Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
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.
See also: ruminant.
[L. throat, gullet]
n. pl. ru·mina (-mə-nə) or ru·mens
The first division of the stomach of a ruminant animal, in which most food collects immediately after being swallowed and from which it is later returned to the mouth as cud for thorough chewing. Also called paunch.
rumena branch of the oesophagus of ruminants in which unchewed food is stored temporarily and from which it is regurgitated to the mouth for chewing (see RUMINANT STOMACH). Some cellulose is digested and absorbed in the rumen and bacterial action results in the synthesis of B vitamins there. Cellulase is produced by bacteria which may number 1 billion per cm3 in the rumen.
pl. rumens, rumina; the largest of the compartments of the forestomach of ruminant animals that serves as a fermentating vat. It is lined by a keratinized epithelium bearing numerous absorptive papillae; it is partly subdivided by folds (pillars). These include dorsal and ventral sacs and a caudodorsal blind sac and a caudoventral blind sac. It communicates directly with the reticulum cranially and has no other exit. It covers most of the floor of the adomen on the left in the nonpregnant animal and in animals not affected by left displacement of the abomasum. Caudally it may reach the brim of the pelvis and is palpable rectally.
see cud transfer.