skeletal system and Bones

Skeletal system

  • bones

  • joints

  • cartilage

  • tendons (bone to muscle)

  • ligaments (bone to bone)

Function of the Skeletal system

  • support of the body

  • protection of soft organs

  • movement due to attached skeletal muscles

  • storage of minerals and fats

  • blood formation

Types of Bone tissue

  • compact bones: the hard outer layer of bone

  • spongy bones: less dense, small needle-like pieces of bone (trabeculae)

    • Many open scales

  • Bone marrow: soft tissue inside the bone that produces blood cells

Classification of Bone

  • bones are classified according to shape

  1. Long Bones

    • typically longer than wide

    • have a shaft with heads at both ends

    • contain mostly compact bone

    • examples: femur, humerus

  2. short bones

  • generally cube-shaped

  • contain most spongy bone

  • examples: carpals, tarsals

  1. flat bones

  • thin and flattened

  • usually curved

  • thin layers of compact bone around a layer of spongy bone

  • examples: skull, ribs, and sternum

Gross Anatomy of Long Bone

  • diaphysis —> shaft

  • compose of compact bone

  • location of yellow marrow (fat)

Epiphysis - end of the bone

  • composed mostly of spongy bone

  • location of red marrow (blood formation)

Periosteum

  • outside covering of the diaphysis

  • fibrous connective tissue membrane

Arteries

  • supply bone cells with nutrients

Articular cartilage

  • covers the external surface of the epiphysis

  • 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

Microscopic Anatomy of the Bone

  • osteon (Haverian System)

    • a unit of bone

  • Central (Haversian) canal

    • opening in center of an osteon

    • carries blood vessels and nerves

  • Lacunae

    • cavities containing bone cells (osteocytes)

    • arranged in concentric rings

  • Lamellae

    • rings around the central canal

    • sites of lacunae

  • canaliculi

    • tiny canals

    • radiate from the central canal to lacunae

    • form a transport system

      Ossification: Bone Growth

    • epiphyseal plates allow for the growth of long bone during childhood

      • new cartilage is continuously formed

      • older cartilage becomes ossified (changed to bone)

      • cartilage is broke down

      • bone replaces cartilage

        Bones are remodeled and lengthened until growth stops

      • Bones change shape somewhat

      • bones grow in width

        Types of Bone cells

      • Osteocytes

        • Mature bone cells

          Osteoblasts

          • Bone forming cells fro bone growth

            Osteoclasts

          • Bone destroying cells

          • Break down bone matric for remodeling and release of calcium

            Bone remodeling is a process done by both osteoblasts and osteocyts

            Bone fractures

          • a break in a bone

          • types of bon fractures

          • close (simple) fracture - break that does not penetrate the skin

          • open (compound) fracture - broken bone penetrates through the skin

          • Bone fractures are treated by reduction and immobilization

          • bone realignment of the bone

            Repair of bones

          • Hematoma (blood-filled swelling) is formed

          • Break is splinted (immobilized) by fibrocartilage to form a callus

          • fibrocartilage callus is replaced by a bony callus

          • bony callus is remodeled to form a permanent patch



          • Describe the functions of the skeletal system

          • differentiate between the 4 types of bones, given an example of each

          • explain how ossification works

          • compare the 3 types of bone cells

          • summarize how bone fractures are repaired