anatomy and physiology

superior mesenteric artery

• Right: ileocolic, right colic, and middle colic arteries.
• left: 12-20 jejunal and ileal branches on left
• behing superior border of pancreas at L1
• cecum to most of transverse colon, entire SI, pancreas, and occasionally liver
• crosses 3rd ptn of duodenum

• superior ascending, anterior cecal, posterior cecal, appendicular, ileal
• most constant

• also can arise from ileocolic or middle colic
• ascending colon and hepatic flexure

• highest, close to inferior border of pancreas
• right branch > right transverse and hepatic flexure
• left branch > distal transverse

• RC: arises from ileocolic mor MC
• absent 2-18%

• MC:absent 4-20%
• accessory 10%

the inferior mesenteric artery

• 2 cm above CIA bifurcation
• L2-L3
• left colic and 2-6 sigmoidal arteries
• becomes SHA (SRA)

ascending branch:arcade of riolan

Descending branch: desc colon

• (1) a simple columnar epithelium which forms crypts,
• (2) lamina propria,
• (3) muscularis mucosa,
• (4) submucosa,
• (5) muscularis propria formed by an inner circular and outer longitudinal layer of smooth muscle,
• (6) serosa.

• (1) absorption of water, SCFA, baterialmetabolitesand electrolytes
• (2) propulsion and storage of unabsorbed fecal waste for evacuation

• preganglionic vagal fibers and pelvic fibers
• colonic motility

• superior mesenteric plexus, inferior mesenteric plexus, and the hypogastric plexus
• inhibits colonic motility.

• (myenteric or Auerbach’s/submucous
• or Meissner’s).
• An absence of intrinsic plexuses occurs in Hirschsprung’s Disease resulting in tonic wall contraction and functional obstruction.

• irritable bowel syndrome,
• slow-transit constipation,
• colonic pseudo-obstruction,
• post-operative ileus

• individual phasic contractions of short and long duration
• oraganized groups of contractions
• special propulsive contractions

• basic unit
• short <15 sec
• long 40-60 sec
• highly disorganized in time and space
• mixing, kneading, slow distal propulsion

Giant migrating contractions

• involuntary-short, long duration, GMC>propulsion
• voluntary

• bowel wall m. relaxes > distention > accomodation
• sensory receptors in anal canal > threshold stimulation of afferent n endings > involuntary anal reflex
• mass peristaltic wave abouve mass, distal rectum and IAS relax, EAS contracts all at same time >accomodation or , if elimination to proceed > voluntary inhibition of EAS contraction

glottis closes > Intraabdominal pressure inc, voluntary m of abdominal wall contracted, diaphragm descends > relaxation of pelvic m > descent of pelvic floor, straightening of anorectal angle

• rests on iliacus and psoas major
• anomaly of fixation > volvulus

• rest on psoas muscle in inferomedial course
• crossed by spermatic vessels anteriorly
• crossed by genitofemoral nerve posteriorly

• lateral to IVC
• crossed anteriorly by spermatic vessels, R coloc and Iliocolic AA
• crosses in front of CIA bifurcation in pelvis
• vas def crosses lateromedially on its superior aspect
• female: crosses posterior layer of broad ligament
• uterine artery crosses above and lateromedially

dissect greater omentum off anterosuperor aspect to mobilize and to enter lesser sac of peritoneum

• s3
• sacral promonotory

end is anorectal ring

• perirectal areolar tissue
• thicker posteriory
• contains terminal branches of IMA
• enclosed by fascia propria

• distal condensation forms lateral ligaments
• minor branches of MRA

presacral hemorrhage

fascia of waldeyer

• extramesorectal-removes denovilliers f
• risk of injury to periprostatic plexus (S and PS injury)

bowel wall, apendices epiploicae, nodules of gerota

marginal artery and arcades, most numerorsu

primary colic AA

• IMA, SMA
• >paraaortic chain>cisterna chyli

IM nodes>paraaortic nodes

sup hem A>IMA

middle hem A > internal illiac

IM > internal illiac

• inf rectal lymphatics> sup inguinal nodes
• inf hem A

post vaginal wall, uterus, cervix, broad ligament, fallopian tubes, ovaries cul de sac

broad ligament, cul de sac

no spread

lower six thoracic > celiac, preaortic, SM ganglia > postganglionic fibers along SMA > r. colon

R post vagus, celiac plexus > along SMA > r. colon

pre ganglion L1-L3 > preaortic plexus >post ganglionic along IMA and Sup rectal > left colon and upper rectum

S2-S4 (nervi erigentes) > pelvic plexus (join symp hypogastric nn) > inf. mesenteric plexus > left colon, upper rectum

aortic plexus, lumbar splanchnic n > presacral nn > hypogastric plexus > hypogastric nn > pelvic plexus (next to lateral stalks)

S2-S4 (nervi erigentes) > pelvic plexus (join symp hypogastric nn) > lower rectum, upper anal canal.

• subdivision of pelvic plexus
• on denovilliers f.

ejaculation, inhibition of vasoconstriction

arteriolar vasodilation

high ligation of IMA>symp preaortic nn

level of sacral promontory or in the presacral region > sup hypogastric plexus, hypogastric nn.> retrograde ejaculation (intact n. erignetes) and bladder dysfunction

pelvic plexus injury (traction on rectum or division of lateral stalks)

periprostatic plexus > erectile impotence, flaccid, neurogenic bladder.

L5

s2-4

• pelvic surface, s2-s4
• inf surface> perineal branch of pudendal n

PR: also gets from inf rectal nn

s2,s3>inf rectal branch of pudendal n

perineal branch of S4

• meissners : touch
• Krause's bulb: cold
• Golgi-mazzoni bodies: pressure
• genital corpuscles: friction

inf rectal branch of pudendal n