1.  Skeleton is formed from two hard connective tissues: bone and cartilage  Five basic functions:  1. provides support for soft tissues and organs  2. provides protection for soft tissues and organs  3. allow for movement  4. involved in storing minerals (calcium and phosphorus) + 5. blood cell formation

2.  Types of Bones: 1. Compact Bone: * dense and looks smooth and homogenous 2. Spongy Bone: * composed of small needlelike pieces of bone and lots of open space

3. Groups of Bones: 1. Long Bones: a. longer than they are wide b. have a shaft with heads at both ends c. mostly compact bone d. all bones of the limbs, except the wrist and ankle 2. Short bones: a. Generally cube shaped b. Bones of the wrist and ankle c. Sesamoid bones (patella or kneecap)

4. Groups of Bones contd.: 3. Flat Bones: a. Thin, flattened, usually curved b. Two thin layers of compact bone sandwiching a layer of spongy bone c. Most bones of the skull, the ribs, and the sternum 4. Irregular Bones: a. Bones that do not fit one of the preceding categories b. Consists of the vertebrae and the hip bones

5.  Gross Anatomy Diaphysis: - shaft that makes up most of the bone’s length and is composed of compact bone - covered and protected by the periosteum (fibrous connective tissue membrane)

6.  Epiphyses: - ends of the long bone - consists of a thin layer of compact bone enclosing an area filled with spongy bone - covered with articular cartilage

7.  Epiphyseal Line: - thin line of bony tissue spanning the epiphysis - remnant of the epiphyseal plate (seen in young, growing bone) - Epiphyseal plate causes lengthwise growth of a long bone

8. Adults: - primarily a storage area for adipose tissue (yellow marrow) Infants: - forms blood cells and red marrow is found here

9.  Mature Bone Cells: Osteocytes found in tiny cavities within the matrix called lacunae Lacunae arranged in concentric circles called lamellae around central (Haversion) canals Each complex consisting of central canal and matrix rings is called an osteon or Haversion system Tiny canals called canaliculi radiate outward from the central canals to all lacunae