C HAPTER 6.3: S KELETAL S YSTEM

I NJURY AND R EPAIR Fracture—any crack or break in bone Repair: 4 months to over 1 year Fracture hematoma forms Large blood clot Closes off injured blood vessels Periosteum and endosteum cells divide New cells move to fracture zone Produce hyaline cartilage Spongy bone replaces hyaline cartilage (takes long time) Compact bone replaces spongy bone

T YPES OF F RACTURES Closed (Simple) Completely internal No break of skin

T YPES CONT … Open (compound) Break through skin Possible infection or prolonged bleeding

T YPES CONT … Pott’s Fracture At ankle Involves both the tibia and fibula

T YPES CONT … Colle’s Fracture Distal radius Ex: Cushion a fall

T YPES CONT … Transverse Break along a long axis Spiral Twisting along length of bone Comminuted Shatter into fragments

A GING Become thinner and weaker Osteopenia—inadequate ossification 30-40: Reduction in bone mass Osteoblasts decrease Women lose 8% of bone mass/decade Men lose 3%/decade

O STEOPOROSIS Reduction in bone mass past normal Sex hormones help maintain bone mass Over 45: 29% of females and 18% of males have osteoporosis In females menopause causes decreased estrogen Bones break easily and do not heal well Estrogen supplements, diet high in calcium and exercise slow the disease

S KELETAL DIVISION 206 Bones Axial Skeleton (80 Bones) Skull Thoracic Cage (ribs) Vertebral Column Appendicular Skeleton Pectoral and pelvic girdles Arms and legs

F IGURE 6.8