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Muscles
and movement
Adrian
Whyte and Joanna Johnson, Contributor
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Members
of the Old Harbour High School's
Challenge Quiz team are quite
proud after beating Tacius Golding
25 - 11 yesterday. From left,
Odane McKoy, Mesha Hayden, Robert
Williams and Romario Levy (captain).
- Junior Dowie
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THERE
ARE three types of muscle, skeletal,
cardiac and smooth.
Cardiac
muscle is found only in the heart.
Smooth
muscle are our involuntary muscles
that are found in organs such as the
bladder, blood vessels and walls of
the alimentary canal.
Striated
muscles are voluntary muscles found
attached to bones.
STRUCTURE
IS RELATED TO FUNCTION
As
with most things in biology, 'form
follows function'. Bones are not different.
The
Long Bones (e.g. Femur)
(See
table below)
| CHARACTERISTIC
|
|
IMPORTANCE
|
| Hollow
in the centre (a tube) |
|
Increases
its tensile strength. The same
way the hollow tubular frame of
a bicycle is able to support a
grown man. |
|
Light
compared to its size
|
|
Easier
for animal to move about without
becoming too tired too quickly. |
|
Spongy
bone at head, compact bone at
perimeter
|
|
They
maintain the rigidity of bone
without being too heavy. |
|
Cartilage
at the ends
|
|
Reduces
friction at the articulating
surfaces. Serves as a cushion.
|
|
*
Tendons: Attaches muscle to
bone.
|
|
The
pull of the muscle is concentrated
over a very small area. |
| |
|
Helps
to prevent rupturing of muscle,
when muscle is subjected to a
heavy load suddenly |
|
**
Ligament: Attaches bone to bone
|
|
They
confine movement of the structures
at each joint to a specific direction. |
| |
|
They
strengthen joints.
|
| *
Tendons: Inelastic white fibrous
tissue which attaches muscle to
bone. |
|
(They
do not stretch) |
|
**
Ligament: Tough elastic white
fibrous tissue that attaches
bone to bone.
|
|
(They
can stretch slightly) |
MOVEMENT
IN HUMANS
Movement
is brought about by the contraction
of skeleton muscles (striated muscles)
across. Here, ligaments hold bones
together. They limit the movement
thus preventing dislocation. The joints
move due to the force of muscles acting
on them.
 Muscles
are attached to bones by tendons that
are made of collagen fibres. When
a muscle contracts, the tendon and
its attached bone are pulled towards
the contracting muscle.
Many joints work due to the action
of antagonistic muscles; one set causes
the joint to move one way, the other
set causes it to return. When one
muscle in the pair is contracting,
the other is relaxing (not stretching).
An example of this arrangement is
the elbow joint controlled by the
biceps and triceps muscle.
Ligaments
are made of connective tissue and
are elastic. Their function is to
hold bones together at a joint. Tendons
attach muscles to bones. They are
attached to the membrane called the
periosteum that covers the bone.
They
are composed of tough non-elastic
fibres. This prevents them from stretching
when the muscles contract.Wherever
two or more bones each other, a joint
is formed. There are two main kinds
of joints.
A
fibrous joint is one where the bones
are held firmly together by fibres.
These joints are called sutures. The
bones in the cranium of the skull
are joined like this. They are held
so firmly together in an adult human
that they cannot move at all. There
are also fibrous joints between the
vertebrae.
A
synovial joint or movable joint is
formed where two bones need to move
freely.
| JOINTS |
|
| Immovable
joints (Suture) e.g. skull, pelvic
girdle |
Moveable
joints |
|
Freely
moveable (synovial)
|
Slightly
moveable |
| |
e.g.
adjacent vertebrate |
| |
Sliding
joints (e.g. bones in hand) |
| Hinge
joints elbow
and hip |
Slightly
moveable e.g. adjacent vertebrate |
| Ball
and socket joints e.g. shoulder
and hip |
|
*
Adrian Whyte and Joanna Johnson
teach Biology at Ardenne High School
masterbio@gmail.com.
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