* 2 colon

• 2.1 ascending colon
  • 2.1.1 right coloic flexure (hepatic flexure)
  • 2.1.2 12.5 cm long
  • 2.1.3 extends from caecum to inferior surface of right lobe of liver
• 2.2 descending colon
  • 2.2.1 25 cm long
  • 2.2.2 left colic flx to sigmoid colon
  • 2.2.3 runs vertically up to iliac crest
• 2.3 transverse colon
  • 2.3.1 left colic flexure (splenic flexure )
  • 2.3.2 50 cm long
  • 2.3.3 suspended by transverse mesocolon
  • 2.3.4 anteriorly related to greater omentum and anterior abd wall
  • 2.3.5 posteriorly to 2nd part of duodenum
• 2.4 sigmoid colon( pelvic colon)
  • 2.4.1 37.5 cm long
  • 2.4.2 extends from pelvic brim to 3rd piece of sacrum
• 3 relevant features
  • 3.1 wider in calibre
  • 3.2 longitudinal muscle coat forms a thin layer ( पतली परत बनाते हैं )
    • 3.2.1 3 ribbon like bands called taenia coli (
      • taenia libera (
        • placed anteriorly ( अग्र परत )
          • ascending colon
          • caecum
          • sigmoid colon
          • descending colon
        • inferiorly
          • transverse colon
      • taenia mesocolica
        • present on posteromedial surface
          • ascending colon
          • caecum
          • sigmoid colon
          • descending colon
        • posteriorly
          • transverse colon
      • taenia omentalis
        • posterolaterally
          • ascending colon
          • caecum
          • sigmoid colon
          • descending colon
        • anteroposterior
          • transverse colon
    • 3.2.2 since taenia is shorter colon is puckered and sacculated
  • 3.3 appendices epiploicae
    • 3.3.1 small bags of peritoneum
    • 3.3.2
  • 3.4 blood supply of colon
    • 3.4.1 marginal artery of drummond
    • 3.4.2 terminal branches of marginal artery
      • vasa longa
      • vasa brevia
  • 3.5 lymph nodes
    • 3.5.1 epicolic lymph nodes
    • 3.5.2 paracolic lymph nodes
    • 3.5.3 intermediate nodes
  • 3.6 epithelium is absorptive (coloumnar ) but villi are absent
• 5 histology of colon
  • 5.1 mucous membrane
    • 5.1.1 invaginations called crypts of leiberkuhn
  • 5.2 submucosa
    • 5.2.1 meissners plexus
    • 5.2.2 solitary lymphoid follicles
  • 5.3 muscularis externa
    • 5.3.1 outer longitudinal coat thickened to form
      • taenia coli
    • 5.3.2 inner coat is circular fibres
    • 5.3.3 outermost layer is serous layer