L8 dev of mid and hindgut

Question 1

LO2: disc dev basis comm congenit defects GIT incl atresia and stenosis.

Answer 1

-maj complics of midg defecs- volvulus= strang. twst int loops, too mob=duod obstruc and dilat. ichaemia- SMA compress transv colon.
cecal bud not desc= no asc colon, sub hepatic cecum. vovlulus of large int, wrap duod=obstruc.
-YS remn- vitelline duct persis, should lose patency once hernia resolved and become cord.
vitelline cyst- mid fluid filled, fib str connec bowel and abdo wall formed from duct.
vitell fistula- direc connec umbilicus and int duct.
meckels divertic- comm. divertic rems. us not fib cord att to wall. rule of 2’s- 2% pop, 2 feet from ileocecal valve, 2 inch long, us detec under 2yr, 2:1 male to fem. can cont ectopic gastric or panc tiss in ileum, proteolytic enz=inflamm. midg ori so can present like appendicitis.
-recanalisat- primit gut simp tube. rap cell growth part/compl oblit lumen. oesoph, bile duct, small int. wholly/part unsucc recanal=atresia/stenosis
-atresia= lumen oblit. stenosis= lumen narr. most likely in duod. likely cause incompl cabalisat. vasc accid also contrib. BUT..
pyloric stenosis- hypertroph of circ musc pyloric sphinct, NOT recanal fail. comm in infant, narr exit= projec vom.
-atresia and stenosis: incid- duod then jej and ileum then colon. upp duod us canal fail. lower us vasc acid due to malrotat, volvulus, bod wall defec.
-defec ant abdo wall:
umb and inguinal hernia.
gastroschisis- gut tube and derivs outs. fail close abdo wall div fold. regress of L umb vein. lin defect. caught wk 20. isol, good prog if loop healthly.
omphalocoele- persis physiol herniat in umb cord. cov by amnion. can assoc other struc defec.

Question 2

LO3: desc partit of cloaca and dev anal canal.

Answer 2

-hingut= distal 1/3 transv. desc colon. rectum. super anal canal. epith urin bladd.
-anal canal div by pectinate line- diff art supp, V+L drain, and innerv.
-cloaca- end of hindg at 6 wk. blind divertic. exit for GI, repro, urin tract. cloacal mem seps outs. anteropost subdiv.
-parit cloaca- mesod grows down inot= div urogenit sinus (bladd) and anorectal canal post. end wk 7=urorectal septum. proclodeum (anal pit) as mesod grows. septum meet wall= perineal bod. then CM rupt=urethra and anus sep. because was in pit, some mesod lines anus.
-above pectinate- IMA supp. S2,3,4 pelvic PS (hindg). col epith. lymph drain= int ileac nodes.
below- pudendal A der from bit with ectod lining. S2,3,4 pudendal N, somatic. drain= superfic inguinal nodes.
contrib 2 emb tiss= above only feel stretch, below sensit to temp, touch and pain.
-visc pain- poor loc as innerv by splanchnic nerves. patt refl emb ori. irrit visc perit only, sense distens.
foregut and derivs- epigastrum.
midgut- periumb.
hindgut- suprapubic.
pariet perit somatic innervat can loc.
-hindg abnorm- imperforate anus- fail rupt anal mem. anal/anorectal agenesis. hindg fistulae- connec bladd and rectum.

Question 3

mid vs hindgut.

Answer 3

-fate mid and hindg mesents-
mesents retained by- jej, ileum, appen, transv, sigm.
fixed mesents- duod, asc colon, desc, rectum (no perit distal 1/3). adhere post perit=fixed.
-fate dorsal and vent mesent-
dorsal= greater oment, gastrolienal lig stom atts to spleen, lienorenal lig, mesocolon, mesent proper jej and ileal loops.
vent= lesser oment foreg to liver. falcif lig liv to vent wall.
-mid vs hindg-
midg- SMA+V, innerv PNS vagus, SNS super mesent gang and plexus.
hindg- IMA+V, PNS pelvic S2,3,4. SNS IM gang and plexus. duod ori of anal canal.
-see notes.

Question 4

LO1: desc role of rotat of midgut loop in estab dispos of abdo viscera. mid and hindgut derivs-expl dispos lower GIT, to have mesent or not.

Answer 4

primit gut tube init same length intra emb coelom. exts more than sp has so loops and herniates. rotates and twists.
-midgut gives rise to- small int incl duod after bile duct. cecum and append. asc colon. proxim 2/3 transv.
-prim int loop- midgut sec of tube lot elong. while liv growing. makes loop that- has SMA as axis, supps midgut, is connec to YS by vitelline duct, has cranial and caudal limbs.
-physiol herniation. norm. wk6. int into umb cord. vitell duct loop pushes outs bod. cov by amnion.
-midgut rotat in umb cord- 3x90 deg.
180 deg dur herniat. 90 deg on return to abdo cav. cranial return abdo cav first-moving L.
first 90 deg- cranial elong more= v convol in umb cord.
3rd- cranial derivs back into cav and pushed L. final cecal bud drop down=asc colon. caudal now ant to cranial limb?
-cranial derivs- dist duod, jej, proxim ileum.
caudal- dist ileum, cecum, appen, asc colon, proxim 2/3 transv.
-incompl rotat- loop only 1 90 deg rotat=L sided colon. limbs no x and cranial not L.
rev rotat- loop 1 90 deg clockw= transv colon post to duod.
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