Bma Illustrated Medical Dictionary

other substances. Lumbar puncture is
usually carried out to collect a sample
of cerebrospinal fluid in order to diag-
nose and investigate disorders of the
brain and spinal cord (such as meningi-
tisand subarachnoid haemorrhage). The
procedure takes about 15 minutes and
is carried out under local anaesthesia.
lumbosacral spasmExcessive tight-
ening of the muscles that surround and
support the lower region of the spine,
causing back pain. Treatment of lumbo-
sacral spasm may include analgesic drugs
and muscle-relaxant drugs.
lumenThe space within a tubular organ,
such as the intestine.
lumpectomyA surgical treatment for
breast cancer in which only the cancerous
tissue is removed. (See also mastec-
tomy;quadrantectomy.)
lunacyAn outdated term for serious
mental disorder.
lungOne of the 2 main organs of the
respiratory system. The lungs supply the
body with the oxygen needed for aero-
bicmetabolism and eliminate the waste
product carbon dioxide. Air is delivered
to the lungs via the trachea(windpipe);
this branches into 2 main bronchi (air
passages), with 1 bronchussupplying
each lung. The main bronchi divide again
intosmaller bronchi and then into bron-
chioles, whichlead to air passages that
open out into grape-like air sacs called
alveoli (see alveolus, pulmonary). Oxy-
gen 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 pleura; the

two layers of the pleura secrete a lubri-

cating fluid that enables the lungs to

move freely as they expand and contract

during breathing. (See also respiration.)

lung cancerThe most common form of

cancerin the UK. Tobacco-smokingis

the main cause. Passive smoking (the

inhalation of tobacco smoke by non-

smokers) and environmental pollution

(for example, with radioactive minerals

or asbestos) are also risk factors.

The first and most common symptom is

a cough. Other symptoms include cough-

ing up blood, shortness of breath, and

chest pain. Lung cancer can spread to

other parts of the body, especially the

liver, brain, and bones. In most cases,

the cancer is revealed in a chest X-ray.

To confirm the diagnosis, tissue must be

examined microscopically for the pres-

ence of cancerous cells (see cytology). If

lung cancer is diagnosed at an early

stage, pneumonectomy(removal of the

lung) or lobectomy(removal of part of

the lung) may be possible. Anticancer

drugsand radiotherapymay also be used.

lung, collapse ofSee atelectasis; pneu-

mothorax.

lung disease, chronic obstructiveSee

pulmonary disease, chronic obstructive.

lung, disorders ofThe most common

lungdisorders are infections. These dis-

eases include pneumonia,tracheitis, and

croup. Bronchitis and bronchiolitis, which

are inflammatory disorders affecting the

airways within the lungs, can be compli-

cations of colds or influenza. The disorder

bronchiectasismay occur as a complica-

tion of severe bacterial pneumonia or

LUMBOSACRAL SPASM LUNG, DISORDERS OF

L

Pleura

Lobe Bronchus

Trachea

LOCATION

LUNG

ALVEOLI

Bronchiole

Air space

Blood

vessel

Thin wall

of alveolus

Left lung

Right lung