musculoskeletal system

• the adult skeleton is made of 206 bones
• your skeleton is your body's frame and is made up of bones
• three main functions of your skeleton:

  • support for your soft tissue
  • protection for organs (main role of axial skeleton > made up of 80 bones: includes skull, ribs and breastbone)
  • to allow movement (main role of appendicular skeleton > made up of 126 bones: includes shoulder blades and bones in arms + legs)
• the axial and appendicular skeleton

  
• bones need to be

  • strong (so they don't snap/crumble during normal activity)
  • slightly elastic (to flex and twist a little but still return to their original shape)
  • light (so your muscles can move)
• bone tissue has two forms:

  • compact bone (makes outer layer of bone)
  • spongy bone (resembles honeycomb)
• compact bone is dense and heavy, giving bone most of its strength
• spongy bone is light but provides a strong inner structure to bone. gaps in spongy bone are filled with a fatty, jelly like material called bone marrow (where red blood cells, platelets and some white blood cells are made)
• bones are living tissues, therefore are able to repair themselves and replace worn-out cells
• bones are surrounded by calcium phosphate, a substance that makes bones hard. bones also contain collagen, material that provides elasticity. blood vessels supply bones with the nutrients it needs
• labelled skeleton

  
• the end of bones are covered in a smooth, slippery material called cartilage to help cushion the impact of movement
• a place where the end of two bones come together is a joint. most joints allow movement
• joints have synovial fluid to lubricate the ends of bones and allow them to slide over each other freely
• types of joints:

  • hinge joints
  • ball and socket joints
  • pivot joints
  • saddle joints
• hinge joints:

  • the ends of the bones are shaped so movement is allowed in only one plane > backwards and forwards (like the hinge of a door)

  
• ball and socket joints:

  • bone has ball shaped surface that fits into an area like a socket in another bone. can complete all types of movement (found in hip and shoulders)

  
• pivot joints:

  • a ring shaped bone moves around a finger shaped like bone, allowing wide range of movement (joint at base of skull)

  
• saddle joints:

  • allows movement is two directions, but not as much as ball and socket joint
  • found in ankles and base of thumb

  
• ligaments:

  • bands of tough, flexible tissue that hold bones in a joint together
  • prevent bones of joint moving too far apart from each other
• muscles move bones

  muscles are tissues that are able to contract and be stretched

  everyone has 640 muscles
• tendons: tissues that attach muscles to bones and hold them in place
• muscles can only pull, not push, therefore, another muscle is required to return the bone to its original position. this is why your muscles are arranged in antagonistic pairs that work in opposition together
• antagonistic muscles: muscles that work in pairs to oppose each other's actions to return a limb to its original position
• an example of antagonistic muscles in your upper arm are your biceps and triceps