ACIDOSIS
ACOUSTIC NEUROMA
Disturbances of the body's acid-base
balance result in either
acidosis
(exces-
sive blood acidity) or
alkalosis
(excessive
blood alkalinity).
acidosis A disturbance of the body's
acid-base balance
in which there is an
accumulation of acid or loss of
alkali
(base). There are 2 types of acidosis:
metabolic and respiratory.
One form of metabolic acidosis is
ketoacidosis, which occurs in uncon-
trolled
diabetes melitus
and starvation.
Metabolic acidosis may also be caused
by loss of bicarbonate (an alkali) as a
result of severe diarrhoea. In
kidney fail-
ure,
there is insufficient excretion of
acid in the urine.
Respiratory acidosis occurs if breathing
fails to remove enough carbon dioxide
from the lungs. The excess carbon di-
oxide
remains
in
the
bloodstream,
where it dissolves to form carbonic acid.
Impaired breathing leading to respira-
tory acidosis may be due to chronic
obstructive pulmonary disease (see
pul-
monary disease, chronic obstructive),
bronchial
asthma,
or
airway obstruction.
acid reflu x Regurgitation of acidic fluid
from the stomach into the
oesophagus
due to inefficiency of the muscular valve
at the lower end of the oesophagus.
Also
known
as
gastro-oesophageal
reflux disease (GORD), acid reflux may
inflame the oesophagus, resulting in
heartburn
due to
oesophagitis.
It may
occur in pregnancy and often affects
overweight people.
acne A chronic skin disorder caused by
inflammation of the hair follicles and
sebaceous glands in the skin. The most
common type is acne vulgaris, which
almost always develops during puberty.
Acne spots are caused by the obstruc-
tion of hair follicles by sebum (the oily
substance secreted by the sebaceous
glands). Bacteria multiply in the follicle,
causing inflammation. The change in
sebum secretion at puberty seems to be
linked with increased levels of
androgen
horm ones
(male sex hormones).
Acne may be brought on or aggravated
by drugs such as
corticosteroids
and
androgens.
Exposure to certain chemi-
cals and oils in the workplace can also
cause a type of acne.
ACNE SPOT
Acne develops in areas of skin with a
high concentration of sebaceous glands,
mainly the face, centre of the chest,
upper back, shoulders, and around the
neck. Milia (whiteheads), comedones
(blackheads), nod-
ules (firm swel-
lings beneath the
skin), and cysts
(larger, fluid-filled
swellings) are the
most
commonly
occurring
spots.
Some, particularly
cysts, leave scars
after they heal.
There is no inst-
ant cure for acne,
but washing the
affected areas at
least twice daily
may help to keep
it under control.
Topical drug treat-
ments, such as benzoyl peroxide or
retinoic acid, unblock the pores and
promote healing. Ultraviolet light can
be beneficial. If topical treatment has
failed, oral drug treatment with
anti-
biotics
, hormones, or
isotretinoin
may be
given. Acne improves slowly over time,
often clearing up by the end of the
teenage years.
acoustic nerve The part of the
vestibu-
locochlear nerve
(the 8th
cranial nerve)
that is concerned with hearing. It is also
known as the auditory nerve.
acoustic neurom a A rare, noncancer-
ous tumour arising from supporting
cells that surround the 8th cranial nerve
(see
acoustic nerve
), usually within the
internal auditory meatus (the canal in
the skull through which the nerve pass-
es from the inner ear to the brain).
Usually, the cause of an acoustic neuro-
ma is unknown. However, tumours that
affect the nerves on both sides of the
head simultaneously may be part of a
condition known as
neurofibromatosis
.
Acoustic neuroma can cause
deafness
,
tinnitus
, loss of balance, and pain in the
face and the affected ear.
Diagnosis is made by
hearing tests
fol-
lowed by
X-rays, CT scanning,
or
MRI.
Surgery may be needed, but treatment
A
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