gut formation Flashcards
blood supply to each region of gut
foregut- celiac artery
midgut- superior mesenteric artery
hindgut- inferior mesenteric artery
how is the gut tube attached?
attached to the dorsal body wall by the dorsal mesentery
what splits the dorsal mesentery?
liver
what does the liver split the mesentery into?
lesser momentum between the stomach and liver
falciform ligament between liver and anterior abdominal wall
what is the first region to rotate?
stomach
two rotations of stomach
left to anterior
caudal to right
what do the rotations of the stomach result in?
the movement of the dorsal mesentery forming the greater and lesser omen
stomach differentiation
2nd month
appearance of rug and gastric pits
differentiation requires EMT
Problem with stomach development
pyloric stenosis
pyloric stenosis explained
failure to form muscular structure at pyloris
lack of SOX9
abnormality of pyloric sphincter, resulting in projective vomiting
important signals in formation of liver
FGF signals from adjacenct cardiac region induce liver field
what structure does the liver originate from?
the gut tube
midpoint of the descending duodenum
stages of liver development
- hepatic diverticulum moves into the ventral mesentery
- branch into hepatic cords
- hepatic cords communicate with septum transverse mesoderm to branch into hepatic bud that forms the liver and cystic bud that forms the gall bladder
- liver suddenly begins to grow very rapidly in 10th week
- bile production develops in 12th week
gut diverticula definition
outpouching of gut tube
why is the development of the pancreas unusual?
develops from two distinct buds
from which part does the pancreas arise of the gut tube?
mid part of the duodenum
explain two buds
dorsal bud- body and tail
smaller ventral bud- uncinate process and head
what induces the buds to form?
fgf10 from notochord for dorsal bud
Vegf for ventral;
where do the exocrine and endocrine cells develop from?
dorsal bud
how do pancreatic buds develop?
branching morphogenesis
- free ventral pancreatic bud rotates around the axis of the duodenum and joins the dorsal bud
abnormalities of pancreatic rotation
annular pancreas
pancreatic tissue surrounds the duodenum and constricts it
what occurs due to expansion of liver?
stomach pushed to the right
pancreas pushed posteriorly causing it to join with the dorsal body wall, becoming secondarily retroperitoneal
what forms the axis for the midgut rotation?
superior mesenteric artery and vitelline duct
what causes asymmetry of gut?
asymmetric expression of BMP2 in gut and mesentery drives expression and rotation
stages of midgut rotation
- proliferation in midgut causing increased growth
- the gut tube rotates 90 degrees around the axis of the vitelline gut
- growth becomes excessive, exceeding the capacity of the coelomic cavity
- undergoes physiological herniation where it moves out into the umbilical cord
- gut returns to abdominal cavity, cecum moves down
- further 180 degree anti clockwise rotation, leading to a total of 270 degrees anticlockwise
hindgut derivatives
1/3 distal transverse colon
descending colon
rectum
superior part of anal canal
what happens during rotation?
ascending and descending colon pushed against posterior wall leading to formation of retroperitoneal structures
what do the gut tube and urogenital tube open into?
the cloaca
what happens to the cloaca after?
urorectal septum grows down between the two of them to partition them
separating the urogenital system from rectal
form separate anus and urethra
what is the enteric nervous system formed of?
neural crest cells
migrate along the gut tube
problem with neural crest cells
hirschprung’s disease
failure of neural crest cell migration
absence of enteric nervous system
how does the spleen develop?
separate to the gut
entirely mesodermal
hiatus hernia definition
problem with the septum transversum, weaker diaphragm, causes stomach to be lodged in mediastinum
