Biology

• Skeletal system


  Structure of the skeleton

  
• Structure of the skeleton

  • 206 bones
  • Axial skeleton - supports central axis of the body (skull, vertebral, ribcage)
  • Appendicular skeleton - arms, legs, bones in pelvis, shoulder area

  
• Functions of skeletal system

  • Provide support for the whole body
  • Protect internal organs
  • Assist movement
  • Store minerals
  • Place for blood cell formation

  
• Bones


  Solid network of living cells and protein fibers surrounded by deposits of calcium salts

  
• Periosteum


  Membrane that covers the outer surface of bones

  
• Haversian canals


  Minute tubes that contain bone's blood supply and nerves
• Osteon


  Basic unit of structure of compact bone

  
• Compact bones


  Dense compact bone, found under periosteum

  
• Soft bones


  Tiny structures arranged in a way that can support a lot of force
• Bone marrow


  Soft tissue - yellow stores fat, red produces red blood cells
• Where can you find cartilage?
• Bone remodelling and repair

  1. Remodelling of Bone - process of repairing old cells with new cells

  2. Osteoclast - cells that breakdown bone cells, replaced by new bone tissue

  3. Osteoporosis - osteoclasts break down bone much faster than osteoblasts rebuild it
• Joints


  Contain connective tissues that hold bones together

  
• Types of joints


  • Immoveable (fixed joints) - no movement, bones sutured together
  • Slightly moveable - permit small amount of movement
  • Freely moveable joints - permit movement in two or more directions
• Freely moveable joints


  • Ball and socket
  • Pivot
  • Hinge
  • Saddle
• Ball and socket joints


  • Allow the greatest range of movement
  • One end of bone is shaped like a ball, fits into a hollow socket
  • Held together by ligaments and tendons

  
• Two main ball and socket joints

  • Shoulder and hip joints

  
• Hinge joints


  • Allow extensive flexion and extension (bending and straightening) with only a small amount of rotation
  • Like opening and closing of a door
• Examples of hinge joints


  • Elbow and knee joints
• Pivot joints


  • Allow only rotation
  • One bone has a "peg" that fits into a "ring" formed by the other bone

  
• Example of pivot joint


  • Top of spinal column, between axis and atlas bones of the neck
• Saddle joints


  • Allow one bone to slide in two directions
  • Allow movement forward and backwards, and right to left
• Examples of saddle joints

  • Fingers and thumbs
• Ligaments


  Tough, elastic fibres that link bones to bones

  
• Tendons


  Connect muscles to bones
• Cartilage


  Prevents the ends of bones rubbing together at joints, helps lubricate the joint
• Differences between connective tissues

  • Cartilage - flexible, cushions
  • Tendons - attach bone to muscle, non-elastic
  • Ligaments - attach bone to bone, elastic, stabilise

  
• Skeletal muscle characteristics


  • Most are attached by tendons to bones
  • Cells are multinucleate
  • Striated - have visible banding
  • Voluntary - subject to conscious control
  • Cells surrounded by connective tissue - great force, tires easily
• Smooth muscle characteristics


  • Has no striations
  • Spindle-shaped cells
  • Single nucleus
  • Involuntary - no conscious control
  • Found mainly in walls of hollow organs
  • Slow, sustained and tireless
• Cardiac muscle characteristics


  • Has striations
  • Usually has a single nucleus
  • Joined to another muscle cell at an intercalated disc
  • Involuntary
  • Found only in the heart
  • Steady pace
• Classification of muscle


  • Skeletal - striated, multi-nucleated, voluntary
  • Cardiac - striated, 1 nucleus, involuntary
  • Smooth - not striated, 1 nucleus, involuntary
• Function of muscles


  • Produce movement
  • Maintain posture
  • Stabilize joints
  • Generate heat