Bone Formation, Growth, and Remodeling

Bone formation, growth and remodeling The skeleton is formed from two of the strongest and most supportive tissues in the body: Cartilage and Bone

Bone Formation Embryo skeleton made of primarily Hyaline Cartilage

Bone Formation

By birth or shortly after, most hyaline cartilage models are converted to bone except for 2 regions: articular cartilage and epiphyseal plates Cartilage remains only in isolated areas such as the bridge of the nose, parts of the ribs, and the joints (articular cartilage).

Bone Growth

Long Bone Formation and Growth

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Factors Affecting Bone Growth Size and shape of a bone determined genetically but can be modified and influenced by nutrition and hormones Nutrition Lack of calcium, protein and other nutrients during growth and development can cause bones to be small 10

Factors Affecting Bone Growth Vitamin D Necessary for absorption of calcium from intestines Can be eaten or manufactured in the body Rickets: lack of vitamin D during childhood; bones soften Osteomalacia: lack of vitamin D during adulthood leading to softening of bones Vitamin C Necessary for collagen synthesis by osteoblasts Scurvy: due to deficiency of vitamin C Lack of vitamin C also causes wounds not to heal, teeth to fall out 11

Calcium regulation is a negative feedback mechanism 12

Calcium Homeostasis 13

Correction for Hypercalcemia 14

Bone Growth at an Epiphyseal Cartilage 15

Bone Remodeling

Blood Calcium Levels

PTH (ParaThyroid Hormone) PTH determines when or if bone is to be broken down or formed in response to the need for more or fewer calcium ions in the blood. Stresses of muscle pull and gravity determine where bone matrix is to be remodeled

Effects of Aging on Skeletal System Bone matrix decreases. More brittle due to lack of collagen; but also less hydroxyapatite. Bone mass decreases. Highest around 30. Male bone mass denser due to testosterone and greater weight. African Americans and Hispanics have higher bone masses than Caucasians and Asians. Rate of bone loss increases 10 fold after menopause. Cancellous bone lost first, then compact. 19

Effects of Aging on Skeletal System Increased bone fractures Bone loss causes deformity, loss of height, pain, stiffness Stooped posture Loss of teeth 20

Types of Bone Cells  Osteocytes - Mature bone cells  Osteoblasts - Bone-forming cells  Osteoclasts - Bone-destroying cells  Break down bone matrix for remodeling and release of calcium  Bone remodeling is a process by both osteoblasts and osteoclasts