1. Osseous Tissue (Bone Tissue)

2. Classification of Bone by Tissue Type Two basic types of Tissue 1. Compact bone Homogeneous Looks “smooth” 2. Spongy bone Small needle-like pieces of bone Many open spaces (like sponge) Keep bones light Figure 5.2b

3. Review: Bone is a type of connective tissue 2 Parts: 1. Cells (living) 2. Matrix (nonliving substance released by cells) A. Fiber B. Ground Substance

4. 1. Cells Osteocytes— mature bone cells Osteoblasts— bone-forming cells (germ cells or “bud” cells) Osteoclasts —bone-destroying cells (“breakers”) A. primarily collagen fibers flexibility tensile strength (the strength to endure stretching forces) B. calcium salts (hardness) contain calcium and phosphorus great compressional strength (the strength to endure squeezing forces) 2. Matrix

5. Bone Remodeling constant balance of bone deposit and removal that occurs throughout your life bone deposit occurs at a greater rate when bone is injured bone resorption allows calcium of degraded bone matrix to move into the blood. About 10% of bone is replaced every year in an adult skeleton

6. bone formation bone reabsorption osteoblastsosteoclasts Maintenance of Bone

7. Control of Remodeling Hormonal – Rising blood Ca 2+ levels trigger the thyroid to release calcitonin – Calcitonin stimulates calcium salt deposit in bone – Falling blood Ca 2+ levels signal the parathyroid glands to release Parathyroid hormone (PTH) – PTH signals osteoclasts to degrade bone matrix and release Ca 2+ into the blood

8. bone formation bone reabsorption osteoblastsosteoclasts Calcitonin (CT) from thyroid Parathyroid hormone (PTH) from parathyroid Hormonal effects

9. bone formation bone reabsorption osteoblastsosteoclasts Before age 25 Increase bone mass

10. bone formation bone reabsorption osteoblastsosteoclasts Age 25-50

11. bone formation bone reabsorption osteoblastsosteoclasts Age 50-on Decrease bone mass

12. bone formation bone reabsorption osteoblastsosteoclasts Stress effects Stress increases bone density

13. http://www.youtube.com/watch?v=yFJ4iswRiu4&feature=related