Large Intestine - Anatomy & Physiology

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Introduction

The large intestine extends from the ileum of the small intestine to the anus. It absorbs water from the ingesta and stores faeces prior to defeacation. Every species has a large microbial population living in the large intestine, which is of particular importance to the hindgut fermenters. For this reason, hindgut fermenters have a more complex large intestine with highly specialised regions for fermentation.

The large intestine can be divided into:

• Caecum
• Colon
• Rectum

Innervation

• Like the small intestine, the large intestine recieves sympathetic and parasympathetic innervation.
• Neurones interact with the myenteric plexus to affect contractility, and with the submucosal plexus to affect secretions.
  • The sympathetic have coeliac, cranial mesenteric and caudal mesenteric ganglia.
  • As the sympathetic fibres leave the ganglia, they surround their respective artery.
  • Parasympathetic innervation stimulates peristalsis.

Histology

• The muscosa of the large intestine is smooth; there are no villi.
• There are numerous scattered lymph nodules.
• Taenia may be present.

Species Differences

Pig

• Taenia present

Links

Pathology of the Small and Large Intestine