PREFACE TO VOLUME 1
Leading the reader into the four-volume The Facts
On File Encyclopedia of Health and Medicine through
Volume 1 are the structures and functions that
lead the body’s way in the world. These are the
body systems that equip the body to interact with
its external environment. Some people refer to
these as the “interface” systems, drawing from the
concepts and terminology of computers. These
systems allow the body to receive and respond to
sensory input.
The Ear, Nose, Mouth, and ThroatVolume 1’s first section is the “The Ear, Nose,
Mouth, and Throat.” Through these structures the
body receives auditory, olfactory, and gustatory
sensory information—sounds, smells, and tastes.
The throat does double duty as the conduit to
carry both air and nutrition, essential sustenance
for the body, and also makes possible the uniquely
human form of communication—speech.
The functions of these sensory organs and
structures overlap and integrate with each other
in ways such that the loss of one sensory system
affects others. Speech is difficult without the abil-
ity to hear, for example, and the sensory path-
ways for smell and taste are so intertwined that
both networks become impaired when one or the
other does not function properly. Olfactory nerve
fibers are capable of detecting thousands of odors,
enhancing the brain’s ability to interpret hundreds
of flavors with input from only four basic taste
qualities (sweet, sour, salt, and bitter).
The sense of touch resides in specialized nerves
that populate the surface of the skin in varying
concentrations to provide different levels of tactile
response. The lips and fingertips, for example, are
exquisitely sensitive, while the surfaces of the
arms and legs are less responsive to touch. The
structures of the inner ear also regulate the body’s
balance, integrating with the nervous system as
well as the musculoskeletal system (as anyone
who has found it challenging to walk after spin-
ning in circles well knows).The Eyes
Sight is so highly refined in humans that many
people consider it the most important of the five
senses. The structures of vision function inde-
pendently from other sensory structures, though
the brain combines sensory information to
develop complex perspectives about the body’s
placement and function within its external envi-
ronment.
The two eyes work independently as well,
though synchronously. The brain blends and
interprets the information it receives from each
eye to form images that have spatial dimension.
This provides depth perception, which interplays
with proprioception (the body’s sense of its place-
ment within its physical environment) and move-
ment. The loss of vision in one eye requires the
brain to rely more on other sensory input and on
learned responses to help the body navigate in a
dimensional world.The Integumentary System
The structures of the integumentary system—
skin, nails, and hair—cover and protect the body
from the external environment as well as provide
the basis for appearance and identity. Integument
is Latin for “cloak,” an apt term for the system
that envelops the body and literally holds it
together.
The integumentary system provides front-line
defense against infection as a barrier as well as
through immune cells and substances that residexiii