Download embryo ch 15 [10-26

embryo ch 15



















Pharyngeal gut – from the oropharyngeal membrane to the respiratory diverticulum
Foregut – from the pharyngeal tube to the liver outgrowth
Midgut – from the liver bud to the junction of the right 2/3 and left 1/3 of the transverse colon
Hindgut – from the left third of the transverse colon to the cloacal membrane
Epithelial lining of tract and parenchyma of glands – endoderm
Stroma (connective tissue) from glands, muscle, connective tissue, and peritoneal components
of wall – visceral mesoderm
Congenital hiatal hernia – when the esophagus fails to lengthen sufficiently and the stomach is
pulled up into the esophageal hiatus through the diaphragm
Omental bursa – lesser peritoneal sac – space behind the stomach
Lienorenal ligament – connects the spleen to the body wall near the left kidney
Gastrolienal ligament – connects the spleen to the stomach
Pyloric stenosis – when circular and (to a lesser degree) longitudinal muscles of the pylorus
hypertrophies
o Treatment with erythromycin in newborn period substantially increases risk for pyloric
stenosis
o Characterized by extreme narrowing of pyloric lumen and passage of food is obstructed,
resulting in severe projectile vomiting
Duodenal cap by the pylorus of the stomach is the only part of the duodenum that remains
intraperitoneal (rest is retroperitoneal)
Septum transversum – mesodermal plate between pericardial cavity and stalk of yolk sac – liver
bud rapidly proliferates and penetrates this plate
When liver cells have invaded entire septum transversum, so that it bulges caudally into the
abdominal cavity, mesoderm of septum transversum lying between liver and foregut and liver
and ventral abdominal wall becomes membranous, forming lesser omentum and falciform
ligament, respectively
o Together called ventral mesentery
Bare area of the liver – where surface of liver is in contact with future diaphragm and is never
covered by peritoneum
Extrahepatic biliary atresia – bile ducts fail to recanalize and remain solid cords they started as
o 15-20% of patients with this have proximal ducts and a correctable defect but the rest
will die without a liver transplant
Retrocolic hernia – entrapment of portions of small intestine behind mesocolon
Meckel’s diverticulum (ileal diverticulum) – outpocketing of the ilem that forms if a small
portion of the vitelline duct persists
o Does not usually cause any symptoms, but if it contains heterotropic pancreatic tissue or
gastric mucosa, it may cause ulceration, bleeding or even perforation
Sometimes both ends of vitelline duct transform into fibrous cords and middle portion forms
large cyst (enterocystoma or vitelline cyst)
o




Intestinal loops may twist around fibrous strands and become obstructed causing
volvulus
If vitelline duct remains patent over entire length, forming direct communication between
umbilicus and intestinal tract, it is an umbilical fistula (vitelline fistula) and fecal discharge may
be found at umbilicus
Apple peel atresia – 10% of all atresias – atresia in proximal jejunum, and intestine is short, with
portion distal to lesion coiled around mesenteric remnant
Rectourethral or rectovaginal fistulas – rectum connects with vagina or urethra instead of anus
(on top of imperforate anus malformation)
Congenital megacolon – due to absence of parasympathetic ganglia in bowel wall (aganglionic
megacolon or Hirschsprung disease) – can cause mutations in RET gene