skeletal system

• Parts of the skeletal system

  • Bones (skeleton)
  • Joints
  • Cartilages
  • Ligaments (bone to bone)(tendon=bone to muscle)
• Divisions of the skeletal system

  • Axial skeleton: bones of the skull, vertebral column, and rib cage
  • Appendicular skeleton: bones of the upper and lower limbs, shoulder and hip
• Functions of Bones


  • Support of the body
  • Protection of soft organs
  • Movement due to attached skeletal muscles
  • Storage of minerals and fats
  • Blood cell formation
• Spongy bone


  • Small needle-like pieces of bone
  • Many open spaces
• Classification of Bones on the Basis of Shape

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
• Long bones


  • Typically longer than wide
  • Have a shaft with heads at both ends
  • Contain mostly compact bone
• Long bones


  • Femur, humerus
• Short bones


  • Generally cube-shape
  • Contain mostly spongy bone
• Short bones


  • Carpals, tarsals
• Flat bones


  • Thin and flattened
  • Usually curved
  • Thin layers of compact bone around a layer of spongy bone
• Flat bones


  • Skull, ribs, sternum
• Irregular bones


  • Irregular shape
  • Do not fit into other bone classification categories
• Irregular bones


  • Vertebrae and hip
• Structures of a Long Bone

  • Periosteum
  • Sharpey's fibers
  • Arteries
  • Articular cartilage
  • Medullary cavity
• Periosteum


  • Outside covering of the diaphysis
  • Fibrous connective tissue membrane
• Sharpey's fibers


  Secure periosteum to underlying bone
• Articular cartilage


  • Covers the external surface of the epiphyses
  • Made of hyaline cartilage
  • Decreases friction at joint surfaces
• Medullary cavity


  • Cavity of the shaft
  • Contains yellow marrow (mostly fat) in adults
  • Contains red marrow (for blood cell formation) in infants
• Bone Markings


  • Projections and processes – grow out from the bone surface
  • Depressions or cavities – indentations
• Changes in the Human Skeleton

  1. In embryos, the skeleton is primarily hyaline cartilage

  2. During development, much of this cartilage is replaced by bone

  3. Cartilage remains in isolated areas
• Types of Bone Cells

  • Osteocytes
  • Osteoblasts
  • Osteoclasts
• Osteocytes


  Mature bone cells
• Osteoblasts


  Bone-forming cells
• Osteoclasts


  • Bone-destroying cells
  • Break down bone matrix for remodeling and release of calcium
• Repair of Bone Fractures

  1. Hematoma (blood-filled swelling) is formed

  2. Break is splinted by fibrocartilage to form a callus

  3. Fibrocartilage callus is replaced by a bony callus

  4. Bony callus is remodeled to form a permanent patch
• Parts of the Axial Skeleton

  • Skull
  • Vertebral column
  • Bony thorax
• The Skull


  • Two sets of bones: Cranium and Facial bones
  • Bones are joined by sutures
  • Only the mandible is attached by a freely movable joint
• The hyoid bone is the only bone that does not articulate (move) with another bone
• Fontanelles

  • Fibrous membranes connecting the cranial bones
  • Allow the brain to grow
  • Convert to bone within 24 months after birth
• The Vertebral Column


  • Vertebrae separated by intervertebral discs
  • The spine has a normal curvature
  • Each vertebrae is given a name according to its location
• Parts of the Bony Thorax

  • Sternum
  • Ribs
  • Thoracic vertebrae
• Parts of the Appendicular Skeleton

  • Limbs (appendages)
  • Pectoral girdle
  • Pelvic girdle
• The Pectoral (Shoulder) Girdle

  • Composed of two bones: Clavicle and Scapula
  • These bones allow the upper limb to have exceptionally free movement
• Bones of the Upper Limb

  • Humerus
  • Ulna
  • Radius
  • Carpals
  • Metacarpals
  • Phalanges
• Bones of the Pelvic Girdle

  • Hip bones
  • Composed of three pair of fused bones: Ilium, Ischium, Pubic bone
  • The total weight of the upper body rests on the pelvis
  • Protects several organs: Reproductive organs, Urinary bladder, Part of the large intestine
• There are gender differences in the pelvis
• Bones of the Lower Limbs

  • Femur
  • Tibia
  • Fibula
  • Talus
  • Metatarsals
  • Phalanges
• Functional Classification of Joints

  • Synarthroses – immovable joints
  • Amphiarthroses – slightly moveable joints
  • Diarthroses – freely moveable joints
• Structural Classification of Joints

  • Fibrous joints
  • Cartilaginous joints
  • Synovial joints
• Fibrous Joints


  Bones united by fibrous tissue – synarthrosis or largely immovable