anatomy and physiology

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anatomy and physiology
2011-07-11 10:40:19

arteries, nerves, ureter, fascia
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  1. Arterial blood supply cecum to splenic flexure
    superior mesenteric artery
  2. SMA
    • 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
  3. Ileocolic
    • superior ascending, anterior cecal, posterior cecal, appendicular, ileal
    • most constant
  4. Right colic
    • also can arise from ileocolic or middle colic
    • ascending colon and hepatic flexure
  5. Middle colic
    • highest, close to inferior border of pancreas
    • right branch > right transverse and hepatic flexure
    • left branch > distal transverse
  6. IC, RC, MC variations
    • RC: arises from ileocolic mor MC
    • absent 2-18%

    • MC:absent 4-20%
    • accessory 10%
  7. left and sigmoid colon is supplied by
    the inferior mesenteric artery
  8. IMA
    • 2 cm above CIA bifurcation
    • L2-L3
    • left colic and 2-6 sigmoidal arteries
    • becomes SHA (SRA)
  9. Left colic
    ascending branch:arcade of riolan

    Descending branch: desc colon
  10. colon wall histology
    • (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.
  11. The function of the colon is
    • (1) absorption of water, SCFA, baterialmetabolitesand electrolytes
    • (2) propulsion and storage of unabsorbed fecal waste for evacuation
  12. PS colon
    • preganglionic vagal fibers and pelvic fibers
    • colonic motility
  13. symp colon innervation
    • superior mesenteric plexus, inferior mesenteric plexus, and the hypogastric plexus
    • inhibits colonic motility.
  14. intrinsic plexus colon
    • (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.
  15. Disorders of colonic motility
    • irritable bowel syndrome,
    • slow-transit constipation,
    • colonic pseudo-obstruction,
    • post-operative ileus
  16. 3 types of contraction
    • individual phasic contractions of short and long duration
    • oraganized groups of contractions
    • special propulsive contractions
  17. individual phasic contractions of short and long duration
    • basic unit
    • short <15 sec
    • long 40-60 sec
    • highly disorganized in time and space
    • mixing, kneading, slow distal propulsion
  18. special propulsive contractions
    Giant migrating contractions
  19. defecation: 2 stages
    • involuntary-short, long duration, GMC>propulsion
    • voluntary
  20. defecation
    • 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
  21. defecation
    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
  22. Cecum
    • rests on iliacus and psoas major
    • anomaly of fixation > volvulus
  23. Ureters
    • rest on psoas muscle in inferomedial course
    • crossed by spermatic vessels anteriorly
    • crossed by genitofemoral nerve posteriorly
  24. R ureter
    • 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
  25. Transverse colon
    dissect greater omentum off anterosuperor aspect to mobilize and to enter lesser sac of peritoneum
  26. rectosigmoid junction
    • s3
    • sacral promonotory
  27. rectum
    end is anorectal ring
  28. mesorectum
    • perirectal areolar tissue
    • thicker posteriory
    • contains terminal branches of IMA
    • enclosed by fascia propria
  29. fascia propria of rectum
    • distal condensation forms lateral ligaments
    • minor branches of MRA
  30. presacral F
    presacral hemorrhage
  31. retrosacral fascia
    fascia of waldeyer
  32. denovilliers f
    • extramesorectal-removes denovilliers f
    • risk of injury to periprostatic plexus (S and PS injury)
  33. Lymphatics
    main or priniciple
    bowel wall, apendices epiploicae, nodules of gerota

    marginal artery and arcades, most numerorsu

    primary colic AA

    • IMA, SMA
    • >paraaortic chain>cisterna chyli
  34. lymph upper 2/3 rectum
    IM nodes>paraaortic nodes
  35. lymph drain lower 1/3 rectum
    sup hem A>IMA

    middle hem A > internal illiac
  36. anal canal lymph drain
    IM > internal illiac

    • inf rectal lymphatics> sup inguinal nodes
    • inf hem A
  37. lymph drain
    5 cm above anal verge
    10 cm
    15 cm
    post vaginal wall, uterus, cervix, broad ligament, fallopian tubes, ovaries cul de sac

    broad ligament, cul de sac

    no spread
  38. Right colon NN
    lower six thoracic > celiac, preaortic, SM ganglia > postganglionic fibers along SMA > r. colon

    R post vagus, celiac plexus > along SMA > r. colon
  39. Left 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
  40. lower 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.
  41. periprostatic plexus
    • subdivision of pelvic plexus
    • on denovilliers f.
  42. sexual function
    ejaculation, inhibition of vasoconstriction

    arteriolar vasodilation
  43. Points of trauma to nn
    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.
  44. IAS motor

  45. levators motor

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

    PR: also gets from inf rectal nn
  46. EAS motor
    s2,s3>inf rectal branch of pudendal n

    perineal branch of S4
  47. anal canal sensation
    • meissners : touch
    • Krause's bulb: cold
    • Golgi-mazzoni bodies: pressure
    • genital corpuscles: friction

    inf rectal branch of pudendal n