Biology Revision: Skeleton and Muscles
The skeleton has three main functions:
• To support the body (keep you upright)
• To protect vital organs e.g. ribcage protects lungs and heart; skull
protects the brain)
• To allow movement (e.g. joints)
Facts
• There are over 200 bones in the human body.
• The mineral calcium makes the bones very hard.
• In the centre of the bone there is bone marrow – a substance that
makes red blood cells.
Note
• Ligaments: attach bones to bones.
• Tendons: attach muscles to bones.
Types of joints
• Hinge joint – found at the elbow and knee
• Ball and socket joint – found at the shoulder and hip.
Diagram of a Knee joint
Note: Cartilege allows the bones to move smoothly. If the cartilege
wears out it can lead to osteoarthritis.
Ligament Muscles
• Muscles are made of protein.
Antagonistic pairs of muscles
• Muscles can only contract (shorten) and relax (lengthen).
• Muscles work in pairs in order to move bones (e.g. bicep and tricep
in the upper arm).
Example: Upper arm movement
To pull the arm up
• The bicep contracts and the tricep relaxes
To pull the arm down
• The bicep relaxes and the tricep contracts