Digestive Development (Embryo) Flashcards
How is the gut formed?
Foregut, midgut and hindgut from portion of the yolk sac
Endodermal epithelium
Splanchnic mesoderm for CT and muscle
What is the only part of the digestive system not formed from endoderm?
Anal canal which is ectodermal
What structures are in the foregut?
Esophagus, stomach, descending duodenum (liver, pancreas)
Innervated by celiac artery
What structures are in the midgut?
Ascending duodenum, jejunum, cecum, colon, ascending part of the transverse colon
Innervated by cranial mesenteric artery
What structures are in the hindgut?
Part of the transverse colon, cloaca (rectum)
Innervated by caudal mesenteric artery
Development of the esophagus
Major growth is longitudinal growth in neck and thorax
Failure to grow = mal-positioning of the stomach
Development of the stomach
Dorsal enlargement undergoes 90 degree rotation that brings the dorsal part of the stomach to the left and ventral part close to liver
@ birth the _________ is 3-4 times bigger than the rumen?
Abomasum (enzymes needed for milk from mother)
Physiological atresia
Early embryo entire gut is occluded
Temporary and re-canalization begins by the end of the embryonic stage
Physiological herniation of the gut
Early embryo, midgut grows faster in length and can’t be accommodated in abdominal cavity –> herniates into extraembryonic coelom of the umbilical cord –> herniated loop undergoes 360 degree rotation
What is the axis of the herniated loop?
Cranial mesenteric artery
Ascending colon on the pig and ox
Coiled in ox
Spiral in pig
Ascending colon of the horse
Folds upon itself to form pelvic, sternal and diaphragmatic flexures
Development of the rectum
Partitioning of the cloaca by urorectal septum that separates the rectum from the urogenital sinus
Cloaca
Common opening for the digestive, urinary and genital systems
Development of the anal canal
In-growth of the skin ectoderm (proctoderm) that meets with the rectal endoderm forming the cloacal membrane –> cloacal membrane ruptures and rectum and anal canal continuous
What forms the anal sacs in carnivores?
2 lateral outpouchings of the ectoderm and associated glands
Abnormalities of anal canal development
Anal canal atresia, rectal atresia (failure to canalize)
imperforate anus
Development of sinusoids (liver)
Umbilical and vitelline veins passing through liver
Development of hepatic cords (liver)
Ventral hepatic diverticulum (endodermal)
Hepatic diverticulum branches, terminal branches become bile canaliculi (drain bile from hepatocytes to bile duct)
Development of the pancreas
Develops as dorsal and ventral endodermal primordia of the duodenum
Dorsal primordia
Grows into greater omentum
Bulk of left pancreatic lobe derived
Ventral primordia
Forms most of the right pancreatic lobe
Openings int he pancreatic duct system
Pancreatic duct (opens in conjunction with bile duct)
Accessory pancreatic duct (opens caudal to bile duct)
Achalasia
Continual constriction of esophageal musculature
Usually do to neuromuscular defect
Common in carnivores
Symptoms: vomiting after eating solid food
Mal-positioning of the stomach
Failure to descend, rotate or rotate on the right side instead of the left
Atresia of intestine
Closure of digestive tube usually due to a failure of the gut to recanalize
Umbilical Hernia
Results from incomplete closure of the umbilical ring
Persistent Meckel’s diverticulum
Ileal fistula/ vitelline fistula or cyst of sinus
Failure of yolk sac remnant to atrophy
