over the larynx to prevent food and
liquid from passing into the trachea
during swallowing.
la ry n x , c a n c e r o f
A cancerous tumour of the
l a r y n x
box). In more than half of the cases, the
tumour develops on one of the
v o c a l
c o r d s
; in the remainder, tumours arise
just above or below the cords.
The exact causes are not known, but
smoking and high alcohol consumption
are known risk factors.
H o a r s e n e s s
is the main symptom, par-
ticularly when the tumour originates on
v o c a l c o r d s .
At an advanced stage,
may include
difficulty in
breathing and swallowing, and cough-
ing up blood. The cancer may have
spread to the
l y m p h n o d e s
in the neck; if
so, the nodes w ill be enlarged.
l a r y n g o s c o p y
reveals a tumour on the
larynx, a
b i o p s y
(tissue sample) is taken.
If the tumour is small,
r a d i o t h e r a p y
l a s e r t r e a t m e n t
may be used to destroy it.
For unresponsive or large tumours, par-
tial or total
l a r y n g e c t o m y
(removal of the
larynx) may be considered.
la s e r
A device that produces an intense beam
of light. Lasers have many medical uses
l a s e r t r e a t m e n t ) .
la s e r tre a tm e n t
Use of a
l a s e r
beam in a variety of med-
ical procedures. Lasers can cut through
tissues, seal blood vessels, and destroy
abnormal cells. They can be focused
precisely so that tissues surrounding an
operation site are not damaged.
There are many different medical laser
systems, and they can be operated in a
variety of ways. Some emit light in brief
bursts and are known as pulsed lasers;
others emit a steady beam and are called
continuous wave lasers.
One of the most commonly used
devices is the carbon dioxide
laser, w hich can be operated in either
O f all
lasers, the CO2 laser has an action most
similar to that of a conventional scalpel.
It is used both for internal surgery,
including excision of brain tumours,
and for skin treatments, such as the
removal of noncancerous moles and
scarring, and the reduction of wrinkles.
The argon continuous laser emits a light
that is easily absorbed by the blood,
causing it to clot. This laser has applica-
tions in ophthalmology (particularly in
the treatment of abnormalities in the
r e t i n a
as a result of
d i a b e t e s m e l l i t u s ) ,
gery on the inner ear, and reduction of
birthmarks such as port-wine stains.
Another versatile laser is the yttrium-
treatments such as dentistry, hair and
tattoo removal, and lithotripsy (break-
ing up of kidney stones).Tattoo removal
and other dermatological treatments are
also often carried out with a system
known as the ruby laser, the light from
w hich is strongly absorbed by the pig-
ment melanin in hair and skin.
The abbreviation for laser-assisted in-situ
keratomileusis, a type of eye surgery in
w hich a
l a s e r
is used to reshape the
c o r n e a
(transparent front part of the eye).
LASIK is performed to correct refractive
errors (see
r e f r a c t i o n )
such as shortsight-
edness (see
m y o p i a )
a s t i g m a t i s m .
flap is cut partway through the cornea,
some of the area beneath is removed by
laser, and the flap is replaced.
L a s ix
A brand name for the diuretic drug
f u r o s e m i d e
L a s s a fe v e r
A serious infectious disease caused by a
rodent-borne virus. Lassa fever, w hich is
transmitted though contact with the
urine, faeces, or saliva of rodents, is
largely confined to West Africa. Symp-
toms appear after an incubation period
of three to 21 days with fever, head-
ache, muscular aches, and a sore throat.
Later, severe diarrhoea and vomiting
develop. In extreme cases, the condition
leads to fatal heart or kidney failure.
Treatment of Lassa fever is with the
antiviral drug
r i b a v i r i n ,
s e r u m
a n t i b o d i e s
to the virus.
L a s s a r’s p a ste
A traditional skin preparation that is
used in scaling conditions such as
p s o r -
i a s i s .
Lassar’s paste contains
s a l i c y l i c a c i d
z i n c o x i d e .
d i t h r a n o l
added to the paste.
la s s itu d e
A term describing a feeling of
t i r e d n e s s
weakness, or exhaustion.
The concentrated beam of light produced
by a laser has a variety of medical uses.
Among its applications are removal of skin
lesions, including birthmarks and tattoos,
surgery on the eye and inner ear, treatment
of tumours, and dentistry. Laser devices
operate at varying wavelengths and
energy levels for precise control;
some are used to treat specific
conditions only.
L a s e r -
P r o t e c t i v e g o g g l e s
Removing skin blemishes
These photographs, which were
taken before and after laser
treatment, show the removal
of a port-wine stain (a type of
haemangioma). In some cases,
treatment is less successful,
leaving scars.
Before treatment
After treatment
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