Summary and Introduction
Digestion is a complex process involving specialized anatomical and
physiological
adaptations for the absorption of nutrients. Its purpose is to prepare
food
for use by
cells and organs throughout the body. Because large food particles cannot
reach cells, the
process of digestion breaks the food down into nutrients that can be
absorbed into the
blood stream and carried to any cell in the body. The methods of digestion
are
mechanical and chemical. Each segment of the digestive system has a
special
design to
perform a unique function that is an essential part of the digestive
process.
Digestion begins in the mouth and is completed at the anus. As food
moves through the digestive tract, it passes through several compartments.
Accessory organs
that produce
digestive enzymes drain their contents into the compartments at different
points along the
way. Each compartment and accessory organ serves a specific function. At
each stage,
the food is transformed into a slightly different form that allows it to be
passed along to
the next compartment. As it moves through the digestive tract, nutrients
and water are
extracted, producing waste. The waste products are eventually
eliminated.
The coordination of functions is complicated. Signaling between the
nervous and
endocrine systems occurs at both the local cellular level as well as
throughout the entire
body. Through the process of digestion, food is transformed from large
complex particles
into basic elements that are then easily absorbed into the blood stream.
