The Ruminant Stomach

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Ruminant Stomach
Ruminant stomach

The ruminant stomach is a four-chambered organ found in ruminants. It is composed of four separate chambers and allows digestion of large quantities of plant matter that would be relatively indigestible for most other mammals.

Ruminants are mammals that chew cud, that is, the "ruminate." Such animals include many members of the order Artiodactyla, such as buffalo, cattle, goats, sheep, bison, yaks, water buffalo, antelope, deer, giraffes, and camelids (but not pigs). Kangaroos and certain other Australian marsupials also ruminate. Camelids (camels, alpacas, and llamas) ruminate, but have three-chambered stomachs. The stomach of a pig is simple like that of a human being except for the presence of a small pouch or diverticulum at its cardiac end (picture).

A ruminant begins by chewing and swallowing its food. The ingested matter is then softened within the first two chambers of the stomach, the rumen and reticulum, which communicate freely with each other (considered as a single unit, these two chambers are called the "reticulorumen"). Microbes convert the food, particularly cellulose, into less indigestible substances.

The animal regurgitates the partially digested solids ("cud"), and chews them again (the re-chewing of the cud to further break down the semi-digested food is called "ruminating"). It then re-swallows the cud.

The liquid portion of the material within the reticulorumen, passes on to the next chamber, the omasum. Here, water and minerals are absorbed into the blood. The remaining matter moves into the fourth chamber, the abomasum, which is equivalent to the ordinary stomach found in non-ruminants.

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