are soft and have an increased tendency
both to become deformed and to frac-
ture. The inherited disorder osteogenesis
imperfecta is a rare cause of brittle
bones and frequent fractures and is
usually detected in infancy.
Broca’s areaAn area of the cerebral
cortex (the outer layer of the brain) that
is responsible for speech origination.
broken toothSee fracture,dental.
broken veinsSee telangiectasia.
bromidesSubstances formerly used as
sedative drugs or as anticonvulsant
drugsin the treatment of epilepsy. They
are no longer prescribed because of
their side effects.
bromocriptineA drug used to suppress
production of the hormone prolactinto
treat conditions such as noncancerous
pituitary tumours (see prolactinomas
and acromegaly). Bromocriptine can be
used to suppress lactation after child-
birth. The drug may also be used as a
treatment for Parkinson’s disease. Side
effects of bromocriptine include nausea
and vomiting. High doses may cause
drowsiness and confusion.
bronchiectasisA lung disorder in which
1 or more bronchi (the air passages
leading from the trachea) are abnormally
widened, distorted, and have damaged
linings. Bronchiectasis most often deve-
lops during childhood and was once
commonly associated with infections
such as measlesand pertussis(whoop-
ing cough). The condition is also a
complication of cystic fibrosis. It results
in pockets of long-term infection within
the airways and the continuous produc-
tion of large volumes of green or yellow
sputum (phlegm). Extensive bronchi-
ectasis causes shortness of breath. The
symptoms are usually controlled with
antibiotic drugsand postural drainage. If
the condition is confined to one area of
the lung, surgical removal of the dam-
aged area may be recommended.
bronchioleOne of many small airways
of the lungs. Bronchioles branch from
larger airways (bronchi) and subdivide
into progressively smaller tubes before
reaching the alveoli (see alveolus,pul-
monary), where gases are exchanged.
bronchiolitisAn acute viral infection of
the lungs, mainly affecting babies andyoung children, in which the bronchi-
oles (the smaller airways branching off
from the bronchi in the lungs) become
inflamed. The most common cause is
the respiratory syncytial virus (RSV).
Symptoms include rapid breathing, a
cough, and fever. Sometimes no treat-
ment is necessary but, in more severe
cases, hospital admission is needed so
that oxygen therapyand physiotherapy
(to clear the mucus) can be given. With
prompt treatment, sufferers usually re-
cover within a few days. Antibiotic drugs
may be prescribed to prevent any sec-
ondary bacterial infection.
bronchitisA disorder in which the bron-
chi, the airways connecting the trachea
(windpipe) to the lungs, are inflamed.
Bronchitis results in a cough that may
produce considerable quantities of spu-
tum (phlegm) and may be acute or
chronic. Both types are more common
in smokers and in areas with high atmo-
spheric pollution. (See also bronchitis,
acute; bronchitis,chronic.)
bronchitis, acuteA form of bronchitis
that develops suddenly but usually clears
up within a few days. It is usually due to
a viral infection. Bacterial infection of
the airways may occur as a complica-
tion. Smokers, babies, elderly people,
and those with lung disease are particu-
larly susceptible. The main symptoms
are wheezing, shortness of breath, and
a cough that produces yellow or green
sputum. There may also be pain behind
the sternum (breastbone) and fever.
Symptoms may be relieved by drinking
plenty of fluids and inhaling steam or
using a humidifier. Most cases clear up
without further treatment, but acute
bronchitis may be serious in people
who already have lung damage.
bronchitis, chronicInflammation of
the airways, as a result of smoking, that
is always associated with emphysema.
The combination of chronic bronchitis
and emphysema are now known as chro-
nic obstructive pulmonary disease (see
pulmonary disease,chronic obstructive).
bronchoconstrictorA substance that
causes constriction (narrowing) of the
airways in the lungs. Bronchoconstric-
tors, such as histamine, are released
during an allergicreaction. They mayBROCA’S AREA BRONCHOCONSTRICTORB