LUNG CANCER
lu m b a r lo rd o s is
See
l o r d o s i s .
lu m b a r p u n c tu re
A procedure in which a hollow needle is
inserted into the lower part of the spinal
canal, between two lumbar
v e r t e b r a e ,
to
withdraw
c e r e b r o s p i n a l f l u i d
or to inject
drugs or other substances.
Lumbar puncture is usually carried
out to collect a sample of cerebrospinal
fluid in order to diagnose and investi-
gate disorders of the brain and spinal
cord (such as
m e n i n g i t i s
and
s u b a r a c h -
n o i d h a e m o r r h a g e ) .
The procedure takes
about
15
minutes and is carried out
under local
a n a e s t h e s i a
.
lu m b o s a c ra l s p a s m
Excessive tightening of the muscles that
surround and support the lower region
of the
s p i n e ,
causing
b a c k
pain.Treatment
of lumbosacral
spasm
may
include
a n a l g e s i c d r u g s
(painkillers) and
m u s c l e -
r e l a x a n t d r u g s .
lu m b o s a c ra l s p in e
The area of the lower
s p i n e
consisting of
the lumbar vertebrae and the
s a c r u m
(the fused vertebrae that form the back
of the pelvis).
lu m e n
The space w ithin a tubular organ or
structure such as the intestine.
lu m p e c to m y
A surgical treatment for
b r e a s t c a n c e r
in
w hich
only
the
cancerous
tissue
is
removed, rather than the entire breast.
(See also
m a s t e c t o m y ; q u a d r a n t e c t o m y . )
lu m p y ja w
A nonmedical name for
a c t i n o m y c o s i s .
lu n a c y
An outdated term for serious mental
disorder.
lu n g
One of the two main organs of the
r e s -
p i r a t o r y
s y s t e m .
The lungs supply the
body with the oxygen needed for
a e r o -
b i c
metabolism and eliminate the waste
product carbon dioxide.
STRUCTUREAND FUNCTION
Air is delivered to the lungs through
the
t r a c h e a
(windpipe); this air passage
divides into two main bronchi, with
one
b r o n c h u s
supplying each lung. The
main bronchi divide again into smaller
bronchi and then into bronchioles, which
lead to air passages that open out into
grapelike air sacs called alveoli (see
a l v e -
o l u s ,
p u l m o n a r y ) .
Oxygen and carbon
dioxide diffuse into or out of the blood
through the thin walls of the alveoli.
Each lung is enclosed in a double
membrane called the
p l e u r a ;
the two
layers of the pleura secrete a lubricating
fluid that enables the lungs to move
freely as they expand and contract dur-
ing breathing. (See also
r e s p i r a t i o n . )
lu n g c a n c e r
The second most common form of
c a n -
c e r
in the UK (after skin cancer).
CAUSES
S m o k i n g
of tobacco is the main cause
of lung cancer. Passive smoking (the
inhalation of tobacco smoke by non-
smokers) and environmental pollution
(with radioactive minerals or asbestos,
for example) are also risk factors.
TYPES
There are several types of lung cancer,
each of w hich affects a different group
of lung cells. The most common types
are squamous cell carcinoma and small
cell (or oat cell) carcinoma; the other
main types are adenocarcinoma and
large cell carcinoma.
Each form of lung cancer has a par-
ticular growth pattern and response to
L
DISORDERSOFTHE LUNG
The lungs are continuously exposed to
airborne particles, such as bacteria,
viruses, and allergens, all of which can
cause disease. Disorders may also arise
within the lung tissue or in associated
structures such as blood vessels.
Infection
Lung infections are common.These
include
p n e u m o n i a
(inflammation of the
lung),
t r a c h e i t i s
(inflammation of the
lining of the windpipe), and
c r o u p
(a
viral infection in young children).
B r o n c h i t i s
and
b r o n c h i o l i t i s ,
which are
inflammatory disorders affecting the
airways within the lungs, can be
complications of colds or
i n f l u e n z a .
The disorder
b r o n c h i e c t a s i s
(abnormal
widening of the bronchi) may be a
complication of bacterial pneumonia
or
c y s t i c f i b r o s i s .
Allergies
Inhalation of certain substances, such
as pollen,
d a n d e r
(skin cells from
animals), and house mite faeces, can
provoke allergic disorders in susceptible
people. The most significant of these
disorders is
a s t h m a
.Another such disorder
is allergic
a l v e o l i t i s ,
which is usually a
reaction to dust of plant or animal origin.
Tumours
L u n g c a n c e r
is one of the most common
of all cancers; cancerous tumours may
also spread to the lungs from other areas.
Noncancerous tumours of the lung are
far less common.
Injury
Injury to the lung, usually by penetration
of the chest wall, can allow air or blood to
collect between the two layers of the
pleura (the membrane around each lung),
and the lung may collapse (see
p n e u m o -
t h o r a x ; h a e m o t h o r a x
). Injury to the interior
of the lungs can be due to inhalation of
toxic substances (see
a s b e s t o s i s ; s i l i c o s i s
).
Other disorders
The blood supply to the lungs may be
reduced by
p u l m o n a r y e m b o l i s m
(a
condition in which a clot obstructs a
blood vessel in the lung).
Oxygen intake may be severely
impaired by diseases affecting the tiny
air sacs in the lungs (see
a l v e o l u s ,
p u l m o n a r y ) .
In
e m p h y s e m a ,
the alveoli
are destroyed, thereby reducing the
area of lung tissue where oxygen is
absorbed into the blood (see also
p u l m o n a r y d i s e a s e , c h r o n i c o b s t r u c t i v e ) .
R e s p i r a t o r y d i s t r e s s s y n d r o m e
in adults
occurs when fluid leaks into the
alveoli from the tiny blood vessels
surrounding them, thereby preventing
the alveolar walls from absorbing
sufficient oxygen.
INVESTIGATION
Lung disorders are investigated by
ch estX- ray, CT scanning, bronch os copy,
pulmonaryfunction tests, sputum
analysis,
and
blood tests.
Sometimes,
a lung
biopsy
(removal of a tissue
sample) is performed.
477
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