Jo Marie

• Parts of the colon


  • Caecum
  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid colon
  • Rectum
  • Anal canal
• Omental appendices


  • Small, fatty omentum-like projections
• Types of mesocolon


  • Mesocolic: transverse & sigmoid mesocolon attach
  • Omental: omental appendices attach
  • Free: nothing attached
• Taeniae coli


  • Thickened bands of smooth muscle
• Haustra


  • Sacculations of wall of colon between taeniae
• Caecum


  First part of large intestine, continuous with ascending colon, lies in right iliac fossa inferior to junction of terminal ileum and caecum
• Appendix


  Intestinal diverticulum arising from posteromedial aspect of caecum inferior to ileocaecal junction, attached to caecum and proximal part by mesoappendix
• Arterial supply to caecum and appendix


  • Ileocolic artery (terminal branch of superior mesenteric artery)
  • Appendicular artery (branch of ileocolic artery)
• Venous drainage of caecum and appendix

  • Ileocolic vein → superior mesenteric vein
• Lymphatic drainage of caecum and appendix


  • Ileocolic lymph nodes
  • Superior mesenteric nodes
• Innervation of caecum and appendix


  • Sympathetic: lower thoracic
  • Parasympathetic: vagus nerves
  • Superior mesenteric plexus
• Ascending colon


  First part of large intestine, continuous with caecum, lies in right iliac fossa
• Arterial supply to ascending colon


  • Ileocolic artery
  • Right colic artery
  • Anterior cecal artery
  • Posterior cecal artery
• Venous drainage of ascending colon


  • Ileocolic vein
  • Right colic vein
• Lymphatic drainage of ascending colon


  • Epicolic and paracolic nodes
  • Ileocolic and intermediate right colic nodes
  • Superior mesenteric nodes
• Innervation of ascending colon

  • Superior mesenteric nerve plexus
• Transverse colon


  Crosses the abdomen from right colic flexure to left colic flexure, suspended from transverse mesocolon
• Arterial supply to transverse colon

  • Middle colic artery (from superior mesenteric artery)
• Venous drainage of transverse colon

  • Superior mesenteric vein
• Lymphatic drainage of transverse colon


  • Middle colic nodes
  • Superior mesenteric nodes
• Innervation of transverse colon

  • Superior mesenteric plexus
• Descending colon


  Descends past lateral border of left kidney to left iliac fossa
• Arterial supply to descending colon

  • Left colic artery
• Venous drainage of descending colon


  • Inferior mesenteric vein → splenic vein → portal vein
• Lymphatic drainage of descending colon


  • Epicolic and paracolic nodes
  • Intermediate colic nodes
  • Inferior mesenteric nodes
• Innervation of descending colon


  • Sympathetic: lumbar part of sympathetic trunk via lumbar splanchnic nerves, superior mesenteric plexus
  • Parasympathetic: pelvic splanchnic nerves via inferior hypogastric plexus
• Sigmoid colon


  Extends from left iliac fossa to rectosigmoid junction, has an inverted V-shaped attachment to posterior abdominal wall
• Arterial supply to sigmoid colon


  • Left colic artery
  • Sigmoid arteries (from inferior mesenteric artery)
• Venous drainage of sigmoid colon


  • Inferior mesenteric vein → splenic vein → portal vein
• Lymphatic drainage of sigmoid colon


  • Epicolic and paracolic nodes
  • Intermediate colic nodes
  • Inferior mesenteric nodes
• Innervation of sigmoid colon


  • Sympathetic: lumbar part of sympathetic trunk via lumbar splanchnic nerves
  • Parasympathetic: pelvic splanchnic nerves via inferior hypogastric plexus
• Rectum


  Pelvic part of the large intestine, follows curve of sacrum, ends at anorectal flexure
• Arterial supply to rectum

  • Superior rectal artery (from inferior mesenteric artery)
  • Middle rectal arteries
  • Inferior rectal arteries (from internal pudendal artery)
• Venous drainage of rectum


  • Superior, middle and inferior rectal veins (portocaval anastomosis)
• Nerve supply to rectum


  • Sympathetic: hypogastric/pelvic plexus
  • Parasympathetic: S2-S4 spinal cord via pelvic splanchnic nerves
• Lymphatic drainage of rectum


  • Afferents: superior half - pararectal nodes, inferior half - sacral nodes
  • Efferents: superior half - inferior mesenteric nodes, inferior half - internal iliac nodes
• Anal canal


  Inferior elongation of rectum, runs posterior and inferior to pelvic organs
• Structures related to anal canal


  • Anococcygeal raphe (posterior)
  • Ischio-anal fossae (lateral)
  • Perineal body, urogenital diaphragm, membranous urethra, bulb of penis (males - anterior)
  • Perineal body, urogenital diaphragm, lower part of vagina (females - anterior)
• External anal sphincter


  • Striated muscle that surrounds lower part of anal canal, has superficial, deep and subcutaneous parts
• Internal anal sphincter


  • Thickened circular smooth muscle layer that surrounds upper part of anal canal