L4 dev of GIT

Question 1

LO2: how coelomic and perit cavs dev.

Answer 1

• intraemb coelom- primord all bod cavs. mesod mid lay- somat mesod outs, splanch inside. mesod lat sp opens as emb folds, leafs meet up=sp, cyling shape.
  coelom bgins 1 lay cav, endod lined tube. later subdiv by fut diaph into abdo and thoracic cav.
  -perit and perit cav: perit mem lines coelom, invests viscera. poten sp. gut tube elongs and rolls, perit also changes.

Question 2

LO3: fate emb dorsal and ventral mesents.

Answer 2

-mesent=doub lay perit susp gut tube from abdo wall. blood and nerve supp and mobil. splanch mesod susp primit gut in coelom, condensat this mesod- mesent. dorsal mesent susps ent gut tube from dorsal wall. went only in reg of foreg- free edge.

Question 3

LO4: how greater and lesser omenta and mesent of small int dev. relate to arr in ad and neonate.

Answer 3

-dorsal and vent mesent div cav to L and R sacs in foreg only. L greater sac, R lesser beh stom as lose vent att.
omenta= spec regs perit. greater from dorsal mesent. lesser vent, free edge portal triad.
-greater and lesser sacs and omenta formed by rotat stom.
round longit axis and anteropost. init this puts greater curvat R, lesser L then cardia and pyloris move horiz and push greater curv infer. stom rotat puts vagus nerves ant and post. shidt cardia and pyloris from midline=oblique. moves lesser sac beh stom and forms greater omentum.
-liv dev in leaves of vent mesent.
-perit reflec- change in direc from pariet to visc perit. from mesent to visc perit. etc.

Question 4

LO5: why some abdo organs retroperit. eg asc and desc colon and duod.

Answer 4

-retroprit no susp in abo cav, never had mesent. secondaril retrop had mesent but fused at post abdo wall.
-foreg derivs- foreg=lung bud to liver bud.
wk4 resp divertic forms in vent wall foreg at junc with pharyng gut. resp primordium (vent). oesoph (dorsal).
trancheosoph septum forms x divertic, abnorm posit 1/3000 live birtheg proxim blind end, tracheosoph fistula, oesoph atresia.
-stom- faster growth dorsal border. rotat changes posit of dorsal and vent mesents- omental bursa formed, lesser displ post from R.
-foreg der gls- vent mesent= liv, biliary sys, ucinate proc, head panc.
dorsal =sup head, neck, bod, tail panc.
-liver- from hepat bud in vent mesent btw 2 leafs. perit reflecs- wk6 bare are top, lesser oment, falcif lig to ant wall, splits as liver grew ins 2 mesent. ant att is deriv of vent mesent. bare area atts diaph.
-duod- caudal foreg and cranial midg. gorw rap=c loop when stom rotates ant post. wk 5 and 6 lumen destr and re canal. stom rotat pushes R and post.

Question 5

LO6: desc dev musc and fascial lays abdo wall incl inguinal canal.

Answer 5

-sec retroperit- mesent lost fus post wall pariet perit due to GIT expans= fusion fascia.
eg stom grow pushed ag post wall, apriet perit paper over it=fascia.
sec retroperit foreg=duod excep cap, panc.

Question 6

LO7: expl dev basis umb and inguinal hernia.

Answer 6

-?

Question 7

LO1: expl how fold in wk4/5= primit gut, abdo wall and coelomic cav.

Answer 7

-emb folds lat= vent bod wall, primit gut becomes tubul.
craniocaudally= cranial and caudal pocks form YS endod begins primit gut dev. blind pockets, opening at midgut.
foregut cranial and hindgut caudal blind divertic. midgut openin ginit and is contin with YS.
-primit gut tube dev wk 3. pinches off YS, endod lining from stomatodeum fut mouth to proctodeum fut anus. opening at umbilicus. ext lining der from splanchnic mesod fut musc and visc perit. susp in intraemb coelom by doub splanch mesod.
-ad derivs:
foregut- oesoph, stom, panc, liv, gallb, duob proxim to papill duct.
midg- dustal duod, jej, ileum, cecum, asc colon, proxim 2/3 transv.
hindg- distal transv, desc colon, sigm, rectum, upp anal canal, int lining bladd and urethra.
- blood- foreg coeliac trunk, midg SMA, hindg IMA.
close to junc mixed supp-
proxim duod gastroduod art and sup pancreaticoduodenal (CT), distal infer pancreaticoduod (SMA).
panc head sup pancduod (CT), and infer (SMA).