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Bone Growth lec 3 9/26/2012 7:08:00 AM Foetal bone growth: at birth 460 ossification centres  Foetus 10 weeks gestation 806 osification centres o Ribs+femur+tiny bits of hop bone,tibia,fibula,spine o Sphenoid is the only skull bone that is very ossfied  Foetus 18 weeks gestation : o Wrist =7 carpals none ossified at birth o Cartilaginous template for parts of skull+wrist+ankles o Takes 6 years for all to mineralize more time for final form  One carpel bone per year  Eventually 406 turn into 206 when all fusion has happened and finished Humans spend almost same time in gestation but more time in infancy  Human gestation stage is briefer in comparison to our lifespand o We have a shorter gestation t oget the baby out of the birth canal and be exposed to culture asap Endochocondral bone formation  Cartilage cells – chondrocytes – create template  Osteoblasts form bone o As soon as formed has to be remobed because child always growing  Osteoclasts remove bone  Osteocytes maintain bone : osteoblasts in next life stage  Blasts and clasts work together influenced by genes diet and environment : big topic Sex hormones: estrogens and androgens : stimulate bone formation  Post menopausal bone loss: estrogen removal so PTH is more active and PTH (parathyroid hormone) stimulate bone removal Babies:  Belly breathers: chest not fully formed  Needs to gain bone mass  Less fat  leaner Maxims  Growth is longest and strongest at the shoulder wrist and knee  From birth size increases allometrically o Skull +2, torso +3, arms+4, legs +5 1 o Each longbone has a specific trajectory of how it grows: one end (major growth end) grows longer and stronger o Bones hve to keep reshaping them selves to stay light: there has to be removal at the same time as the formation of bone: if it just grew would be too heavy to move around  Middle gets thinner , and ends at the ends  Coordinated effort between blasts and clasts Thick line is the median on the growth curve  Thin lines are centiles: 10 %,20% etc  First 36 months very fast trajectory of growth  Then slows down…until adolescent growth spurt (puberty)  Boys and girls very close at birth size+mid childhood o Boys go through puberty later about 2 years later then girls  Girls go through less of an adolescent growth spirt  Boys delay puberty but have a more intense one  Velocity curve o Plotting amout of gain of CM per year : speed at which a child is growing : highest velocity at fetal growth rate then goes stable at mid childhood and then puberty = spike in velocity  Must be based on longitudinal data because the shape will not work if you add boys and girls = merky  So we have to separate data Distance curves can be generated from past populations  Looks like they were growing fine until they died: abrupt death not illness because you would see illness in bone growth Body curve  Scammon curves  General curve: skeleton growth o Bone,brawn,blood,breathing,bowel and bladder,face: MOST o Neural curve: brain,eye and head dimensions:VAULT o Lymphoid incl. thymus  Biggest curve from birth to puberty because kids are out exploring then and need a strong immune system o Genital: primary sex organs and secondary sexual traits  100% refers to adult hood 2  what we are tracking is how different parts of the body reach that 100% @ adult hoo
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