end of the eighth week
What are some defining characteristics of low anorectal abnormalities?
1) no anal canal
2) anal bulge
3) anal dimple or stenotic opening or abnormal opening in perineum
What is the embryological defect that causes Hirschsprung?
failure of neural crest cell migration
Which limb of the midgut grows faster?
Cranial limb grows faster than caudal limb
What axis does the midgut rotate around?
SMA
Why might a cecum be subhepatic?
Cecum may adhere to the liver not allowing it to descend into the iliac fossa
What partitions the cloaca?
urorectal septum
What is the definition of a volvulus?
Twisting of the intestines, usually the cause of an obstruction
