Remodeling of skeletal structures Bone tissue is constantly being torn down and built up About 10% of bone is replaced every year in an adult skeleton

bone formation bone reabsorption osteoblasts osteoclasts

Hormonal effects osteoblasts osteoclasts Calcitonin (CT) from thyroid bone formation bone reabsorption osteoblasts osteoclasts Calcitonin (CT) from thyroid Parathyroid hormone (PTH) from parathyroid

Age effects Before age 25 osteoblasts osteoclasts bone reabsorption bone formation bone reabsorption osteoblasts osteoclasts Before age 25

Age effects Age 25-50 osteoblasts osteoclasts bone formation bone reabsorption osteoblasts osteoclasts Age 25-50

Age effects Age 50-120 osteoblasts osteoclasts bone formation bone reabsorption osteoblasts osteoclasts Age 50-120

Stress increases bone density Stress effects bone formation bone reabsorption osteoblasts osteoclasts Stress increases bone density

can alter orientation & size of Direction of stress can alter orientation & size of of osteons

Increasing bone stress can reduce or eliminate age-related bone loss

Space travel decreases stress & increases bone loss

Too much stress . . .