Medical Terminology and Cancer
© Copyright 1996-2000
7: The Muscular System
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The main function of muscles is for motion, for example in
conjunction with bones for walking. Muscles may work alone e.g.
the diaphragm for breathing, and the heart for circulating
blood.
- Irritability (excitability) muscles receive and respond to stimulation.
- Contractability allows muscles to change shape to become shorter and thicker.
- Extendibility living muscle cells can be stretched and extended; longer and thinner.
- Elasticity once the stretching force is removed a living muscle cell retains it's original shape.
Different types of muscle respond, contract, and relax at
different rates.
Skeletal muscles are striated (have distinct
bands) made up of fibres (long cells). The cells are
multinucleated (many cell nuclei) and contract and relax
quickly. These are voluntary muscles attached to the
skeleton that help to move the bones. There are nearly 700
skeletal muscles spread all over the body.
Visceral muscles are smooth and without banding. They
have short fibres and single cell nuclei. These are involuntary
muscles e.g. found in walls of blood vessels and viscera (organs
in the abdominal cavity).
Cardiac muscles are striated (but less
distinct than skeletal muscles), and are involuntary .
The diaphram is the major muscle for breathing
(respiration). The diaphragm is located in the rib cage below
the lungs. It is a dome shaped muscle that pulls / pushes air in
and out of the lungs. 'Hiccups' are a spasm of the diaphragm.
Intercostals also aid respiration Inter- (between)
Costals (ribs). Internal intercostals lift the ribs
during respiration, whilst external intercostals draw the
ribs together during expiration to lessen the volume of the rib
cage and thoracic cavity to push air out of the lungs.
Biceps and triceps are antagonist
(have the opposite functions). Triceps (with three 'heads')
extend the forearm so it can be held straight, while biceps (two
'heads') flex the forearm and draw it up.
Tendons connect muscles to the bone, these are formed
from the connective tissue that cover the muscle. They are dense
white cords of tissue which are strong and flexible, they serve
to anchor muscles to the bone.
Types of muscles and movement
Most movements involve several skeletal muscles working
together. Most skeletal muscles are arranged in opposing pairs
at joints, for example one muscle tightens up while the other
extends.
Flexors tighten to decrease the angle of a joint
Extensors relax to increase the angle of a joint
Abductors move a bone away from the midline
Adductors move a bone toward the midline
Levators make an upward movement
Depressors make a downward movement
Supinators turn the palm upwards or inwards
Pronators turn the palm downwards or outwards
Sphincters decrease the size of an opening
Tensors makes part of the body more rigid
Rotators moves a bone around
| component | meaning | example
|
| SARC- | tissue | sarcoma = tumour of supportive tissues (muscle, bone etc.)
|
| INTRA- | into | intramuscular injection = injection into a muscle
|
| MYO- | muscle | myocardium = heart muscle
|
| BI- | two | biceps = muscles with two heads
|
| TRI- | three | triceps = muscles with three heads
|
- Rhabdomyosarcoma
-
Rhabdomyosarcoma is a malignant tumour of striated muscle
found in children and young adults.
Rhabdomyosarcoma accounts for about two thirds of childhood soft
tissue sarcomas. There are 3 broad histological sub-types:
- Embryonal rhabdomyosarcoma occurs maily in infants
and young children, usually arising in the head, neck or
genitourinary system (especially the testis, prostate, vagina,
and bladder).
- Alveolar rhabdomyosarcoma is most common in
adolescents and young adults, mostly found in peripheral muscles.
- Pleomorphic rhabdomyosarcoma is most common in
adults, usually found in the muscles of the extremities in
adults.
Internet Resources for Rhabdomyosarcoma
- Other types of Soft Tissue Sarcoma
-
Other types of cancer affecting muscles and soft tissues in children include:
fibrosarcoma (begins in fibrous tissue in the arms and legs)
neurofibrosarcoma (begins in nerves near the surface of arms, legs, and trunk)
leiomyosarcoma (muscles in the trunk)
liposarcoma (begins in fat in the arms and legs)
synovial sarcoma (begins in linings of joint
cavities and tendon sheaths)
hemangiopericytoma (begins in blood vessels in the
arms, legs, trunk, head,and neck).
alveolar soft part sarcoma (begins in nerves of the
muscles in the arms and legs)
malignant fibrous histiocytoma (begins in fibrous
tissue).
Internet Resources for Soft Tissue Sarcoma
- Potential Side Effects of Radiotherapy on Muscles
-
Muscles can be damaged by radiotherapy which can cause fibrosis,
muscle shortening and atrophy. Any potential side effects will
depend on the site of the tumour, the patients age, and the dose
of radiotherapy. For example high dose radiotherapy in may
result in footdrop which is a condition where the
anterior muscles of the leg are paralysed. Second
malignancies particularly fibrosarcomas can also develop in
previously irradiated sites.
Related Abbreviations and Acronyms:
ARMS | Alveolar rhabdomyosarcoma
|
IM | Intramuscular - into a muscle
|
MPNST | Malignant Peripheral Nerve Sheath Tumour
|
NRSTS | Non-Rhabdomyosarcoma Soft Tissue Sarcoma
|
RMS | Rhabdomyosarcoma
|
More Cancer Related Abbreviations
This guide by Simon Cotterill
Department of Child Health
University of Newcastle upon Tyne
UK
First created 04/03/96
Last modified: 31/08/2000