The Large Intestine: Introduction and Index

The large intestine is the last attraction in digestive tube and the location of the terminal phases of digestion. In comparison to other regions of the tube, there are huge differences among species in the relative size and complexity of the large intestine. Nonetheless, in all species it functions in three processes:

• Recovery of water and electrolytes from ingesta: By the time ingesta reaches the terminal ileum, roughly 90% of its water has been absorbed, but considerable water and electrolytes like sodium and chloride remain and must be recovered by absorption in the large gut.
• Formation and storage of feces: As ingesta is moved through the large intestine, it is dehydrated, mixed with bacteria and mucus, and formed into feces. The craftsmanship (for want of a better term) with which this is carried out varies among species.
• Microbial fermentation: The large intestine of all species teems with microbial life. Those microbes produce enzymes capable of digesting many of molecules that to vertebrates are indigestible, cellulose being a premier example. The extent and benefit of fermentation also varies greatly among species.

Core concepts in physiology of the large intestine are presented as the following topics:

• Gross and Microscopic Anatomy of the Large Intestine
• Absorption and Secretion, and Formation of Feces in the Large Intestine
• Large Intestinal Motility
• Microbial Fermentation

Advanced and supplemental topics related to physiology of the large intestine:

• Intestinal Gas Production
• Beans, Beans, the More We Eat ...

Pathophysiology and diseases affecting the large intestine:

• The Gastrointestinal Barrier
• Pathophysiology of Diarrhea

Send comments to Richard.Bowen@colostate.edu