embryo devel GI second set of q Flashcards
rotation of foregut
stomach moves to the left, liver moves to the right
relative size of the two peritoneal cavities changes
right side gets smaller!
what part of the doudenum is considered midgut?
duodenum distal to major papilla
gut atresias and stensoses: upper duodenum and caudad to the duodenum
upper part usually result of failure to recanalize
distal to duodenum, probably a vascular compromise
apple peel atresia
proximal jejunum, intestine is short, and the portion distal to the defect is coiled around the mesenteric remnant
a patient comes in with a problem the proximal jejunum and, and low body weight
apple peel atresia
@ 6 weeks, the developing fetus shows signs of herniation
this is natural because the midgut is growing rapidly and pushes into the umbilical cord. simultaneously, the gut loop rotates ~90 degrees COUNTERclockwise around the superior mesenteric a.
physiological herniation of midgut
is perfectly normal, midgut is growing into umbilical cord while the loop is rotating counterclock wise, 90 degrees
Primary intestinal loop: two parts, the cranial end and the caudal end
cranial end becomes the distal duodenum to ileum
caudad end becomes the lower ileum to proximal 2/3 transverse colon
rotations of the midgut
at 6 weeks the midgut expands into the umbilical cord and rotates 90 degrees counterclockwise
at 10 weeks, the herniated loop returns to the abdominal activity and rotates an additional 180 degrees (270 degrees total)
Malrotation of the midgut
partial rotation only, increases “entrapment” of portions of the intestine.
child presents with bilious vomiting within the first week after birth, diarrhea, septic shock, abnormal distention and food intolerance. diagnosis
malrotation
Volvulus
volvulus is the abnormal twisting of the intestine which causes an obstruction……compromises intestine or blood flow
usually an axial rotation around a certain part of the intestine and its mesentery
Bilious Emesis
may indicate malrotation and volvulus
Intussusception
enfolding one segment of intestine within another
a patient complains of abdominal pains that become worse and worse, recurring attacking of cramping, and “jelly stools”
intussusception
indicates enfolding of one segment of the intestine within another
Ladd’s bands
fibrous stalks of peritoneal tissue that attach to cecum to the abdominal wall and create an obstruction of the duodenum. this condition is found in malrotation of the intestine.
Body wall defects
omphoceles, gastroschisis, prune belly syndrome
omphaloceles
herniation of abdominal content through enlarged umbilical ring
NORMAL IF temporary
gut should return into abdomen as the embryo grows
omphaloceles: cause
midgut fails to return to abdominal cavity
pale, shiny sac protrudes from base of umbilical core
Gastroschisis
failure of the anterior abdominal wall musculature to close during folding. the gut is not surrounded by a membrane
survival rate excellent
this is distinguished from the omphalocele because it is not occuring through the umbilical cord
prune belly
Eagle-Barrett syndrome
triad: anterior abdominal wall musculature is deficient or absent
urinary tract anomalies
bilateral cryptorchidism
occurs almost exclusively in males
BLADDER, ABDOMINAL WALL, KIDNEY, UNDESCENDED TESTES
PBS Etiology: 2 hypothesis
Urinary tract obstruction as the result of a prostate hyoplastic or dysplastic tract obstruction, leadings to overdistension of the bladder and the upper urinary tract. streched abdominal wall. causes damage to abdominal musculature
primary medosermal development defect. insult between 6-10 wks, disrupts intermediate lateral plate mesoderm which gives rise to both abdominal musculature and the prostate
Ileal diverticulum
meckel’s diverticulum
remnant of vitelline duct
asymptomatic
gastric/pancreatic tissue inside
failure of the vitelline duct to close
rule of 2’s
2% prevalence
2:1 female predominance
2 feet from ileocecal valve in adults, location
half of patients who are symptomatic are younger than 2 years of age
symptoms of the ileal diverticulum if fistula is present
fistula present
decal discharge through umbilicus
a guy is shitting through his umbilicus
ileal diverticulum with fistula present
Hirschsprung’s disease
congenital aganglionic megacolon
a motor disorder of the colon causing functional intestinal obstruction
failure of neural crest cells to migrate and establish colonic ganglions
no parasympathetic innervation. no peristalsis, or no relaxation, results in a functional obstruction
if hirschsprung’s is identified, where would it be most lethal? what is the treatment
in the proximal parts of the intestine/colon
surgery: aganglionic part removed, ganglionic part connected to colon/rectum
what does “rotation” of the gut do generally? name four things
1) reduces space
2) changes organ relationships
3) causes changes of some of the dorsal mesenteries
4) structures will be primarily or secondarily retroperitoneal
left peritoneal diverticulum —>
greater sac
right peritoneal diverticulum –>
lesser sac
partitioning of the cloaca
develops from the hindgut of the endoderm
cloaca divided by urorectal septum into urogenital sinus and rectum
defects in cloaca partitioning
failure of folds to develop
rectourethral fistula
defects in cloaca partitioning
failure of folds to develop in men
rectoprostatic fistula
defects in cloaca partitioning
failure of folds to develop in women (2)
rectocloacal canal
rectovaginal fistula
what three defects can occur during cloacal partitioning?
rectovaginal fistula
rectoprostatic fistula
rectocloacal canal
malalignment of folds
rectourethral fistula involving rathke fold
tourneux fold
anorectal malformations
occurs when the rectum ends in a blind pouch and does not connect with the external environment
stenosis, or narrowing of the anus, or absence of the anus may be present
Anorectal malformations
spectrum of defects with “high” and “low” species
anal membrane fails to perforate
anal canal ends as blind sac below pelvic diaphragm (anal agenesis)
rectum ends as blind pouch above the pelvic diaphragm (anorectal agenesis, most common)
anal canal ends as a blind pouch BELOW pelvic diaphragm
anal agenesis
anal canal ends as blind pouch ABOVE pelvic diaphragm
anorectal agenesis, most common
imperforate anus symptoms and signs
absence of misplacement of anus anus opens near vagina anus opens into the vagina, penis, scrotum, urethra no passage of stool in 24-48 hrs abdominal distention
high anorectal malformations
these are the ones with the “bad” prognosis, since there are no pelvic muscles that can compensate for passing stool
high rectovaginal fistula
rectobladderneck fistula
low anorectal malformations
these are the “good” ones because other muscles can be trained to help pass stool
vestibular fistula
rectourethral bulbar fistula
Clinical prognosis: imperforate anus
a colostomy is indicated after birth, with surgical correction prognosis is excellent
Rectourethral fistula
colostomy before repair period. long term prog. for normal urethral and rectal function is good
rectovesical fistula
usually also have poorly developed sacral bones and sphincters. prognosis for normal bowel function is poor.
