1. Bones: The Living Framework of the Human Body Eva L. Murdoch, PhD Assistant Professor Department of Natural Sciences Joliet Junior College http://www.youtube.com/watch?v=FufL80hJsP8

2. The Skeleton Provides structural support for the entire body Stores minerals Protects soft tissues Houses red and yellow bone marrow Serves as levers, on which skeletal muscles pull to generate motion

3. Bone Formation and Growth Bone formation – 6 weeks (embryo 0.5”) Bone growth – Continues during development in utero – Continues through childhood – Stops at about age 25 Hormonal regulation – Growth hormone & Thyroxin – stimulate bone cells to produce bone matrix  growth – Sex hormones (estrogen & testosterone) speed up bone synthesis at puberty  growth stops within few years

4. The Human Body The human body: collection of cells and cell products -Cells: smallest living unit performing vital functions -Cell products: non-living, often proteins, also perform vital functions

5. Bone Tissue Living tissue composed of: -Several cell types – osteocytes, osteoblasts, osteoclasts -Matrix - cell products (collagen fibers) and inorganic salts (calcium phosphate)

7. Matrix: Protein-Crystal Combination: -Collagen fibers: exceptionally strong protein, when subjected to tension – stronger than steel -Calcium phosphate crystals: very hard, withstanding compression, but brittle when exposed to twisting Bone Cells: -Osteocytes: maintain protein and mineral content of bone matrix -Osteoblasts: produce bone matrix -Osteoclasts: remove and recycle bone matrix Bone Tissue Ca 3 (PO 4 ) 2

8. Ca 2+ Bone: – Strong, somewhat flexible and highly resistant to shattering. – On par with the best steel- reinforced concrete – Even better, bone undergoes changes (remodeling), and can repair itself after injury Bone Tissue

9. Bone Remodeling Maintaining bone mass is a balance between bone cells creating bone matrix and bone cells dissolving bone matrix. −Recycle & renewal of bone matrix – Maintenance of mineral reserve, supply of minerals in body fluids (blood) −Involves osteocytes, osteoblasts, and osteoclasts Turnover rate: varies −Deposition > removal, bone  stronger −Deposition < removal, bone  weaker Heavy-metal ion deposition into bone matrix – Lead (Pb), cobalt (Co), uranium (U), plutonium (Pu)

10. Bone: Calcium Homeostasis Calcium – essential ion for all cells −Bones: calcium reserve −Calcium homeostasis: maintenance of sufficient calcium ion level in blood 1.Calcium: high in blood −Calcitonin: decrease of calcium in blood, resulting in increased bone production 2.Calcium: low in blood −Parathyroid Hormone: increase of calcium in blood, due to an increase in bone breakdown

11. The Effects of Exercise on Bone Bone adapts to physical stress: – Mineral crystals in bone matrix create small electrical currents Osteoblasts: produce bone matrix Electrical currents: repair of severe fractures – Bone surfaces change Thicker, larger bumps & ridges: muscle attachment

12. Bone and Aging Bone: thinner & weaker – Osteopenia – b/n ages 30 & 40 women lose 8% of bone mass/decade, men 3% Mainly at ends of long bones, vertebrae & jaws Causing fragile limbs, reduction in height, and tooth loss – Osteoporosis – age > 45, severe bone loss, affects: 29% women & 18% man Fractures due to normal physical activity (standing) Accelerated in women: loss of estrogen – Cancer (bone marrow, breast and other) – risk factor for osteoporosis osteoclast activating factors

13. Normal spongy bone Spongy bone in osteoporosis  Things I can do to slow down the effects of aging and assure optimum bone mass. Adequate diet Weight bearing exercise (daily) Monitor hormone levels associated with bone mass