Postnatal bone growth

Postnatal bone growth - calcification of bone matrix to...

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Postnatal bone growth: - longitudinal growth (growth in bone length) - appositional growth (growth in bone width) - regulated by growth hormone, which is regulated by thyroid hormones; later regulated by steroid hormones Bone Remodeling: Bone deposit: for bone growth, or to replace injured bone - osteoid seam of bone matrix is slowly calcified (calcification front forms) .. hydroxyapatite Bone resorption: for bone remodeling - osteoclasts (giant multinucleate cells from same stem cells that differentiate into macrophages) secrete lysosomal enzymes to digest organic matrix & acids to release calcium into solution Control of Remodeling: Hormonal control: - parathyroid hormone (PTH, from parathyroid gland): stimulates osteoclasts to resorb bone to raise blood calcium levels
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Unformatted text preview: calcification of bone matrix to lower blood calcium levels Mechanical stress:- Wolff's law: a bone remodels or grows in response to the forces placed on it- Bones are generally thickest at sites with greatest stress Repair of fractures: Fracture types:- displaced (ends out of alignment) & nondisplaced fractures- complete (bone broken through) & incomplete fractures- linear (along axis) & transverse (perpendicular to axis) fractures- open ( compound , breaks skin) & closed ( simple ) fractures Reduction: realignment of broken bone ends- closed reduction: bones coaxed into position by physician (or someone)- open reduction: bone ends are secured together by pins or wires- hematoma (mass of clotted blood) formation- fibrocartilagenous callus formation- bony callus formation- bone remodeling Osteomalacia: bones are inadequately mineralized (osteoid not calcified)...
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Postnatal bone growth - calcification of bone matrix to...

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