How Many Stomachs Does a Cow Have?

The basic answer that most people look for from this question is that a cow (or any other bovine such as a bull, a steer, a heifer, or even a bison or buffalo) has FOUR stomachs. However, physiologically speaking, a cow does not have four stomachs; it has four digestive compartments within their single stomach.

The four digestive compartments in order are:
Reticulum (the hardware stomach, where foreign objects collect that cannot pass through the digestive system; this compartment is also responsible for further breakdown processes from the rumen, and is the compartment where partly digested feed is collected to be regurgitated as cud.)
Rumen (where bacteria and protozoa break down cellulose, hemi-cellulose, lignin and fibre from plant material; this is where the process of fermentation takes place)
Omasum (absorbs water and digestible nutrients)
Abomasum (which would be the true stomach, as it is in humans)

One thing that should be noted is that because the abomasum is considered to be the true stomach (and the only functional stomach compartment when a calf, a newborn bovine, is born), the other three compartments are simply an extension of the esophagus. Thus the primary reason that a bovine only has one stomach and not four. The definition of a stomach is that it is an organ which secretes enzymes, acids and other digestive compounds which enable the ability to break down food to mere molecules. Since a cow does not have four of these types of stomachs, it is safe to say that, physiologically, a cow or any other ruminant only has one stomach with four compartments.
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