LABETALOL
LACTIC ACID
labetalol
A
beta-blocker drug
that is
used to treat
hypertension
and
angina
pectoris
.
Possible adverse effects include
indigestion, nausea, and, in rare cases,
depression
and temporary
impotence
.
labia
The folds of skin of the
vulva
that
protect the vaginal and urethral open-
ings. There are 2 pairs of labia. The
outer pair, the labia majora, are fleshy
folds that bear hair and contain sweat
glands. They cover the smaller, hairless
inner folds, the labia minora, which
meet to form the hood of the
clitoris
.
labile
A term meaning unstable or likely
to undergo change.
labour
See
childbirth
.
labyrinth
The collective term for the
convoluted structures of the inner
ear
.
The first part of the labyrinth is the
coch-
lea
, which contains the mechanism of
hearing
. Situated behind the cochlea
are
2
sacs (the saccule and the utricle)
and 3 fluid-filled semicircular canals, all
of which are concerned with
balance
.
labyrinthitis
Inflammation of the
laby-
rinth
. The condition is almost always
caused by bacterial or viral infection.
Viral labyrinthitis may develop during
illnesses such as influenza. Bacterial
labyrinthitis is commonly a complica-
tion of
otitis media
. The main symptom
is
vertigo
,
sometimes with
nausea,
vomiting,
nystagmus
,
tinnitus
, and hear-
ing loss. Viral labyrinthitis clears up on
its own, but symptoms are relieved by
antihistamine drugs
.
Immediate treat-
ment with
antibiotic drugs
is needed for
bacterial labyrinthitis, otherwise perma-
nent
deafness
or
meningitis
may result.
laceration
A torn, irregular
wound
.
lacrimal apparatus
The system that
produces and drains
tears
.
The lacrimal
apparatus of the eye includes the main
and accessory lacrimal glands and the
nasolacrimal drainage duct. The main
gland lies just within the upper and outer
LACRIMAL APPARATUS
margin of the eye orbit and drains on to
the
conjunctiva
.
It secretes tears during
crying and when the eye is irritated. The
accessory gland lies within the conjunc-
tiva, and maintains the normal tear film,
secreting it directly onto the conjunctiva.
Tears drain through the lacrimal puncta,
tiny openings towards the inner ends of
the upper and lower eyelids. The puncta
are connected by narrow tubes to the lac-
rimal sac, which lies within the lacrimal
bone on the side of the nose. Leading
from the sac is the nasolacrimal duct,
which opens inside the nose.
lactase deficiency
A condition in which
there is an absence of lactase, an
en-
zyme
that breaks down
lactose
(milk
sugar), in the cells of the small intes-
tine. Lactase deficiency results in a
reduced ability to digest lactose, also
known as
lactose intolerance
.
The condi-
tion may be permanent, or may occur
temporarily after gastroenteritis, par-
ticularly in young children. Symptoms
include abdominal cramps, bloating,
flatulence
, and
diarrhoea
, all of which
are caused by the laxative effect of the
undigested sugar in
the intestines.
Treatment is with a lactose-free diet.
lactation
The production and secretion
of breast milk (see
breast-feeding
).
lactic acid
A weak acid that is produced
when body cells break down
glucose
by
anaerobic
metabolism in order to pro-
duce energy. Lactic acid is produced by
muscles during vigorous exercise and is
one of the factors that contribute to
cramp
. The acid is also produced in
body tissues when they receive insuffi-
cient oxygen due to impairment of their
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