Download Movement of the skeleton - E

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How does the bony skeleton move?
The skeleton is able to move because of muscles and joints. Bones are connected to
other bones by joints. Joints are where two or more bones meet. Bones at joints act as
levers during movement.
There are three types of joints classified by the amount of movement they allow:
immovable, slightly movable, and freely movable. Most of the joints in the adult body
are freely movable joints. This type of joint is called a ‘synovial’ joint. There are six types
of synovial joints. These are:
• Pivot joint – these joints allow rotation around an axis, such as the axis and atlas in
the neck.
• Hinge joint – these joints allow varied degrees of movement in one plane only, such
as the elbow and knee.
• Ball-and-socket joint – the ball-shaped end of one bone fits into a cup shaped
socket on the other bone allowing a wide range of movement and rotation, such as
the shoulder and hip.
• Gliding or plane joint – these joints are flat surfaces which move against each other
in a sliding motion without any circular movement, such as tarsals in ankles and
carpals in wrists.
• Condyloid joint – Oval shaped condyle fits into elliptical cavity of another allowing
angular motion, but not rotation. This occurs between the metacarpals (bones in the
palm of the hand) and phalanges (fingers) and between the metatarsals (foot bones
excluding heel) and phalanges (toes).
• Saddle – these joints occur when the touching surfaces of two bones have both
concave and convex regions with the shapes of the two bones complementing one
other and allowing a wide range of movement. The only saddle joint in the body is
in the thumb.
GRADE 5
Grade 5 Term 1 Natural Sciences Life and Living; Animal Skeletons
Movement of the skeleton
Structure of a moveable joint
ligament
cartilage
synovial membrane
• The ligament in a joint prevents dislocation and allows the limb bones
at the joint to move in a controlled way.
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Types of movements at synovial joints:
• Flexion: A movement decreasing the angle between articulating bones.
• Extension: A movement increasing the angle between articulating bones.
• Hyperextension: A movement which increases the angle between articulating bones to
take a body-part or limb beyond its normal range.
• Abduction: A movement away from the midline of the body.
• Adduction: A movement toward the midline of the body.
• Circumduction: A movement in a circular motion allowing 360 degree movement.
Activity 1 – Label the 6 synovial joints:
Muscles and the skeleton
Muscles are the body’s principal effectors for movement.
Muscles contract when they are stimulated, which in turn,
allows movement of the bones. Muscles are attached to bones
through tendons. When muscles are relaxed and contracted, this
produces the movement of the limb bones.
Activity 2:
Study the forearm showing the biceps and the triceps when
bending an arm.
Label which muscle is the flexor and which muscle is the
extensor.
GRADE 5
Grade 5 Term 1 Natural Sciences Life and Living; Animal Skeletons
• The synovial membrane secretes synovial fluid to reduce friction between the bones.
• The cartilage acts as a shock absorber, provides protection against wear and reduces
friction between the bones.
A flexor is a muscle
which bends a limb
when it contracts.
An extensor is
a muscle which
straightens the
same limb when it
contracts.
©e-classroom 2014www.e-classroom.co.za
Activity 1 – Label the 6 synovial joints:
plane/gliding joint
hinge joint
saddle joint (in thumb)
ball-and-socket
pivot joint
Activity 2:
Study the forearm showing the biceps and the triceps in movement.
Label which muscle is the flexor and which muscle is the extensor.
tricep (extensor)
condyloid joint
Grade 5 Term 1 Natural Sciences Life and Living; Animal Skeletons
GRADE 5
Answer sheet
bicep (flexor)
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