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Large Bowel

Aug 24, 20252 min read

Diseases of Large bowel

Dr. M. Almadani

Presentations

Principles and Practice of Surgery

Pg 234-262Z

Anatomy & Features

  • The colon is a 5-6-ft long, inverted, U-shaped.

Cecum (and appendix) and ano-rectum,

which are parts of the large intestine, are not included in the colon.

MAYO FOUNDATION FOR MEDICAL EDUCATION AND RESEARCH, ALL RIGHTS RESERVED.

Ascending colon

  • Starts from a proximal blind end (pouch) called the cecum.
  • The ascending colon takes a right-angled turn just below the liver (hepatic flexure) and becomes the transverse colon

Transverse colon

  • Has a horizontal course from right to left, occupying the right hypochondrium, epigastrium, and left hypochondrium.
  • At splenic flexure, it is attached to the diaphragm by the phrenocolic ligament) and becomes the descending colon,
  • Splenic flexure is higher (cranial) to hepatic flexure.

Descending colon:

  • leads to the inverted V-shaped sigmoid colon, which then becomes the rectum at the S3 level

  • Ascending, & descending parts of the colon are retroperitoneal

  • The transverse colon and the sigmoid colon have a mesentery

  • Cecum is intraperitoneal but uses the mesentery of the ileum.

Teniae coli

are present in large bowel, but not present in the rectum.

  • Appendages of fat, containing small blood vessels, called omental
  • appendages (appendices epiploicae) are attached to colon.

Paracolic gutters

  • Lateral to ascending and descending colon are the right and left gutters of the peritoneal cavity,
  • Fluid/pus in the upper abdomen can trickle down into the pelvic cavity.

Blood supply

  • Superior mesenteric artery through its right colic and middle colic branches
  • Inferior mesenteric artery through its left colic and multiple sigmoid branches.
  • Vasa recta are terminal branches of these arteries entering the colonic wall

The colon has 4 layers:

  1. Mucosa:

    • Columnar epithelium with a large number of mucus secreting goblet cells
    • No villi,

  2. Submucosa

    • Contains the blood vessels and Meissner nerve plexus.

  3. Muscularis propria

    • Contains the inner circular and outer longitudinal
    • Muscles and myenteric (Auerbach) nerve plexus

  4. Serosa

    • visceral peritoneum.

Right hemicolectomy:

  • Includes the removal of a few centimeters of terminal ileum, cecum (with appendix), ascending colon, & proximal transverse colon
  • Ileotransverse anastomosis

Left hemicolectomy

  • Includes the removal of the distal transverse colon, descending colon, and sigmoid colon
  • Colorectal anastomosis

Total colectomy

  • Includes removal of the cecum (with appendix), ascending colon, transverse colon, descending colon, and sigmoid colon
  • Ileorectal anastomosis

1 right 2, 3 left 4, 5 total

Graph View

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