LIMB DEFECTS
lim b d e fe c ts
The
incomplete
development of one
or
more
limbs at birth. Limb
defects are
rare
and
may
be
inherited
or form
part
of a
s y n d r o m e
.
In a
condition
called
p h o c o m e l i a
,
hands, feet, or tiny finger- or toe-buds
are
attached
to
limb
stumps or grow
directly from
the
trunk. The
sedative
drug
t h a l i d o m i d e
,
when
taken
by
preg-
nant women, is known
to
have
caused
phocomelia
in fetuses.
lim b ic s y ste m
A
ring-shaped
area
in the
centre
of the
b r a i n
consisting
of a
number of con-
nected
clusters of nerve
cells. The
limbic
system
plays a
role in influencing
the
a u t o n o m i c n e r v o u s s y s t e m
,
which
auto-
matically
regulates body
functions; the
emotions; and
the
sense
of smell. The
system
is extensive, and
contains vari-
ous different substructures including
the
h i p p o c a m p u s
,
the
cingulate
gyrus,
and
the
amygdala.
lim b , p h a n to m
L
See
p h a n t o m l i m b
.
lim ite d c u ta n e o u s s y s te m ic
s c le r o s is
See
s y s t e m i c s c l e r o s i s
.
lim p
An
abnormal pattern
of
w a l k i n g
in
which
the
movements of one
leg
(or of
the
h i p
on
one
side
of the
body) are
dif-
ferent from
those
of the
other. If a
child
is limping, a
doctor should
be
con-
sulted
w
ithin
24
hours, because
the
problem
may
result from
a
hip
disorder
that requires prompt treatment.
lin c t u s
A
bland, usually sweetened
m
ixture
taken
to
soothe
irritation
caused
by
an
inflamed
t h r o a t
.
A
simple
linctus con-
tains no
active
drug, but linctuses are
commonly
used
as a
basis for cough
suppressants (see
c o u g h r e m e d i e s
).
lin d a n e
A
drug
formerly used
to
treat infesta-
tion
by
s c a b i e s
and
some
types of
l i c e
.
Lindane
has now
been
replaced
by
other, less toxic drugs.
lin e a a lb a
A
vertical line of fibrous tissue
running
down
the
m
iddle of the
abdom
inal
wall. The
linea alba
is the
site
of attach-
ment of the
rectus abdom
inis
m u s c l e s
and
extends from
the
xiphoid
process
(the lowest part of the
breastbone) to
the
pubic symphysis (the joint between
the
two
pubic bones). The
skin
over the
linea alba
becomes pigmented
during
pregnancy
(see
l i n e a n i g r a
).
lin e a n ig ra
A
pigmented, vertical line that appears
down
the
front of the
abdomen
during
p r e g n a n c y
.
The
linea nigra is a
visible
form
of the
l i n e a a l b a
and
often
fades
again
after childbirth.
lin e a r a c c e le ra to r
A
device
for accelerating
subatom
ic par-
ticles, such
as electrons, to
a
speed
approaching
that of light so
that they
have
extremely
high
energies. A
linear
accelerator can
also
be
used
to
generate
high-energy
X - r a y s
.
H
igh-energy elec-
trons or X-rays are
used
in
r a d i o t h e r a p y
to
treat certain
cancers.
lin g u a l
A
term
meaning
“of the
tongue”, as in
“sublingual
drug”
(a
drug
that is
adm
inistered
under the
tongue).
lin im e n t
A
liquid that is rubbed
on
the
skin
to
relieve
aching
muscles and
stiff joints.
Liniments
may
contain
rubefacients
(substances that increase
blood
flow
be-
neath
the
skin), or certain
drugs, such
as
n o n s t e r o i d a l a n t i - i n f l a m m a t o r y d r u g s
.
lin k a g e a n a ly s is
A
type
of
g e n e m a p p i n g
.
Linkage
analysis
determ
ines the
presence
or absence
of
an
abnormal gene
by
detecting
another
gene
located
close
to
it on
the
same
c h r o m o s o m e
.
lin k a g e , s e x
The
association
of a
particular
g e n e t i c
d i s o r d e r
w
ith
the
sex
chromosomes (see
s e x - l i n k e d i n h e r i t a n c e
).
lin o le ic a c id
An
essential
f a t t y a c i d
found
principally in
plant seed
oils, such
as maize
oil and
soya
bean
oil. Linoleic acid
is used
by
the
body
in the
synthesis of
p r o s t a g l a n d i n s
and
cell
membranes. Linoleic acid
has to
be
obtained
from
the
diet because
the
body
cannot manufacture
its own
supplies.
lin o le n ic a c id
An
essential
f a t t y a c i d
,
found
in fish
oils
and
some
plant seed
oils, that is used
by
the
body
to
form
p r o s t a g l a n d i n s
;
linol-
enic acid
can
be
synthesized
by
the
body
from
l i n o l e i c a c i d
obtained
in the
d
iet.
lin t
A
soft, absorbent fabric used
in surgical
dressings.
lio th y ro n in e
A
t h y r o i d h o r m o n e
used
as replacement
therapy
in
h y p o t h y r o i d i s m
(underactivity
of the
thyroid
gland). Liothyronine acts
faster than
l e v o t h y r o x i n e
and
is cleared
from
the
body
more
rapidly.
lip
One
of two
fleshy
folds around
the
entrance
to
the
mouth. The
main
sub-
structure
of the
lips is a
ring
of muscle
that helps to
produce
speech. Smaller
muscles at the
corners of the
lips are
responsible
for facial expression.
D
isorders of the
lips include
c h a p p e d
s k i n
,
c h e i l i t i s
(inflammation, cracking,
and
dryness),
c o l d s o r e s
,
and
l i p c a n c e r
.
lip a e m ia
An
abnormally
high
level of fat in the
blood. (See
also
h y p e r l i p i d a e m i a s .
)
lip c a n c e r
A
m a l i g n a n t
tumour (usually a
s q u a m o u s
c e l l c a r c i n o m a
) ,
commonly
on
the
lower
l i p
.
Lip
cancer is largely
confined
to
older people, particularly those
who
have
been
exposed
to
a
lot of sunlight
and
those
who
have
smoked
cigarettes
or a
pipe for many
years.
The
first symptom
is a
white
patch
that develops on
the
lip and
soon
becomes scaly
and
cracked
w
ith
a
yel-
low
crust. The
affected
area
grows and
eventually
becomes ulcerated. In some
cases, the
cancer spreads to
the
l y m p h
n o d e s
in the
jaw
and
neck.
Lip
cancer is diagnosed
by
b i o p s y
(taking
a
sample
of the
lip
tissue
for
m
icroscopic exam
ination). Treatment is
surgical removal,
r a d i o t h e r a p y
,
or a
com
-
bination
of both.
lip e c to m y , s u c tio n
A
type
of
b o d y
c o n t o u r s u r g e r y
,
com
-
monly known
as liposuction, in which
excess fat is sucked
out through
small
skin
incisions, using
a
cannula
(thin
tube) attached
to
a
vacuum
device.
lip id d is o rd e rs
M
e t a b o l i c d i s o r d e r s
that result in abnor-
mal amounts of
l i p i d s
(fats) in the
body.
The
most common
lipid disorders are
the
h y p e r l i p i d a e m i a s
,
which
are
charac-
468
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