skeletal system

• major organs of skeletal system

  bone and ligaments
• ligaments


  cords of regular dense fibrous tissue that binds the bone to one another
• bones


  are more complex in structure
• component of the skeletal system

  • cartilages
  • bones
  • tendons
  • ligaments
• catilage 


  hyaline, fibrocartilage, elastic
• bones

  spongy and compact; long, short, flat, irregular
• ligaments


  connect bone to bone
• tendons


  connect muscle to bones
• functions of the skeletal system

  • framework and support
  • protection
  • movement
  • storage
  • produce blood cells
• function of bones

  • support the body
  • protect soft organs
  • allow movement due to attached skeletal muscle
  • store minerals and fats
  • blood cell formation
• adult skeleton

  206 bones
• infant skeleton

  270 bones
• compact bone


  homogenous
• spongy bone

  • small needle-like pieces of bone
  • many open spaces
• long bones

  • longer than they are wide
  • have a shaft with heads at both ends
  • contain mostly compact bone
• short bones

  • cube-shaped
  • contain mostly spongy bone
• flat bone

  • thin, flattened, and usually curved
  • two thin layers of compact bone surround a layer of spongy bone
• irregular bone

  • irregular shape
  • do not fit into other bone classification
• anatomy of a long bone

  • diaphysis
  • epiphysis
  • epiphyseal plate
  • epiphyseal line
  • periosteum
  • sharpey's fibers
  • endosteum
  • articular cartilage
  • medullary cavity
• diaphysis

  • shaft
  • composed of compact bone
• epiphysis

  • ends of the bone
  • composed mostly of spongy bone
• epiphyseal plate

  • flat plate of hyaline cartilage
  • seen in young, growing bone
• epiphyseal line

  • remanant of the epiphyseal plate
  • seen in adult bones
• periosteum

  • outside covering of the diaphysis
  • fibrous connective tissue membrane
• sharpey's fiber / perforating


  secure periosteum to underlying bone
• endosteum


  covers internal bone surface
• articular cartilage

  • covers the external surface of the epiphysis
  • made of hyaline cartilage
  • decreases friction at joint surfaces
• medullary cavity

  • cavity inside of the shaft
  • contains yellow marrow (mostly fat) in adults
  • contains red marrow (for blood cell formation) in infants
• lacunae

  • cavities contaning bone cells (osteocytes)
  • arranged in concentric rings
• lamellae

  • rings around the central canal
  • site of lacunae
• canaliculi

  • tiny canals
  • radiate from the central canal to lacunae
  • form a transport system conneting all bone cells to a nutrient supply
• growth

  occurs in terms of:

  • length
  • articular cartilage
  • width
• epiphyseal plates (growth development)

  • allow for lengthwise growth of long bones during childhood
  • new cartilage is continously formed
  • older cartilage becomes ossified
  • cartilage is broken down
  • enclosed cartilage is digested away, opening up a medullary cavity
  • bone replaces cartilage through the action of osteoblast
• bone remodeling

  • bone remodeling is performed by both osteoblasts and osteoclasts
  • bones are remodeled and lengthened until growth stops
• bones are remodeled in response to two factors:

  • blood calcium levels
  • pull of gravity and muscles on the skeleton
• factors affecting bone growth

  • nutrition
  • hormones
  • bone cells
• nutrition

  • vitamin c - collagen synthesis of osteoblast
  • vitamin d - normal absorption of calcium in the intestines
• hormones

  • growth hormones
  • thyroid hormones
  • sex hormones
• types of bone cells

  • osteocytes
  • osteoblasts
  • osteoclasts
• osteocytes


  mature bone cells