Session4

Dr. Maria Zahiri

↑ osteoblast ↓ osteoclast

osteoblast ↑ osteoclast

Vitamin D: increases calcium from gut

Parathyroid hormone (PTH): increases blood calcium (some of this comes out of bone)

Calcitonin: decreases blood calcium (opposes PTH)

Growth hormone & thyroid hormone: modulate bone growth

Sex hormones: growth spurt at adolescense and closure of epiphyses

Disorders of cartilage and bone Defective collagen

Numerous genetic disorders eg. Osteogenesis imperfecta (brittle bones) – AD (autosomal dominant) eg. Ehlers-Danlos (rubber man)

Defective endochondral ossification eg. Achondroplasia (short –limb dwarfism) – AD

Inadequate calcification (requires calcium and vitamin D) Osteomalacia (soft bones) in adults Rickets in children

Disorders of cartilage and bone Defective collagen

Osteogenesis imperfecta (OI - brittle bones) congenital bone disorder brittle bones that are prone to fracture defective connective tissue, or without the ability to make

it usually deficiency of Type-I collagen

Disorders of cartilage and bone Defective collagen

Ehlers-Danlos (rubber man) (EDS) is an inherited connective tissue disorder EDS is caused by a defect in the synthesis of collagen,

Disorders of cartilage and bone

Defective endochondral ossification Achondroplasia (short –limb dwarfism) – AD caused by a change in the DNA for

fibroblast growth factor receptor 3 (FGFR3), which causes an abnormality of cartilage formation

Disorders of cartilage and bone

Inadequate calcification (requires calcium and vitamin D) Osteomalacia (soft bones) in adults Rickets in children is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available

phosphorus and calcium, or because of overactive resorption of calcium from the

bone as a result of hyperparathyroidism (which causes hypercalcemia,

Pagets disease – excessive turnover, abnormal bone

Osteosarcoma – bone cancer, affecting children primarily

Osteoporosis – usually age related, esp. females Low bone mass and increased fractures Resorption outpaces bone deposition

Normal bone

Osteoporotic bone

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