1. Bones Structure, Remodeling, Homeostatic Imbalances

2. Classification of Bones Long: longer than wide Short: roughly cube- shaped Flat: flat and slightly curved Irregular: everything else

6. Bone is always changing Fetus skeleton is a cartilage template, replaced by bone Ossification (bone formation) continues until about age 16 in females and 21 in males Long bones stop growing in length when the epiphyseal plate ossifies

7. Fetal Skeleton

8. Cartilage is replaced by bone

9. Longitudinal vs Appositional growth

10. Bones continue to change or remodel because of: Hormones: growth and sex Stresses and gravity (femur is replaced every 6 months) Body’s need for calcium

11. Types of bone cells: Osteoblasts: Bone-forming cells that secrete matrix, then get trapped in it and turn into: Osteocytes: Mature bone cells imbedded in matrix of flexible collagen and hydroxyapatite (Ca salt)

12. Bone remodels due to osteoblasts and osteoclasts Osteoclasts: Bone destroying cells, secrete enzymes that destroy matrix and break down calcium for the blood Osteoclasts: Bone destroying cells, secrete enzymes that destroy matrix and break down calcium for the blood

13. Balancing blood calcium

14. Bone Fractures A break in a bone Types of bone fractures –Closed (simple) fracture – break that does not penetrate the skin –Open (compound) fracture – broken bone penetrates through the skin Treatment: closed or open (surgery) reduction and immobilization (cast) –Reduction = Realignment of the bone

15. Types of Fractures

16. Repair of fractures Hematoma (blood-filled swelling) is formed Break is splinted by fibrocartilage to form a callus Fibrocartilage callus is replaced by a bony callus Bony callus is remodeled to form a permanent patch

17. Steps in healing of fractures

18. Bone Problems Osteoporosis: bone mass is lost resulting in porous bones that are easily broken, common in the elderly

19. Osteomalacia Softening of bones due to lack of calcium Called rickets in children

20. Paget’s Disease Abnormal growth and resorption of bone Possibly caused by a virus Mostly affects hips, shoulders and vertebrae

21. Spinal curvatures Scoliosis: lateral curvature Lordosis: “swayback”, common in pregnant women and “beer bellies” Kyphosis: “humpback”, common in osteoporosis

25. X ray of osteoporosis

26. X Ray Quiz