APHTHOUS ULCER
APPENDIX
thought to stimulate erotic desire and
enhance sexual performance. For cent-
uries, various substances (most notably
oysters and rhinoceros horn) have been
used as aphrodisiacs. In fact, no sub-
stance has a proven aphrodisiac effect.
aphthous ulcer
See
ulcer, aphthous.
apicectomy
Surgical removal of the tip
of a tooth root. Apicectomy may be per-
formed as part of
root-canal treatment.
aplasia
Absent
or severely reduced
growth and development of any organ
or tissue. For example, in bone marrow
aplasia, the rate of cell division in the
bone marrow is reduced, leading to in-
sufficient blood-cell production (see
anaemia, aplastic).
Some birth defects,
such as stunted limbs (see
phocomelia),
occur as a result of incomplete tissue
formation during prenatal development.
aplastic anaemia
See
anaemia, aplastic.
apnoea
Cessation of breathing, either
temporarily or for a prolonged period.
Breathing is an automatic process
controlled by the respiratory centre in
the brainstem. Failure of this centre to
maintain normal breathing is known as
central apnoea. It may occur in babies,
particularly those who are premature,
and can be detected by an apnoea
alarm. Central apnoea can also result
from brainstem damage, for example
following a
stroke
or
head injury.
In obstructive apnoea, breathing is pre-
vented by a blockage in the airway. The
most common type is
sleep apnoea,
in
which blockage of the upper airway
occurs repeatedly during sleep.
Deliberate temporary apnoea occurs
in
breath-holding attacks.
Another type
of apnoea occurs in
Cheyne-Stokes res-
piration
, in which cycles of deep, rapid
breathing alternate with episodes of
breathing stoppage.
Treatment of apnoea depends on the
cause. In newborn babies, it resolves as
they mature. In stroke or head injury,
artificial ventilation may be needed
temporarily until recovery occurs.
apocrine
gland
A gland that dis-
charges cellular material in addition to
the fluid it secretes. The term is usually
applied to the type of
sweat glands
that
appear in hairy body areas after puberty.
(See also
eccrine gland.)
apolipoprotein
A group of proteins
that are constituents of
lipoproteins
, the
carriers of fat in the bloodstream. Apo-
lipoproteins are also involved in the
growth and repair of nerve tissues.
aponeurosis
A wide sheet of tough,
fibrous tissue that acts as a tendon,
attaching a muscle to a bone or a joint.
apophysis
An outgrowth of bone at the
site of attachment of a tendon to bone.
Inflammation may also occur, as in
Osgood-Schlatter disease.
apoplexy
An outdated term for a
stroke.
apoptosis
The natural process of pro-
grammed cell death. Apoptosis occurs
in embryonic development, when the
shaping of body parts is taking place
and continues throughout life in the
constant cycle of death and renewal of
body cells. Failure of apoptosis is impli-
cated in the development of cancers.
apothecary
An old term for a
pharmacist
.
appendicectomy
Surgical removal of the
appendix to treat acute
appendicitis.
appendicitis
Acute inflammation of the
appendix. The cause is usually not
known, but appendicitis is sometimes
caused by obstruction of the appendix
by a lump of faeces. The 1st symptom is
usually vague discomfort around the
navel. Within a few hours, this develops
into severe, more localized pain, which is
usually most intense in the lower right-
hand side of the abdomen. Symptoms
may differ if the appendix is not in the
most common position. For example, if
the appendix impinges on the ureter,
the urine may become bloodstained.
The usual treatment for appendicitis
is
appendicectomy
, which is often per-
formed endoscopically (see
minimally
invasive surgery).
If the treatment is
delayed, an inflamed appendix may
burst, releasing its contents into the
abdomen. This leads to
peritonitis
and,
in some cases, an
abscess
.
appendix
A small, narrow tube that
projects out of the caecum (the 1st part
of the colon) at the lower right-hand
side of the abdomen. It may lie behind
or below the caecum, or in front of or
behind the ileum (part of the small
intestine). The appendix has no known
function, but it contains a large amount
of lymphoid tissue which provides a
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