rumen

The anaerobic fermentative fore stomach of ruminants that consists of anatomically and functionally indistinct chambers; important role in the predigestion of the cellulose rich diet of herbivores. In addition to the specialized anatomic pouches, a rich biodiverse population of protists, viruses, fungi, bacteria, and enzymatic cofactors mix with water and alkaline saliva (during rumination) serves as a microenvironment within which volatile fatty acid (VFA) end-products (e.g., butyric acid, valeric acid) are generated (along with by-products such as belched or eructated methane and fine textured ingesta that passes to the rear gut to complete digestion and form feces). Average rumen holds 40 gal or 160 L of ingesta. Compartments include the reticulum and rumen (proper); rumen is compartmentalized by anterior and posterior pillars. Ventral and dorsal coronary pillars divide off the ventral and dorsal blind sacs, and by longitudinal pillars, which divide the main rumen compartment into the dorsal and ventral sacs, as well as the omasum and abomasum (the latter is the true monogastric type stomach).
See also: ruminant.

[L. throat, gullet]