1. Chapter 6 The Skeletal System

2. FUNCTIONS OF THE SKELETAL SYSTEM
Supports and gives shape to the body
Protects internal organs
Helps make movements possible
Stores calcium
Hemopoiesis, or blood cell formation

3. TYPES OF BONES
Four major types, according to overall shape of the bone
Long—Example: humerus (upper arm)
Short—Example: carpals (wrist)
Flat—Example: frontal (skull)
Irregular—Example: vertebrae (spinal cord)
Some also recognize a sesamoid (round) bone category
Example: patella (kneecap)

4. STRUCTURE OF LONG BONES
Structural components (Figure 6-1)
Diaphysis or shaft—hollow tube of hard compact bone
Medullary cavity—hollow area inside diaphysis bone that contains yellow marrow
Epiphyses, or ends of the bone—spongy bone that contains red bone marrow
Articular cartilage—covers epiphyses and functions as a cushion
Periosteum—strong membrane covering bone everywhere except at joint surfaces
Endosteum—lining of medullary cavity

6. MICROSCOPIC STRUCTURE OF BONE AND CARTILAGE
Bone types (Figure 6-2)
Spongy
Texture results from needlelike threads of bone called trabeculae surrounded by a network of open spaces
Found in epiphyses of bones
Spaces contain red bone marrow
Compact
Structural unit is an osteon—calcified matrix arranged in multiple layers or rings called concentric lamella
Composed of osteocytes, lacunae, and canaliculi
Covered by periosteum

8. MICROSCOPIC STRUCTURE OF BONE AND CARTILAGE
Cartilage (Figure 6-4)
Cell type called chondrocyte
Matrix is gel-like and lacks blood vessels

10. BONE FORMATION AND GROWTH (Figures 6-5 and 6-6)
Early bone development (before birth) consists of cartilage and fibrous structures
Cartilage models gradually replaced by calcified bone matrix—process called endochondral ossification
Osteoblasts form new bone, and osteoclasts resorb bone

13. DIVISIONS OF SKELETON
Skeleton composed of the following divisions and their subdivisions:
Axial skeleton
Skull
Spine (vertebral column)
Thorax
Appendicular skeleton
Upper extremities, including shoulder (pectoral) girdle
Lower extremities, including hip (pelvic) girdle
Location and description of bones—see Figures 6-7 to 6-17 and Tables 6-2 to 6-6