Bones and Joints

• 4 main functions of the skeleton:

  1. Movement
  2. Support
  3. Protection
  4. Physiological Functions
• Bone Structure:

  • Diaphysis - shaft
  • Epiphyses - ends
  • Metaphysis - location of growth plate
• Compact or Cortical Bone:

  • 80% of bone mass
  • Mechanical function
  • External surface
• Spongy or Cancellous or Trabecular Bone:

  • 20% of bone mass
  • Lattice of fine plates, spaces filled with bone marrow
  • Reduces mass without losing strength
• Levers:

  • Resistance - weight, body part
  • Fulcrum - joints
  • Effort - muscles
• 1st Class Levers: Pivot in middle

  e.g. nodding
• 2nd Class Lever: Resistance in middle

  e.g. going on tiptoes
• 3rd Class Levers: Effort in middle

  e.g. most other joints
• Axial Skeleton consists of head, neck and trunk. There are 74 bones
• Appendicular Skeleton consists of the arms and legs. There are 126 bones
• Flat Bones

  • Thin and curved
  • point of attachment for muscles
  • protect internal organs
  • e.g. sternum
• Short Bones

  • Cube shaped
  • Limited motion
  • e.g. carpals
• Long Bones

  • cylinder shaped
  • function as levers
  • e.g. femur
• Irregular Bones:

  • Complex shape
  • Protect internal organs from compressive forces
  • e.g. vertebrae
• Sesamoid Bones

  • embedded within tendons
  • protect from stress
  • e.g. patella
• Joints facilitate movement between bones. They allow force to be transmitted from one bone to another
• Articular Surface: point between 2 skeletal bones
• Synarthroses: Joints that don't move, e.g. sutures of skull
• Amphiarthroses: Joints that move slightly to attenuate force
• Joint stability provided by:

  • shape of bones
  • arrangement of muscles and ligaments
  • other connective tissue
• Articular cartilage: layer of connective tissue protecting ends of articulating bones
• Articular capsule: double layered membrane surrounding synovial joint
• Synovial membrane: lines surface of capsule, secretes synovial fluid
• Diarthroses: joints that move freely
• 6 types of diarthroses:

  1. Gliding
  2. Hinge
  3. Pivot
  4. Condyloid
  5. Saddle
  6. Ball and Socket
• Gliding Joint

  
• Hinge Joint

  
• Pivot Joint

  
• Condyloid Joint

  
• Saddle Joint

  
• Ball and Socket Joint

  
• Osteoblasts do bone formation
• Osteoclasts do bone reabsorption