SIEVERT
SINUS, FACIAL
sievert A unit for measuring doses of
ionizing
radiation.
(See
radiation units).
sight See
vision.
sight, partial Loss of vision short of
total
blindness.
Partial sight may involve
loss of
visual acuity
and/or
visual field.
sigmoid colon The S-shaped part of
the
colon,
in the lower abdomen, extend-
ing from the brim of the pelvis, usually
down to the 3rd segment of the
sacrum.
It is connected to the descending colon
above, and the rectum below,
sigmoidoscopy A form of
endoscopy
in
which a viewing instrument is inserted
through the anus to examine the
rectum
and
sigmoid colon.
sign An objective indication of a dis-
ease or disorder (for example, jaundice)
that is observed or detected by a doctor,
as opposed to a
s^miptom
(for example,
pain), which is noticed by the patient,
sildenafil Commonly known by its brand
name Viagra, a drug used in the treat-
ment of
impotence.
Because of the risk
of potentially serious side effects in cer-
tain people, the drug must only be used
on medical advice.
silicone A long-chain, carbon-containing
compound of silicon and oxygen. Synth-
etic silicones are sometimes used as
implants in
cosmetic surgery.
silicosis A lung disease caused by the
inhalation of dusts containing silica.
(See also
pneumoconiosis.)
silver
sulfadiazine An
antibacterial
drug
applied as a cream to prevent infec-
tion after skin grafts or in burns, leg
ulcers, and pressure sores. Side effects
may include permanent grey skin dis-
coloration, rashes, or itching,
simvastatin A
lipid-lowering drug
that
acts on the liver enzymes that produce
cholesterol.
It may cause bowel upsets,
headaches, and muscle pains,
sinew A nonmedical term for a
tendon.
singer's
nodes Small, greyish-white
nodules that develop on the vocal cords
as the result of constant voice strain. In
acute cases, treatment consists of rest-
ing the voice. In chronic cases, surgical
removal of the nodes may be necessary,
sinoatrial node The natural pacemaker
of the
heart.
The sinoatrial node consists
of a cluster of specialized muscle cells
in the right atrial wall. These cells regu-
larly emit electrical impulses, which
initiate the contractions of the heart,
sinus A cavity in a bone, in particular
one of the air-filled spaces in the bones
surrounding the nose (see
sinus
,
facial).
The term sinus also refers to any wide
channel that contains blood, or to an
abnormal, often infected, tract,
sinus bradycardia A slow, but regular
heart-rate (less than 60 beats per min-
ute) caused by reduced electrical activity
in the
sinoatrial node.
Sinus bradycardia
is normal in athletes, but in others it may
be caused by
fyspottysroidism,
a
myo-
cardial infarction,
or by drugs such as
beta-blockers
or
digoxin.
sinus, facial Any of the air-filled cavi-
ties in the bones surrounding the nose.
These include 2 frontal sinuses in the
SINUS, FACIAL
510
previous page 508 BMA Illustrated Medical Dictionary read online next page 510 BMA Illustrated Medical Dictionary read online Home Toggle text on/off