What does abomasum mean?
The abomasum is the fourth and last of the four chambers that make up the stomach of a ruminant — an animal such as a cow, sheep, or goat that regurgitates and re-chews partially digested food. While the earlier chambers (the rumen, reticulum, and omasum) are devoted to fermenting fibrous plant matter with the help of microbes and absorbing nutrients and water, the abomasum functions much like the human stomach: it secretes hydrochloric acid and digestive enzymes such as pepsin to break down proteins chemically. For this reason it is often called the 'true' or 'glandular' stomach. In veterinary practice, conditions affecting this organ are significant, particularly in dairy cattle, where a 'displaced abomasum' is a well-known post-calving disorder. The word derives from Latin and appears chiefly in scientific, agricultural, and veterinary contexts rather than casual speech.
nounThe fourth and final chamber of the stomach of a ruminant, in which food is digested by acid and enzymes in a manner comparable to the single stomach of monogastric animals.
- The fourth and glandular stomach chamber of ruminants, where acidic and enzymatic digestion takes place.
"In the calf, milk bypasses the rumen and reticulum and passes directly into the abomasum, where true digestion begins."
"The veterinarian diagnosed a displaced abomasum in the dairy cow shortly after calving."
"Food passes from the rumen through the reticulum and omasum before reaching the abomasum."
The Latin-style plural 'abomasa' is preferred in formal scientific and veterinary writing; 'abomasums' is an acceptable anglicized alternative seen less frequently.
"Histological sections of the abomasa were compared across the three species."
Cows have four stomach chambers, but only one of them — the abomasum — does what you'd call 'real' digesting; it's the reason calves can be fed rennet to make cheese.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of abomasum
The word abomasum comes from New Latin, formed from the Latin prefix ab- ('away from') combined with omasum, the name of the third ruminant stomach chamber, whose own origin is uncertain but may relate to Latin omentum ('caul' or fatty membrane). The prefix reflects the chamber's position as the compartment following, or set apart from, the omasum in the digestive tract. English adopted the term by the early 17th century as anatomical writing on animals expanded during that period. It shares its Latinate roots with related anatomical terms such as omasum and with the derived adjective abomasal.
Related word forms
How abomasum is actually used
A technical term used mainly in veterinary medicine, animal husbandry, zoology, and comparative anatomy rather than everyday conversation. It is typically pluralized as 'abomasa' in formal scientific writing, though 'abomasums' also occurs. The related adjective is 'abomasal'.
Easily confused with abomasum
The omasum is the third stomach chamber of a ruminant concerned with water absorption, whereas the abomasum is the fourth chamber where acid and enzymatic digestion occur.