what is in the midgut
distal duodenum jejunum ileum cecum ascending colon first half of transverse colon
what is in the foregut
Resp tree esophagus stomach proximal duodenum pancreas + ducts liver + gall bladder
what is in the hidngut
last part of transverse colon descending colon sigmoid colon proximal 2/3 rectum
what is dorsal mesentery made of? function? what does it give rise to?
• Dorsal mesentery connects gut tube with posterior abdominal wall • Mesentery carries blood vessels from the aorta to the gut tube • Continuous from cranial to caudal end gives rise to Greater omentum - 4 layered pocket hanging below stomach, superficial to ab organs
what is ventral mesentery made of? gives rise to?
ventral mesentery connects gut tube to the anterior body wall liver liver develops in ventral mesentery and grows into 2 parts: 1) anterior -Falciform ligament 2) posterior - Lesser Omentum with the Hepatoduodenal LIgament and Heptogastric Ligament ventral mesentery ONLY IN FOREGUT
Dorsal segmental arteries
supplies somites/muscle mass gives rise to posterior intercostals
Lateral segmental arteries
supply developing kidneys gives rise to renal arteries
Ventral segmental arteries
supply gut tube, through dorsal mesentery. initially paired, some drop out or fuse. 3 unpaired ventral arteries remain: celiac artery (foregut) SMA (midgut) IMA (hindgut)
describe the development of intestines
around 4-5 weeks the intestines are growing rapidly - gut tube grows faster than peritoneum so the intestines bulge out ventrally into umbilicar cord around weeks 8-9, there is enough room so intesttines come back in as intestines re-enter peritoneal cavity, they rotate 270 degrees counterclockwise around the Vitelline Duct/SMA. brings structures into their position - LI is anterior/framing the SI. cecum will but up near liver but will grow down. cecum elongates without growing wider - forms vermiform appendix
describe types of clinical issues due to Malrotation of Gut
1) Non rotation - 2) Reversed Rotation - Situs Inversus. OK if everything flips. 3) Subhepatic cecum - cecum does not grow down and remains at liver
gut tube does not retrat, remains in the umbilical cord and covered in amnion
like omphalocele (gut tube does not retract out of the umbilical cord like it sholud) however, guts are NOT covered in amnion
vitelline duct normally closes/dissolves after guts retract. Vitelline duct remains and you get outpocketing of the SI
vitelline duct remains and forms a fibrous cord. guts anchored to anterior wall and cant move
vitelline duct remains and forms a cord with a lumen - chyme can leak out!
vitelline duct remains and twists
type of issues due to malrotation of the intestines cecum does not grow down like it should, remains up near liver
what is urorectal septum
in development the urogenital and digestive systems have a common outflow tract called Cloaca - we need to separate Urorectal Septum - tissue between allantois and hindut that grows down and forms the Anorectal canal and urogenital sinus
how does liver form? what signals?
High BMP and FGF will tell endoderm to be liver BMP from septum transversum FGF from cardiogenic plate
what signals forms pancreas? ventral and dorsal?
Low BMP and FGF - default tissue is ventral pancreas Dorsal pancreas develops on the other side of gut tube in presence of Shh
what signals form exocrine vs. endocrine pancreas? cells within endocrine?
Exocrine pancreas - Notch sensitive Endocrine pancreas - Notch insensitive Pax 6 - Alpha (glucagon) and Gamma (PP) cells Pax 4 - beta (insulin) and delta (SS) cells - Develop LATER
what is Annular Pancreas
Ventral pancreatic bud does not move properly - can surround/narrow the duodenum
Coelom ? Development of
Intraembryonic coelom will give rise to thoracic and abdominal cavities Coelom = space lined by epithelium but derived from mesenchyme In the lateral plate mesoderm, a space develops between the somatic and splanchinc mesoderm layers. EEC = Extraembryonic Coelom = Chorion Cavity Over time IEC and EEC fuse - only in areas where there are somites. Lateral folding will form defined IEC and close it Cephalocaudal folding will get rid of EEC.
what are the 4 parts of the diaphram?
1. septum transversum 2. Pleuroperitoneal membrane (used to be capsules of mesonphric kidneys) 3. mesentery of esophagus 4. posterior body wall SPEP
how does diaphragm develop? (thorax and abomden separation - peritoneal cavity)
as septum transversusm moves down, it hits different strucutres. stops at posterior body wall. Diphragm forms from things septum transversum hits
how does pleural cavity and pericardial sac develop/separate?
intussuseption of common cardinal veins - forms a Pleuropericardial membrane