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(vertebrate zoology)
The first chamber of the ruminant stomach. Also known as paunch.



(also paunch), the first and largest section of the four-chambered stomach of ruminants. The rumen occupies almost the entire left half of the abdominal cavity. In adult animals its volume equals four-fifths the volume of the entire stomach. In newborns, which are fed only milk, the rumen is half the size of the abomasum. The first section of the rumen is connected to the reticulum and the esophagus. The rumen’s walls consist of the serous membrane (exterior membrane), the muscular membrane (middle membrane), and the mucous membrane (interior membrane). The interior wall has bands that divide the rumen into sacs, which slow down the movement of food. The interior epithelial surface, except for the bands, has processes, or papillae. In camels and llamas the walls of the rumen have deep cells, in the floors of which open cardiac glands. Such glands are absent in the rumens of other ruminants.

Decomposition of plant substances through bacterial and protozoan activity occurs in the rumen. Volatile acids are assimilated through the surface of the mucous membrane. The food is subjected to the action of enzymes and is mixed. From the rumen the food enters the reticulum or is regurgitated into the mouth, where it is masticated again. The food then passes into the omasum through the esophageal groove.

T. B. SABLINA [22–10101]

References in periodicals archive ?
Badary OA, Al-Shabanah, OA, Nagi MN, Al-Rikabi AC, Elmazar MM (1999) Inhibition of Benzo(a) pyrene induced forestomach carcinogenesis in mice by thymoquinone.
Sparnins and co-workers (81) first showed that AMTS increased the activity of GST in the forestomach, small-bowel mucosa, liver, and lung of mice.
In the NCTR/EPRI study, health risks of coal tar would be based on lung tumor incidence and health risks of BaP would be based on forestomach tumor incidence.
It was shown that Keapl transgenic mouse knockout mutants developed hyperkeratosis in the esophagus and forestomach during gestation, which led to death from malnutrition after birth.
The large surface area of the forestomach and the increased thickness and strength of scaffolds derived from the forestomach allows the isolation of larger ECM scaffolds from the forestomach than is possible from other organs (Ward et al.
Inhibition of benzo (a) pyrene-induced forestomach carcino-genesis in mice by thymoquinone.
Inhibition of benzo(a)pyrene-induced mouse forestomach neoplasia by conjugated dienoic derivates of linoleic acid.
Glutathione S-transferases of female A/J mouse liver and forestomach and their differential induction by anti-carcinogenic organosulfides from garlic.
Enhanced tum from the perspective effect on forestomach and oesophageal squamous epithelium.
When possible, a sample of contents was immediately collected from the forestomach and a crude estimate made of stomach fullness (i.