musculoskeletal system

• Parts of bone


  • Compact bone
  • Spongy bone
  • Medullary cavity
  • Trabecule
  • Epiphyseal line
  • Cartilage
• Compact bone


  Usually forms the shaft of the bone, gives the bone its strength
• Spongy bone


  Has a more open structure, found inside the compact bone
• Medullary cavity


  Found inside the bone, forms the middle part, has a blood supply network and houses bone marrow
• Trabecule


  The enlarged spongy ends of a bone, where bone enlargement takes place
• Epiphyseal line


  Formed between the growth plates and the shaft of the bone
• Cartilage


  Protective layer which coats the ends of the bones, aids articulation
• Bone cells

  • Osteoblasts
  • Osteocytes
  • Osteoclasts
• Osteoblasts


  Cells which gradually invade the cartilage, depositing mineral salts such as calcium phosphate
• Osteocytes


  What osteoblasts become known as, containing the mineral deposits, help maintain the bone as it forms and increases in size
• Osteoclasts


  Remove bone by using enzymes to dissolve the bone salts, work with osteoblasts to re-sculpt the skeleton
• Oestrogen levels drop after menopause

  Osteoblast activity drops, bone becomes thinner and more brittle (OSTEOPOROSIS)
• Types of synovial joints

  • Pivot joints
  • Hinge joints
  • Saddle joints
  • Plane joints
  • Condyloid joints
  • Ball-and-socket joints
• Pivot joints


  Allow for rotation around an axis, e.g. between the first and second cervical vertebrae, neck
• Hinge joints


  Work like a door hinge, e.g. the elbow
• Saddle joints


  Articulation between the trapezium carpal bone and the first metacarpal bone at the base of the thumb
• Plane joints


  Allow for limited gliding movements between bones, e.g. between the tarsal bones of the foot
• Condyloid joints (sliding/gliding) 


  The radiocarpal joint of the wrist
• Ball-and-socket joints


  The hip and shoulder joints
• Components of a synovial joint


  • Muscle
  • Bone
  • Ligaments
  • Tendons
  • Cartilage
  • Synovial capsule
  • Synovial fluid
  • Joint capsule
• Muscle


  Necessary for movement, contract and relax to move the joint
• Bone


  Provides the framework and support for the attachment of muscles and other tissues
• Ligaments


  Attach one bone to another
• Tendons


  Attach a muscle to a bone
• Cartilage


  Reduces friction and absorbs shock in a joint, allowing it to move smoothly
• Synovial capsule


  Secretes synovial fluid and maintains joint stability
• Synovial fluid


  Provides lubrication and nourishes the joint
• Joint capsule


  An envelope-like sac that forms a sleeve around a synovial joint
• Muscles have to work in pairs to bring about opposite actions as they can only 'pull' when they contract - they do not 'push'
• Antagonistic muscles


  Work in pairs, create movement when one contracts and the other (the antagonist) relaxes
• Antagonistic muscles


  • Biceps and triceps in the arm
  • Quadriceps and hamstrings in the leg
• When a muscle contracts to move a joint it is the tendon that pulls on the bone