The Skeletal System Unit 8a

Bone I. Bone is living tissue A. Two types of bone tissue 1. Compact bone a. Dense, almost solid tissue b. Provides support

2. Spongy bone a. Provides lightweight support b. Hardened fibers interspersed with spaces filled with: Red marrow- produces red blood cells (RBC)

Yellow marrow-stores fat Periosteum-membrane that surrounds bone and contains blood vessels

Dense compact bone forms most of the shaft of a typical long bone, while porous spongy bone forms most of the interior portion at the ends of the bone. A soft tissue called marrow fills some of the spaces in bone tissue.

Rings of bone around the Haversian Canal II. Osteoblasts (young bone cells) lay down new bone A. It secretes layers of collagen fibers on which calcium phosphate is deposited. Rings of bone around the Haversian Canal

III. Bone cells get trapped in spaces in the bone and are called osteocytes. A. Osteocytes get oxygen from nearby blood vessels.

I. Bone is constantly broken down and replaced. Osteoporosis I. Bone is constantly broken down and replaced. A. At middle age, replacement slows down. B. Severe bone loss is called Osteoporosis 1. Bone becomes brittle and fragile

2. Women are affected more than men 3. Build bone through calcium intake and exercise during teens and twenties. II. Exercise and an active lifestyle help prevent osteoporosis

Bone Tissue Normal Osteoporosis

The human skeleton is divided into two parts: I. The Axial Skeleton The Skeleton The human skeleton is divided into two parts: I. The Axial Skeleton A. The main axis of the body 1. Skull a. cranium encases brain b. 14 facial bones, 6 middle ear bones

2. Spine a. 33 vertebrae b. spinal cord 3. Rib cage a. 12 pairs of ribs b. Ribs attach to the sternum (breastbone)

II. Appendicular Skeleton A. Appendages: Arms and Legs 1. Pectoral Girdle-shoulder attachment a. 2 scapula (shoulder blades) b. 2 clavicles (collar bones)

2. Pelvic Girdle-hip attachment a. 2 large pelvic bones b. transmit weight to the legs

Appendicular (yellow) Axial (orange)

I. Where two bones meet: joint (articulation) Joints I. Where two bones meet: joint (articulation) A. Most joints permit movement B. Cartilage cushion the joints C. Three types of joints based on movement allowed:

1. Immovable (synarthrodial or fibrous) Held together by tough connective tissue skull 2. Slightly moveable (amphiarthrodial) Held together by cartilage Ribs to sternum

3. Freely moveable (diarthrodial or synovial) permit greatest movement in appendages

II. Several types of freely moveable joints (synovial or diarthrodial) A. Ball and socket (multiaxial) 1. Allows all types of movement 2. Shoulder and hips

B. Hinge Joint 1. Allows bending and straightening 2. Elbows, knees, fingers C. Gliding Joint 1. Allows a sliding motion 2. Wrists and ankles

D. Pivot Joint 1. Allows rotation 2. Top of spine (turning head) E. Saddle Joint 1. Allows rotation, bending, and straightening 2. Base of the thumb

F. Facet joints 1. Stabilizing joints 2. Vertebrae