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Flashcards in Ossification And Bone Disease Deck (14)
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Describe intramembranous ossification as related to bone growth

1) starts as highly vascularised connective tissue
2) focus of activity is at primary centre of ossification
3) mesenchymal cells differentiate into osteoblasts, surrounded by collagen fibres and ground substance
4) osteoblasts secrete uncalcified matrix (osteoid) which later calcifies
5) osteoblasts become osteocytes (entombed in osteoid)


Where does intramembranous ossification take place and what does it form?

Withing condensations of mesenchymal tissue
Forms flat bones e.g. Skull, maxilla, mandible, pelvis, clavical


Describe the process of endochondral ossification

Hyaline cartilage acts as trmplate, it is reabsorbed s d replaced by bone
Begins as primary centre for ossification in the diaphysis shaft and later at secondary centres at each end (ephysis)
Growth in diameter by deposition of bone at periphery of shaft
Growth in length occurs at cartilaginous ephysial growth plates


Where does endochondrial ossification occur and what does it form?

In hyaline cartilage within bones at growth regions
Most bones develop like this


Describe osteogenesis imperfecta

Rare genetic disorder
Affects type 1 synthesis of collagen during ossification
Bones are brittle and prone to fractures
Legal importance - confusion with abuse


Describe rickets (children) and osteomalacia (adults)

Absence of vitamin D causes poorly minrealaised, pliable matrix to form(osteoid)
Unable to support bodyweight - bend and fracture (rickets)
Back and bone ache (osteomalacia)


Describe osteoporosis

Loss of bone matrix, structural density and demineralaisation
Increases risk of fractures
Easily detected by dexa bone density scan
Risk factors - age, menopause, gonad deficiency, lack of activity


Describe achondroplasia

Autosomal dominant point mutation in FGFQ3 gene
Results in gain of function of FGFQ3 gene which decreases endochondrial ossification, cellular hypertrophy and production of cartilage matrix & increases proliferationof chondrocytes
Results in short limbs, normal trunk


Describe effect if hormonal abnormalaties on bone

Affect bone development in years of growth
Lack of GH -> ephysial cartilage -> pituatary dwarfism
Excess GH -> gigantism, acromegaly
Lack of gonads -> osteoporosis


What lifestyle factor increases risk of osteomalacia?

Inadequate dietary intake of calcium, vitamin D and phosphate


What lifestyle factor increases risk of osteoporosis?

Lack of physical excercise


What lifestyle factor increases risk of rickets?

Inadequate vitamin D ( stay indoors too much)


Describe the radiological and histological changes in osteoporosis

Reduced bone density, increases risk of fractures
Collagen framework and deposited minerals broken down faster than formed
Osteoclast activity> osteoblast activity
Medullary canals in the centre of bone become enlarged and gaps develop in lamellae making the bone fragile


List common risk factors for osteoporosis

Middle age onwards - bone thinner and more porus
Post menopause - falling oestrogen (osteoclasts not inhibited)
Poor diet
Insufficient excercise