navelA popular term for the umbilicus,
the depression in the abdomen that
marks the point at which the umbilical
cord was attached to the fetus.
nebulizerAn aerosol device used to ad-
minister a drug in the form of a fine mist
for inhalation through a face mask or
mouthpiece. Nebulizers are used to ad-
minister bronchodilator drugs, especially
in the emergency treatment of asthma.
neckThe part of the body that supports
the head and serves as a passageway bet-
ween the head and brain and the body.
The neck contains many important
structures: the spinal cord(which carries
nerve impulses to and from the brain);
the trachea(windpipe); the larynx(voice
box); the oesophagus; the thyroidand
parathyroid glands; lymph nodes; and
severalmajor blood vessels. The upper 7
vertebrae of the spine are in the neck; a
complex system of muscles is connected
to these vertebrae, the clavicles (collar-
bones), the upper ribs, and lower jaw.
Neck disorders include torticollis(wry
neck) in which the head is twisted to one
side. Fracturesand dislocationsof verte-
brae in the neck and whiplash injurycan
injure the spinal cord causing paralysis
or even death (see spinal injury). Any con-
dition causing swelling in the neck may
interfere with breathing or swallowing.
Degeneration of the joints between the
neck vertebrae may occur due to cervical
osteoarthritis, causing similar symptoms
to those of disc prolapse. In ankylosing
spondylitis, fusion of the vertebrae may
result in permanent neck rigidity. Cervi-
cal ribis a rare congenital defect in which
there is a small extra rib in the neck.
Neck pain of unknown origin is very
common. As long as neurological symp-
toms (such as loss of sensation or
muscle power) are absent, the condi-
tion is unlikely to be serious and
usually disappears within a few weeks.
neck dissection, radicalA surgical
procedure for the removal of cancerous
lymph nodesin the neck. The operation
is commonly part of the treatment of
cancer of the tongue, tonsils, or other
structures in the mouth and throat.
neck rigidityMarked stiffness of the
neck caused by spasm of the muscles in
the neck and spine. Neck rigidity is an
important clinical sign of meningitis
(inflammation of the membranes cover-
ing the brain and spinal cord). Severe
neck rigidity may cause the head to arch
backwards, especially in babies.
necrolysis, toxic epidermalA severe,
blistering rash in which the surface
layers of the skin peel off, exposing large
areas of red raw skin over the body. The
condition carries a risk of widespread in-
fection and loss of body fluid and salts.
The most common cause of toxic epi-
dermal necrolysis is an adverse reaction
to a drug, particularly a barbiturate,
sulphonamide, or penicillin. The cond-
ition usually clears up when the drug is
discontinued. Intravenous fluid replace-
ment is sometimes necessary.
necrophiliaA rare sexual perversion in
which orgasm is achieved by means of
sexual acts with dead bodies.
necropsyA little used alternative medi-
cal term for an autopsy (postmortem
examination of a body).
necrosisThe death of tissue cells. Nec-
rosis can occur as a result of ischaemia
(inadequate blood supply), which may
lead to gangrene; infection, such as tu-
berculosis; or damage by extreme heat
or cold, noxious chemicals, or excessive
exposure to X-rays or other radiation.
In necrosis due to tuberculosis, the
dead tissue is soft, dry, and cheese-like.
Fatty tissue beneath the skin that has
died as a result of damage or infection
develops into tough scar tissue that
may form a firm nodule.
necrotizing fasciitisA rare, serious
infection of tissues beneath the skin by a
type of streptococcal bacterium. Necro-
tizingfasciitis is most likely to occur as
a complication following surgery. The
initial symptoms are inflammation and
blistering of the skin. The infection
spreads very rapidly, and the bacteria
release enzymes and toxins that can
cause extensive destruction of deeper
tissues and damage internal organs.
Urgent treatment with antibiotic drugs
and removal of all infected tissue are ess-
ential. The infection is life-threatening.
needle aspirationSee biopsy.
needle exchangeA health scheme that
enables intravenous drug abusers to
exchange used hypodermic needles forNAVEL NEEDLE EXCHANGE
N