Download Defective endochondral ossification

Session4
Dr. Maria Zahiri
↑ osteoblast
↓ osteoclast
osteoblast
↑ osteoclast
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Vitamin D: increases calcium from gut
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Parathyroid hormone (PTH): increases blood calcium (some of
this comes out of bone)
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Calcitonin: decreases blood calcium (opposes PTH)
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Growth hormone & thyroid hormone: modulate bone growth
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Sex hormones: growth spurt at adolescense and closure of
epiphyses
Disorders of cartilage and bone
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Defective collagen
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Defective endochondral ossification
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Numerous genetic disorders
eg. Osteogenesis imperfecta (brittle bones) – AD (autosomal dominant)
eg. Ehlers-Danlos (rubber man)
eg. Achondroplasia (short –limb dwarfism) – AD
Inadequate calcification (requires calcium and vitamin
D)
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Osteomalacia (soft bones) in adults
Rickets in children
Disorders of cartilage and bone
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Defective collagen
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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
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Defective collagen
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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
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Defective endochondral ossification
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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
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Inadequate calcification (requires calcium and vitamin
D)
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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,
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Pagets disease – excessive turnover, abnormal bone
Osteosarcoma – bone cancer, affecting children
primarily
Osteoporosis – usually age related, esp. females
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Low bone mass and increased fractures
Resorption outpaces bone deposition
Normal bone
Osteoporotic bone
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