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Infracolic Compartment: Large Bowel (Subdivisions (Anal Canal (feature:…

- - - - 3 narrow bands (libre, omentalis, mesocolica)
      - equidistant around tube from appendix to rectum
      - end: expand & fuse w/ one another --> more robust, distinct layer
      - 1/6 shorter than colon
        
        haustra coli
      - thinner muscular layers; incomplete outer (long.) layer
    - - fat storage bodies
      - enclosed & suspended w/in peritoneum
    - - remove water from food residue
      - store & compact stool
- - - - terminal ileum invaginates into cecum --> superior & inferior lips
      - not competent; contraction of terminal ileum prevents reflux of cecal contents into ileum
    - - blind-ending diverticulum
      - ~ 8 cm long
      - retrocecal position (64%)
      - taenia coli form complete long. layer
      - mucosa & submucosa filled w/ lymphoid nodules
      - Appendicitis
        
        inflammation d/t blockage of lumen
        
        overgrowth of epithelial lining
        
        impaction via coprolith (fecal stone)
        
        referred pain: GVA fibers to T10 dermatome @ umbilicus
        
        McBurney's point: contact w/ parietal peritoneum of post. body wall (2/3 distance from umbilicus to ASIS)
  - - - anterior: SI & greater omentum
      - lateral: (R. paracolic gutter &) transversus abdominis
      - medial: post. body wall & SI
      - posterior: post. body wall & R. kidney
  - - - gastrocolic lig. to stomach
      - posterior: mesocolon to post. body wall
      - anterior: omental apron of greater omentum
      - phrenicocolic lig.: L. colic flexure to L. diaphragm
    - - superior: liver, gall bladder, stomach & spleen
      - anterior: ant. body wall
      - inferior: SI
      - posterior: mesocolon
  - - - anterior: SI
      - lateral: (L. paracolic gutter &) transversus abdominus
      - medial: SI & L. kidney
      - posterior: post. body wall
  - - - evaginations of colonic mucosa at weakest pts (where blood vessels penetrate)
      - most often in descending & sigmoid colon
      - d/t increased pressure generated by colon to move feces of low fiber content
      - diverticulitis: when material becomes lodged in pockets causing inflammation
  - - - proximal 1/3: peritoneum laterally & anteriorly
      - mid 1/3: peritoneum anteriorly only
      - distal 1/3
        
        rectal ampulla: dilated portion resting on pelvic diaphragm; exists below peritoneum
        
        peritoneum reflected to pelvic visceral or lateral & post. pelvic wall
    - - outer long.: teniae coli fan out --> bands ant. & post.
      - inner circ.: continuous w/ colon
    - - 3 shelves (mucosa, submucosa & some circular m.)
      - protrude from walls of rectum
      - cause external curvatures & flexures (L=2; R=1)
      - assist in supporting fecal mass
    - - dilated portion superior to pelvic diaphragm
  - - - anal sphincters:
        
        internal (IAS)
        
        involuntary; autonomically innervated
        
        continuous w/ inner circ. layer
        
        external (EAS)
        
        circularly arranged skeletal m.
        
        inferior rectal bbr. of pudendal n. (S2-4)
      - anal columns:
        
        vertical folds d/t veins deep to mucous membrane
      - anal valves:
        
        venous anastomses connect base of contiguous anal columns & bridge across anal sinuses; course creates pectinate line
      - anal sinuses:
        
        depression b/w anal columns & valves
      - Hilton's White Line (intersphincteric line)
        
        pt where EAS meets IAS
        
        anal verge: transitional epithelium changes to perianal skin
      - Transitional area (anal pecten)
        
        pectinate line above & Hilton's White line below
        
        demarcates epithelial change of mucosa
    - - internal
        
        prolapse of rectal mucosa
        
        internal rectal venous plexus affected; trapped by contracted sphincters --> engorged & ulcerated veins
        
        bright red blood d/t elaborate anastomoses
      - external
        
        thrombosed vv. of external rectal venous plexus
        
        directly under skin; painful
      - d/t increased intra-abdominal pressure (i.e. chronic constipation, straining at stool; pregnancy & portal HTN)