MouthA cow has no upper front teeth. Its lower incisors bite against a hard dental pad, and its tongue wraps round the grass and tears it off.
EsophagusThe tube from the mouth to the stomach. In a ruminant it works both ways: it also carries the cud back up to be chewed again.
RumenThe largest compartment, also called the paunch. It fills most of the left side and works as a fermentation vat, where microbes break down the plant fiber.
ReticulumThe small front pouch, called the honeycomb for its lining. It lies against the diaphragm, and heavy objects a cow swallows settle in it.
OmasumA round compartment packed with leaves of tissue like a book's pages. It takes up water from the feed. It is also called the manyplies.
AbomasumThe true stomach, most like that of a pig or a person. It is the only compartment lined with glands, which make acid and digestive enzymes.
Small intestineA long tube in three parts: duodenum, jejunum and ileum. Most of the nutrients are absorbed here.
CecumA large blind pouch where the small intestine meets the large. It does little in a ruminant, unlike in a horse.
Large intestineThe last part of the tract. Its main job is to take water back from what passes through. Most of it is the colon.
RectumThe end of the large intestine. What is left of the feed leaves the body from here.
Inside the stomach 8
Dorsal sacThe upper of the two main sacs of the rumen. The gas made by fermentation rises to the top of it.
Ventral sacThe lower of the two main sacs of the rumen. The rumen also ends in two smaller blind sacs at the rear.
PillarsThick folds of muscle that stand in from the wall. They divide the rumen into its sacs.
PapillaeSmall finger-like projections that cover the lining of the rumen. They add surface for taking up the products of fermentation.
Honeycomb liningThe lining of the reticulum. Its ridges form a pattern of six-sided cells, like a honeycomb.
Reticular grooveA channel formed by folds of muscle, also called the esophageal groove. In a calf it carries milk past the rumen and reticulum.
Leaves of the omasumThe many thin folds that fill the omasum like a book's pages. They add surface for taking up water.
DuodenumThe first part of the small intestine, leaving the abomasum. Bile and the juice of the pancreas are added to the feed here.
How this list was compiled: Every name checked on 2026-09-30 in two sources. Mississippi State University Extension, Understanding the Ruminant Animal Digestive System: the whole tract, the four compartments and their linings, the sacs and pillars of the rumen, the reticular groove, https://extension.msstate.edu/publications/understanding-the-ruminant-animal-digestive-system. University of Minnesota Extension, The ruminant digestive system: the four compartments and their everyday names, papillae, leaves, the esophageal groove, https://extension.umn.edu/dairy-nutrition/ruminant-digestive-system. Wikipedia, Ruminant, Rumen, Reticulum, Omasum and Abomasum, https://en.wikipedia.org/wiki/Ruminant. S. Sisson, The Anatomy of the Domestic Animals (1914, public domain), the ox, for where each compartment lies, https://archive.org/details/anatomyofdomesti00siss. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
This cattle digestive system diagram shows the tract inside a cow, then the stomach enlarged and opened. It is a plan: the omasum and abomasum lie on the cow's right side and are moved into view.
Read the full guide
In the cow
Here is the cow digestive system labeled in order: mouth, esophagus, the stomach's compartments, small intestine, cecum, large intestine, rectum. Feed goes to the rumen and reticulum first, which work as one. It then passes through the omasum to the abomasum.
Inside the stomach
Switch to Inside the stomach to see the four parts of a cow's stomach opened: the two sacs of the rumen with the pillars between them, the honeycomb lining of the reticulum and the leaves of the omasum. Press Quiz me to name each part yourself.
Rumen, reticulum, omasum, abomasum: the everyday names, in the same order, are paunch, honeycomb, manyplies and true stomach.
Questions and answers
Does a cow have four stomachs?
It has one stomach with four compartments: the rumen, the reticulum, the omasum and the abomasum. Only the abomasum works like the stomach of a pig or a person.
Why do cows chew cud?
A cow swallows its feed after little chewing. Later it brings soft wads of it, the cud, back up to chew again and mix with saliva. That makes the feed easier for the microbes of the rumen to break down.
How big is a cow's rumen?
It is the largest compartment. One extension service gives 25 gallons or more, depending on the size of the cow; another gives up to 40 gallons for a mature cow.
Do deer and giraffes have the same stomach?
Yes. Cattle, sheep, goats, deer, giraffes and antelope are all ruminants with the same four compartments. Camels and llamas also chew cud, but they are not classed as ruminants.