Muscles and the skeleton

Muscles and the skeleton

1. Bones

   • The human skeleton is made up of 206 bones.
   • Most bones are hollow and contain marrow.
     • Marrow helps bones to be light and strong
   • Bones are a mixture of living tissue and non-living material
     • Living tissues contain cells and collagen fibres which allow bones to be flexible
     • The non-living part is made of mineral salts like calcium phosphate which hardens the bone.

2. Functions of the skeleton

   • Support
     • 1. They provide support allowing the body to stand upright
   • Protection
     • 2. They protect most of the main organs including the brain heart and lungs
   • Movement
     • 3. They allow movement with the help of muscles
   • Blood production
     • 4. Blood is produced in the marrow of bones

3. Joints

   • A place where two bones meet is called a joint. There are three types of joints:
     • 1. Fixed joints- where there is no movement although bones meet
     • 2. Hinge joints- where bones move only in One Direction
     • 3. Ball and socket joints- where bones can swivel and move in any direction
     • Parts of a joint
       • Cartilage: A tough smooth substance that covers bone surfaces at movable joints.
       • Ligaments: A smooth, flexible material that holds bones together at movable joints
       • Tendons: Attach muscles to bone and transmits the pull of muscle to bone
       • Synovial fluid: lubricates the joint and reduces friction

4. Muscles

   • Muscles move bones at joints
   • Muscles cannot push and so joints need pairs of muscles (antagonistic pairs) to pull in the opposite direction
     • One muscle contracts (gets shorter and fatter) to pull a bone.
       • At the same time
         • The other muscle in the pair relaxes (gets longer and thinner
   • Exercise strengthens bones and muscles. Too much exercise can damage muscles and joints.

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