TOMOGRAPHY
TONSIL
T
Epiglottis
10th and
9th cranial
nerves
Tonsil
Bitter /
taste
receptor
5th and
7th cranial
nerves
Sour
Sectioned
tongue
Salty
Sweet
tomography An
imaging technique
that
produces a cross-sectional image (“slice”)
of an organ or part of the body. Most
tomography today is performed using
CT scanning
and
MRI,
which produce
accurate and detailed images.
-tomy A suffix denoting the operation
of cutting or making an incision.
tone, muscle The natural tension in the
muscle
fibres. At rest, all muscle fibres
are kept in a state of partial contraction
by nerve impulses from the spinal cord.
Abnormally high muscle tone causes an
increased resistance to movement,
spas-
ticity,
and
rigidity.
Abnormally
low
muscle tone causes floppiness
(see
hypotonia; hypotonia in infants).
tongue A muscular, flexible organ in the
floor of the
mouth
that is composed of a
mass of muscles covered by a
mucous
membrane
. The muscles are attached to
the
mandible
(lower jaw) and
hyoid
bone
above the
larynx
. Tiny nodules called
papillae stick out from the tongue's
upper surface, giving it a rough texture.
Between the papillae at the sides and
base of the tongue are the
taste buds
.
Taste signals are picked up by nerve
fibres from 1 of 4
cranial nerves,
and
impulses then travel to the brain. The
TONGUE
tongue plays an essential part in
masti-
cation
,
swallowing
, and
speech
.
tongue cancer The most serious type of
mouth cancer
due to its rapid spread. It
mainly affects people over 40 and is as-
sociated with
smoking
, heavy alcohol
consumption, and poor oral hygiene. The
edge of the tongue is most commonly
affected. The first sign may be a small
ulcer with a raised margin, a
leukoplakia
,
a fissure, or a raised, hard mass.
Diagnosis of tongue cancer is made by
a
biopsy.
Small tumours,
especially
those occurring at the tip of the tongue,
are usually removed surgically. Larger
tumours or those that have spread
often require
radiotherapy
.
tongue depressor A flat wooden or
metal instrument used to hold the
tongue on the floor of the mouth to
allow examination of the throat.
tongue-tie A minor
mouth
defect, also
known as ankyloglossia, in which the
frenulum (the band of tissue attaching
the underside of the tongue to the floor
of the mouth) is too short and extends
forwards to the tip of the tongue. There
are usually no symptoms apart from lim-
ited movement of the tongue. Rarely,
the condition causes a speech defect,
and a minor operation is required to
divide the frenulum.
tonic One of a diverse group of reme-
dies intended to relieve symptoms such
as malaise, lethargy, and loss of ap-
petite. Evidence suggests that tonics
mainly have a
placebo
effect. The term
tonic is also used adjectivally to relate
to muscle tone (see
tone, muscle),
as in
the tonic neck reflex, one of the primi-
tive
reflexes
found in newborn infants.
tonometry The procedure for measur-
ing the pressure of the fluid within the
eye
, usually performed by an ophthal-
mologist during an eye examination (see
eye, examination of
). Tonometry is use-
ful in diagnosing
glaucoma
.
tonsil One of a pair of oval tissue masses
at the back of the throat on either side.
The tonsils are made up of lymphoid
tissue and form part of the
lymphatic
system
. Along with the
adenoids
, at the
base of the tongue, the tonsils protect
against upper respiratory tract infec-
tions. The tonsils gradually enlarge
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