APHTHOUS ULCER
A
aphthous ulcer
See
ulcer, aphthous.
apical
A term used to describe the position of
structures that are found at the
apex
(tip) of particular organs and struc-
tures, including the lungs and heart.
apicectomy
The surgical removal of the tip of a
tooth root in order physically to elimi-
nate an infection or an infected cyst at
the root tip. The procedure was once
performed as part of
root-canal treatment
but is now used less often because root-
canal treatment alone usually achieves
the desired result.
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
insufficient
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 that can occur
either temporarily (for a few seconds or
up to a minute or two) or for a pro-
longed period.
CAUSES
Breathing is an automatic process that is
controlled by the respiratory centre in
the
brainstem
(a stalk of nerve tissue
linking the brain to the spinal cord).
The
respiratory
centre
sends
nerve
impulses that regulate contraction of
the diaphragm and muscles in the chest
wall, thereby controlling the rate and
depth of breathing. Failure of this centre
to maintain normal breathing is known
as central apnoea. The condition may
occur in babies, particularly those who
are premature, and can be detected by
an apnoea alarm. Central apnoea can
also be the result of damage to the
brainstem (following a
stroke
or
head
injury,
for example).
In obstructive apnoea, breathing is
prevented 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 respira-
tion,
in which cycles of deep, rapid
breathing alternate with episodes of
breathing stoppage.
TREATMENT
Treatment depends on the cause; in new-
born babies, apnoea resolves itself as
they mature. In cases of stroke or head
injury, artificial ventilation may be neces-
sary, temporarily, until recovery occurs.
apocrine gland
A gland that discharges cellular material
in addition to the fluid that it secretes.
The term apocrine is usually applied to
the type of
sweat glands
that appear in
hairy areas of the body after puberty.
(See also
eccrine gland.)
apocrinitis
Inflammation of the
apocrine glands
,
which are located in the armpit, groin,
and perineum.
apolipoprotein
Any of a group of proteins that are con-
stituents of
lipoproteins,
the carriers of
fat in the bloodstream. Apolipoproteins
are also involved in the growth and
repair of nerve tissues.
apomorphine
A drug that is used in the treatment of
Parkinson’s
disease. Nausea and vomit-
ing
are
common
side
effects
of
apomorphine at the start of treatment.
aponeurosis
A wide sheet of tough, fibrous tissue
that acts as a tendon by attaching a
muscle to a bone or a joint.
apophysis
An outgrowth of bone at the site of
attachment of a tendon to bone. Inflam-
mation
may
occur,
as
in
Osgood-
Schlatter disease.
apoplexy
An outdated term for a
stroke.
apoptosis
The natural process of programmed cell
death. Apoptosis occurs in embryonic
development,
when
the
shaping
of
body parts is taking place, and contin-
ues throughout life in the constant cycle
of death and renewal of body cells. Fail-
ure of apoptosis is implicated in the
development of cancers.
apothecary
An outdated term for a
pharmacist.
LAPAROSCOPIC APPENDICECTOMY
Surgery to remove the appendix can be
carried out, under general anaesthesia,
either conventionally or laparoscopically.
Laparoscopic appendicectomy takes
approximately an hour, which is three
times as long as conventional surgery,
but recovery is quicker.
Laparoscope
Power source
Instrument
Suction tube
Procedure
Three or four tiny
incisions are made
in the abdominal wall,
and a laparoscope,
instruments, and
suction tubes are
inserted. The appendix
isthen clamped, tied
off, and removed.
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