EAR
EARACHE
ea r The organ of
hearing
and
balance.
It
consists of three parts: the outer ear,
the middle ear, and the inner ear.
The outer ear comprises the
pinna
and
the ear canal. The outer part of the ear
canal produces
earwax,
which traps
dust and foreign bodies. The canal is
closed at its inner end by the
eardrum,
which vibrates in response to changes
in air pressure that make sound.
The middle ear is a cavity that con-
ducts sound to the inner ear by means
of three tiny, linked, movable bones
known as
ossicles.
The first bone, the
malleus, is joined to the inner surface
of the eardrum. The second, the incus,
is linked to the malleus and to the third
bone, the stapes. The base of the stapes
fills the oval window leading to the
inner ear. The
eustachian tube
links the
middle ear to the back of the nose.
The inner ear is an intricate series of
structures deep within the skull. The
front part, the
cochlea
, is a tube con-
taining nerve fibres that detect different
sound frequencies. The rear part of the
inner ear contains three semicircular
canals and is concerned with balance.
The semicircular canals are connected
to a cavity called the
vestibule
and con-
tain hair cells bathed in fluid. Some of
these cells are sensitive to gravity and
acceleration; others detect direction of
movement. Information from the inner
ear is conducted to the brain via the
vestibu locochlear nerve.
earach e Pain in the ear. Earache is a
common symptom, especially in child-
hood. The most frequent cause is acute
otitis m edia
, which results in severe,
stabbing pain. Another common cause
of earache is
otitis externa.
The pain may
be accompanied by irritation and a dis-
charge of
pus
. Intermittent earache may
accompany dental problems,
tonsillitis
,
throat cancer (see
pharynx, cancer
of),
or pain in the jaw or neck muscles.
EAR
ear. Inner ear
Skull
bone
Outer
ear
Stapes
Semicircular
canals
Incus
Malleus
PARTS OF
nerve
Eardrum
Cochlea
Muscle .
Cartilage
Pinna
Oval
window
Eustachian
/
tube
Cut edge
of cochlea
Ear canal
188
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