Digestion is the mechanical and chemical breaking down of food
into smaller components, to a form that can be absorbed, for
instance, into a blood stream. Digestion is a form of
catabolism; a break-down of macro food molecules to smaller
ones. In mammals, food enters the mouth, being chewed by teeth,
with chemical processing beginning with chemicals in the saliva
from the salivary glands. Then it travels down the esophagus
into the stomach, where acid both kills most contaminating
microorganisms and begins mechanical break down of some food (eg
denaturation of protein), and chemical alteration of some. After
some time (typically an hour or two in humans, 4-6 hours in
dogs, somewhat shorter duration in house cats), the results go
through the small intestine, through the large intestine, and
are excreted during defecation. Other organisms use different
mechanisms to digest food. This article is licensed under the
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