Caecum - Anatomy & Physiology

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ALIMENTARY SYSTEM
LARGE INTESTINE



Introduction

Dog caecum, ileum and colon - © RVC 2008
Gibbon caecum and appendix- © RVC 2008

The caecum is a blind ending diverticulum of the large intestine and it exists at the junction of the ileum and the ascending colon. It's size and physiological importance vary between species. It is a site of microbial fermentation, absorption and transportation.

Structure

  • It communicates with the ileum via the ileal orifice and with the colon via the caecocolic orifice.
  • It consists of a base, body and apex, the apex being the blind-ending portion.
  • It is attached to the ileum by a fold of peritoneum called the ileocaecal fold.

Function

Microbial Fermentation

Absorption

  • VFAs that are produced are absorbed here.

Transportation

  • Segmental contractions facilitate absorption and microbial actitivity.
  • Every 3-5 minutes, segmentation is replaced by mass movements. This is similar to peristalsis, but large portions of the caecum contract simultaneously to move chyme into the colon.

Histology

  • No villi
  • Mucosa has mucous glands
  • Lamina muscularis has large lymphatic nodules.
  • Submucosa has no glands.

Species Differences

Canine

  • On the right side of the abdomen.
  • Unique because it has no direct connection to the ileum.
  • Short and held in a spiral shape against the ileum by the ileocaecal fold.
  • Little microbial fermentation takes place.

Ruminant

  • On the right side of the abdomen in the supraomental recess
  • The apex points caudally.
  • Relatively small and featureless: there are no taenia or haustra.
  • Some microbial fermentation takes place.

Equine

  • A significant amount of fermentation takes place.

Porcine

  • On the left side of the abdomen, with the apex pointing caudoventrally.
  • Cylindrical in shape.
  • Three taenia are present
    • The ventral taenia provides the attachment for the ileocaecal fold.
    • The lateral and medial taenia are free.

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