Caecum - Anatomy & Physiology

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Introduction

Dog caecum, ileum and colon - © 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

The contribution of this is species dependant. The products of fermentation are VFAs.

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.

Horse

A significant amount of fermentation takes place.

Pig

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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