01a GI Devo Flashcards
Foregut structures
oral cavity, esophagus, stomach, proximal duodenum, thyroid, lung, liver, pancreas
Precursor of muscle, connective tissue, and other layers of gut wall (not including epithelium
Splanchnic mesoderm
Midgut structures
distal duoodenum, jeunum, ileum, caecum, appendix, ascending colon, proximal transverse colon
Hindgut structures
Distal transverse colon, descending colon, sigmoid colon
Gut wall layers
Mucosa
Submucosa
Muscularis
Adventitia
Mucosa subdivisions
Epithelium
Lamina propria
Muscularis mucosae
Submucosa contents
loose collagenous and adipose tissue, large vessels and lympphatics
INNERVATED BY MEISSNERS - submucosal PLEXUS
Muscularis externa contents
Inner circular smooth muscle
Outer longitudinal smooth muscle
Some striated muscle at proximal esophagus
INNERVATED BY AUERBACH’s- Myenteric plexus
Vagus trunk rotation
Left —> anterior
Right —> posterior
Lesser sac
space behind the stomach
Also called omental bursa
Esophageal and duodenal development
Epithelial cells proliferate to occlude lumen and then recannalize
When does development of the stomach occurr
4-7 wks
28-48 days
When does gastrulation occur?
Week 3
Primary intestinal loop
Midgut loop: divided into cranial and caudal limbs, herniates through umbilical stalk
Cranial- becomes distal duodenum through ileum
Caudal- forms caecum-transverse colon
How to tell foregut, midgut, and hindgut apart embryonically
Foregut- supplied by cephalic trunk
Midgut- Supplied by SMA
Hindgut- supplied by IMA
When does midgut elongation occur
5-10 wks (then retraction and rotationof intestine occurs)
Cloaca
expanded terminal hindgut
pinched through by urorectal spetum to create anus and ureter (attached to alantois)
Hepatic diverticulum
Forms gallbladder and liver epithelium, branch of ventral foregut that expands week 4, to from liver, GB, ad pancreas by wk 6
What causes liver bud growth and expansion
FGFs and BMPs from heart and septum transversum
pancreas formation
Dorsal foregut endoderm gives rise to head and is contiguous with bile duct- creating the main pancreatic duct (FGF2 from Notocord induction) (displaced by aorta)
Ventral foregut forms body and tail of pancreas and also gives rise to accessory pancreatic duct (devoid of sonic heddgehog signaling)
Liver parenchyma formation
Foregut epithelium
columnar—-> pseudostratified
BM degrades- BIPOTENTIAL HEPATOBLASTS differentiate from endoderm and invade mesenchyme- Hepatocytes (epithelials of liver) or Cholangiocytes (epithelials of biliary tree)
Polyhydramnios
Excess amniotic fluid- caused by duodenal atresia because intestine doesn’t absorb amniotic fluid
Hepatic biliary atesia
Can be obliteration of bile ducts
- Jaundice
- clay colored stools
Surgical duct repair or liver transplant
Gastroschisis
Abdominal viscera extruded through a lateral defect (usually right) in abdominal wall NO UMBILICAL INVOLVEMENT
*leads to serousitis 2/2 amniotic fluid exposure
