Cecum

The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix, to which it is joined). The word cecum stems from the Latin 'caecus' (blind).

It receives chyme from the ileum, and connects to the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve (ICV) or Bauhin's valve. It is also separated from the colon by the cecocolic junction. While the cecum is usually intraperitoneal, the ascending colon is retroperitoneal.

In herbivores, the cecum stores food material where bacteria are able to break down the cellulose. This function no longer occurs in the human cecum (see appendix), so in humans it is simply a dead-end pouch forming a part of the large intestine.

Its anatomy varies significantly across domestic species due to dietary and digestive adaptations.

Here’s an overview of cecal anatomy in major domestic animals:

1. Horses

• Size & Shape: Very large, comma-shaped, and sacculated.

• Location: Lies mainly on the right side of the abdomen.

• Capacity: Can hold up to 30–35 liters.

• Anatomical Parts:

  • Base: Fixed to the dorsal body wall.

  • Body: Extends ventrally.

  • Apex: Points cranially and to the left.

• Function: Major site of microbial fermentation of cellulose; very important in hindgut digestion.

2. Ruminants (Cattle, Sheep, Goats)

• Size & Shape: Moderately developed; less prominent than in horses.

• Location: Right side of the abdominal cavity.

• Structure: Not sacculated; relatively simple in shape.

• Function: Minor role in fermentation compared to the forestomachs (rumen, reticulum).

3. Pigs

• Size & Shape: Large, coiled spiral shape.

• Location: Caudal and left side of the abdominal cavity.

• Structure: Spiral colon arises from the cecum; well developed for fermentation.

• Function: Important in fermentation; pigs are omnivores, so the cecum is adapted to digest some fibrous material.

4. Dogs and Cats

• Size & Shape: Small, tubular, and simple.

• Location: Right side, at the junction of ileum and colon.

• Function: Minimal; non-fermentative role due to their carnivorous diet.

5. Birds (e.g., Chickens)

• Structure: Paired ceca (right and left).

• Location: At the junction of the small and large intestines.

• Function: Fermentation, water absorption, and immune function.

Summary of Functions

• Fermentation: Especially in horses and pigs; microbial breakdown of cellulose.

• Water and Electrolyte Absorption: Common in all species.

• Immunological Role: Contains lymphoid tissue contributing to gut immunity.