1. The Skeletal System
Unit 8a

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

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

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

5. 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.

6. 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

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

8. 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

9. 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

10. Bone Tissue
Normal Osteoporosis

11. 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

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

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

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

15. Appendicular (yellow)
Axial (orange)

16. 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:

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

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

19. 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

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

21. 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

22. F. Facet joints
1. Stabilizing joints
2. Vertebrae