- Taste buds on the sides of the tongue are con-
centrated to detect sour and salt. - Taste buds at the back of the tongue are con-
centrated to detect bitter.
Three CRANIAL NERVES—the 7th (facial), 9th
(glossopharyngeal), and 10th (vagus)—carry
nerve impulses related to taste to the brain. At its
most primitive level, taste helps the brain deter-
mine what is safe and what is hazardous to eat.
Sweet substances generally contain sugars and
carbohydrates, essential nutrients for energy,
whereas bitter substances may contain acids or
chemicals that are potentially harmful. Recent
research indicates that gustation is far more com-
plex than simple delineation among taste buds,
however, with some scientists speculating that
taste represents learned interpretations as much as
response to specific qualities. Further, taste and
smell are inextricably intertwined. Though distinct
nerve impulses from each reach the brain, the
brain analyzes them and creates collective inter-
pretations.
The functions of breathing and swallowing share
the structures of the throat. The chamber at the
back of the mouth and the top of the throat is the
pharynx; it receives both air and food. A flap of car-
tilage at the base of the pharynx, the epiglottis,
closes across the TRACHEA when swallowing and
opens to allow the passage of air during inhalation
and exhalation. The small flap of tissue that hangs
visibly at the back of the throat, the uvula, is an
extension of the soft palate. Doctors are uncertain
of the uvula’s function; it may help keep swallowed
food from entering the nasal passages.
The larynx is a sequence of connected cartilage
structures that makes speech possible. Air passing
through the larynx causes these cartilages and the
folds of tissue known as the VOCAL CORDS to
vibrate, generating sounds. The muscles of the
throat help move the sound vibrations into the
mouth, which then forms them into noises and
words. Hearing further helps shape speech, pro-
viding instant auditory feedback. It is difficult,
although not impossible, for someone who has
profound HEARING LOSSto speak clearly enough for
others to understand. STROKEand neuromuscular
disorders such as PARKINSON’S DISEASEare among
the common causes of dysfunctions affecting swal-
lowing and speech.Health and Disorders of the Ears, Nose,
Mouth, and Throat
Disorders and dysfunctions of the ears, nose,
mouth, and throat range from structural defects
present at birth to infections to trauma resulting
from ACCIDENTAL INJURIES or diseases such as
CANCER. Disturbances of taste, smell, hearing, and
balance may accompany numerous health condi-
tions from COLDSto DIABETES, stroke, and Parkin-
son’s disease. Health experts estimate that about 2
million Americans have diminished, altered, or
lost functions of taste and smell. More than 28
million have a perceptible loss of hearing ability; 2
million of them are profoundly deaf (unable to
hear at a functional level). Disturbances of balance
resulting from dysfunctions of the inner ear affect
as many as 45 million Americans.
Nearly everyone experiences the most frequent
health condition that affects the chemosenses
simultaneously: the common cold. Its familiar
symptoms include nasal congestion and runny
nose (RHINORRHEA), sore throat (PHARYNGITIS), and
the sensation of “stuffy” ears and muffled hearing
(and sometimes dizziness, when the congestion
alters the inner ear’s balance mechanisms). This
choreography of discomfort results from the inti-
mate integration of both structure and function of
these senses.
Limiting or avoiding exposure to loud noise
could protect millions of people from hearing loss.
Surgical and technological advances hold great
promise for restoring some kinds of hearing loss.
Though some diminishment occurs naturally with
aging, hearing, taste, and smell require minimal
effort to maintain healthy function across the
spectrum of age.Traditions in Medical History
Before the advent of ANTIBIOTIC MEDICATIONSand
vaccines in the middle of the 20th century, many of
today’s commonplace ailments involving the ears,
nose, mouth, and throat were serious and even life-
threatening illnesses. Otitis media (middle ear
infection), though less common or perhaps simply
less frequently diagnosed 50 years ago than it isThe Ear, Nose, Mouth, and Throat 5