MISOPROSTOL
MITRAL INCOMPETENCE
The majority of miscarriages occur in
the first
12
weeks of pregnancy, and may
be mistaken for a late menstrual period.
Miscarriages may occur because of
chromosomal abnormalities
or develop-
mental defects in the fetus, or because
of severe illness, exposure to toxins, or
an
autoimmune disorder
in the mother.
Miscarriages later in pregnancy may be
caused by
genetic disorders
,
cervical
incompetence
, a defect in the uterus, or
large uterine
fibroids
.
The symptoms are heavy bleeding with
cramping. Slight blood loss with severe
pain can be a symptom of either a threat-
ened miscarriage or
ectopic pregnancy.
Miscarriages are classified medically
as different types of abortion. In a
threatened abortion, the fetus remains
alive in the uterus. In an inevitable
abortion, the fetus dies and is expelled
from the uterus. In a missed abortion,
the fetus dies but remains in the uterus.
A
pelvic examination
and
ultrasound
scanning
may be performed to assess
the pregnancy. If all of the contents of
the uterus are expelled, no further treat-
ment may be necessary. Otherwise, a
D
and C
may be performed. Missed abor-
tion requires a D and C or
induction of
labour
depending on the duration of the
pregnancy.
Rh-negative
women
are
given anti-D (Rho) immunoglobulin to
prevent complications related to
Rhesus
incompatibility
in future pregnancies.
(See also
abortion
.)
misoprostol
A synthetic
prostaglandin
drug
that inhibits gastric secretion. Miso-
prostol is used to prevent and treat
peptic ulcers
associated with use of
nonsteroidal anti-inflammatory drugs.
mites and disease
Mites are small ani-
mals, usually less than
1.2
mm, with
8
legs. Many species have piercing and
blood-sucking mouthparts.
Species causing disorders include the
scabies
mite, which burrows in human
skin causing intense itching; the house-
dust mite, which can cause
asthma
when inhaled in dust; and chiggers
(American harvest mites), which are
found in thick grass and cause an itchy
rash when they bite. Mites in grain or
fruit may cause skin irritation, some-
times known as grocers' or bakers' itch.
Certain mites transmit diseases, partic-
ularly scrub
typhus
and rickettsial
pox
.
mitochondria
Small
organelles
that are
found inside
cells
, in which cell
respira-
tion
takes place. The mitochondrial wall
consists of
2
membranes, and the inner
one is highly folded to provide a surface
for the respiration reactions. Cells that
use a lot of energy, such as muscle
cells, contain many mitochondria.
mitochondrial DNA
Mitochondria have
their own
DNA
. In human mitochondria,
the DNA is a double-helical circle that
codes for 13 proteins. Mitochondria
have a distinctive genetic code, and
their genomes are not changed by
meiosis
during reproduction,
making
the DNA useful in genetic studies.
The significance of mitochondria hav-
ing their own DNA is that diseases can
be inherited via abnormalities of mito-
chondrial DNA, and inheritance of the
DNA is maternal, directly from the egg.
mitosis
A type of cell division in which
the
chromosomes
within the nucleus of
a cell are exactly duplicated into each of
2
daughter cells.
Before cell division, the chromosomes
duplicate themselves and coil up with
the 2 copies joined together. The dou-
bled chromosomes line up in the centre
of the cell and are pulled apart to oppo-
site ends of the cell, which then divides.
Each daughter cell therefore has the
same chromosome content as the origi-
nal cell. (See also
meiosis
.)
mitral incompetence
Failure of the
mitral valve
of the
heart
to close properly,
allowing blood to leak back into the left
atrium (upper chamber) when pumped
out of the left ventricle (lower cham-
ber). The disorder, which is also known
as mitral regurgitation, may occur in
conjunction with
mitral stenosis
.
Symptoms include increasing breath-
lessness and fatigue, sometimes with
palpitations
. Later, the ankles may swell.
Diagnosis may be made by hearing a
characteristic heart
murmur
, and from
chest
X-rays
,
ECG
, and
echocardiography
.
Cardiac
catheterization
may also be per-
formed. Treatment may include
diuretic
drugs
,
vasodilator drugs
,
and
anticoagu-
lant drugs
.
If symptoms are disabling,
heart-valve surgery
may be considered.
372
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