CALCANEUS
CALCULUS, URINARY TRACT
C
calcaneus
The heel bone. It is one of the
tarsal bones and is the largest bone in
the
foot.
The
Achilles tendon
is attached
to the back of the calcaneus
.
calciferol
An alternative name for vita-
min D
2
, also known as ergocalciferol
(see
vitamin
D).
calcification
The deposition of
calcium
salts in body tissues that is part of the
normal process of bone and teeth for-
mation and the healing of fractures.
Calcification also occurs in injured mus-
cles, in arteries affected by
atherosclerosis,
and when blood calcium levels are raised
by disorders of the
parathyroid glands.
calcification, dental
The deposition of
calcium
salts in developing teeth. Pri-
mary teeth begin to calcify in a fetus at
between 3 and
6
months gestation; cal-
cification of permanent teeth (other
than the wisdom teeth) begins between
birth and 4 years. Abnormal calcification
occurs in amelogenesis imperfecta, an
inherited disorder of the enamel (see
hypoplasia, enam el
), and can also result
from the absorption of high levels of
fluoride (see
fluorosis
).
calcinosis
The abnormal deposition of
calcium
salts in the skin, muscles, or
connective tissues,
forming
nodules
. The
condition occurs in connective tissue
disorders such as
scleroderma
or
der-
matomyositis
. (See also
calcification.
)
calcipotriol
A derivative of
vitamin D,
used in topical preparations for treating
the skin disorder
psoriasis
.
calcitonin
A
horm one
produced by the
thyroid gland
that helps to control
blood
calcium
levels by slowing loss of
calcium from the bones. A synthetic form
of calcitonin is used in the treatment of
Paget's disease.
Calcitonin is also used
to reduce high blood levels of calcium
in
hypercalcaemia
.
calcium
The body's most abundant min-
eral, essential for cell function, muscle
contraction, the transmission of nerve
impulses, and
blood clotting
. Calcium
phosphate is the hard basic constituent
of teeth and bones. Dietary sources of
calcium include dairy products, eggs,
and green, leafy vegetables. Calcium
uptake is facilitated by
vitamin D
.
The body's calcium levels are controlled
by
parathyroid
hormone and
calcitonin.
Abnormally high levels in the blood
(
hypercalcaemia
) or abnormally low levels
(
hypocalcaem ia
) may seriously disrupt
cell function, particularly in muscles and
nerves. (See also
mineral supplements.
)
calcium channel blockers
Drugs used
to treat
angina pectoris
,
hypertension
, and
types of cardiac
arrhythmia.
Side effects
such as headaches, swollen ankles, flush-
ing, and dizziness may occur, but tend
to diminish with continued treatment.
calculus
A deposit on the teeth (see
calculus, dental
) or a small, hard, crys-
talline mass that is formed in a body
cavity from certain substances in fluids
such as bile, urine, or saliva. Calculi can
occur in the gallbladder and bile ducts
(see
gallstones
), the kidneys, ureters, or
bladder (see
calculus, urinary tract
), or in
the salivary ducts.
calculus, dental
A hard, crust-like de-
posit (also known as tartar) found on
the crowns and roots of the teeth. Cal-
culus forms when mineral salts in saliva
are deposited in existing
plaque
. Supra-
gingival calculus is a yellowish or white
deposit that forms above the gum mar-
gin, on the crowns of teeth near the
openings of
salivary gland
ducts. Sub-
gingival calculus forms below the gum
margin and is brown or black. Toxins in
calculus cause gum inflammation (see
gingivitis
), which may progress to de-
struction of the supporting tissues (see
periodontitis
). Calculus is removed by
professional
scaling. A
ttention to
oral
hygiene
reduces recurrence.
calculus, urinary tract
A stone in the
kidneys, ureters, or bladder formed from
substances in urine.
Most urinary tract stones are com-
posed of calcium oxalate or other salts
crystallized from the urine. These may
be associated with a diet rich in oxalic
acid (found in leafy vegetables and cof-
fee); high levels of
calcium
in the blood
as a result of
hyperparathyroidism
; or
chronic dehydration. Other types of stone
are associated with
gout
and some can-
cers. An infective stone is usually a result
of chronic
urinary tract infection
.
In developing countries, bladder stones
usually occur as a result of dietary defi-
ciencies. In developed countries, they
are usually caused by an obstruction to
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