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 collagenType-I collagen

Disorders of cartilage and bone  Defective collagen  Ehlers-Danlos (rubber man)  (EDS) is an inherited connective tissue disorderinheritedconnective tissue  EDS is caused by a defect in the synthesis of collagen,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 formationfibroblast growth factor receptor 3cartilage

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 bonesbones  caused by defective bone mineralizationbone mineralization  secondary to inadequate amounts of available phosphorus and calcium,phosphoruscalcium  or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism (which causes hypercalcemia,resorptionhyperparathyroidismhypercalcemia

 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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