MYOSIN
MYXOMA
Myopia, which tends to be inherited,
usually appears around puberty and
increases until the early 20s. If it starts
in early childhood it may become very
severe. The condition is detected during
a
vision test
.
Treatment is with concave
glasses
(or
contact lenses
)
or by
photo-
refractive keratectomy
.
myosin
A major protein component of
muscle
fibres. Together with
actin
, it
provides the mechanism for muscles to
contract. The myosin molecules slide
along the actin filaments to make the
muscle fibres shorter.
myositis
Inflammation of
muscle
tissue,
causing pain, tenderness, and weak-
ness. Types of myositis include
myositis
ossificans
(in which damaged muscle is
replaced by bone),
polymyositis
, and
dermatomyositis
.
myositis
ossificans
A
congenital
or
acquired condition in which bone is
deposited in muscles. The congenital
form is rare. The first symptoms are
painful swellings in the muscles, which
gradually harden and extend until the
affected child is encased in a rigid sheet.
There is no treatment, and death results.
The acquired form may develop after
a bony injury, especially around the
elbow; it causes severe pain and a
swelling, which hardens. Treatment with
diathermy
, coupled with gentle, active
movements, may be helpful.
myotomy
A surgical procedure that in-
volves cutting into a
muscle
.
myotonia
Inability of a
muscle
to relax
after the need for contraction has
passed. It is a feature of myotonic dys-
trophy, a form of
muscular dystrophy
.
myringitis
Inflammation of the ear-
drum. Myringitis occurs in
otitis media
.
myringoplasty
Surgical closure of a
perforation (hole) in the eardrum (see
eardrum, perforated
) by means of a tis-
sue graft (see
grafting
).
myringotomy
A surgical opening made
through the eardrum to allow drainage
of the middle-ear cavity. It is usually
performed to treat persistent
glue ear
in
children. A
grommet
may be inserted
into the eardrum at the same time.
myxoedema
A condition in which there
is thickening and coarsening of the skin
and other body tissues (most noticeably
in the face). Myxoedema is usually due
to
hypothyroidism
; in such cases, the
condition is commonly accompanied by
weight gain, hair loss, sensitivity to
cold, and mental dullness. The term
“myxoedema” is sometimes used for
adult hypothyroidism.
myxoma
A noncancerous, jelly-like tu-
mour composed of soft mucous material
and loose fibrous strands. Myxomas us-
ually occur singly, and may sometimes
grow very large. They may develop under
the skin, in the abdomen, in the bones,
or, very rarely, inside the cavities of the
heart. In this case, thrombi (blood
clots) may form, and the flow of blood
through the heart may be obstructed.
Myxomas can usually be successfully
removed by surgery.
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