The Skeletal System


  • There are 206 bones in the human body


Functions of the skeleton:

  • Protection - protects the important internal organs from injury (eg. Cranium and rib cage)

  • Support - framework - stand and walk. Ligament (bone on bone) internal organs - back and sternum

  • Blood cell production - red marrow (blood cells, red and white) and yellow marrow (stores fat, no blood cells)

  • Movement - tendons (muscle to bone). Periosteum membrane on outside of bone

  • Shape - long/short bones, sports - can change to be more suited



Types of bones:

  • Long bone

  • Irregular bone

  • Smooth / flat bone

  • Short / sesamoid bone




The axial skeleton

  • Forms the main core of the skeletal system and is more rigid than the appendicular skeleton

  • Comprises of: vertebral column (spine), cranium, thoracic (rib cage), sternum

The appendicular skeleton

  • Comprises of the shoulder girdle and the pelvic girdle

  • Clavicle, scapula, arms, legs, pelvic bone




Long bone - femur (levers for movement, supports weight, structure)

Irregular bone - pelvis (protecting internal organs and structure)



Smooth bone - cranium (low-friction surface for movement)

Short bone - carpels (provide stability, support, limited movement)



Bones and joints:

Freely Moveable Joints = Synovial Joints ->


 

The hinge joint:

  • Knee

  • Elbow

  • Flexion and extension

Ball and socket joint:

  • Shoulder

  • Hip

  • Flexion, extension, abduction, adduction, rotation



Flexion - when you bend a joint and the angle decreases

Extension - When you straighten a joint and the angle increases

Abduction - movement away from your medial line (center of body)

Adduction - movement back toward your medial line

Rotation - circular motion of a whole limb

Plantar Flexion - only occurs in the ankle, when foot pushes down and toes point up

Dorsi Flexion - only occurs in ankle, when foot is lifted towards shin and toes are lifted upwards