Explain briefly the structure and functions of middle ear.
Calcitonin (from thyroid) : Essential for maintaining bone strength as it does not allow calcium mobilisation from bones. It also lowers plasma level of calcium ifthe same is high. Parathormone: Low level of parathormone secretion decreases blood plasma level of calcium, prevents reabsorption from bones and causes tetany. Higher levels of parathormone (PTH) increase plasma level of Ca2+ by withdrawal from bones resulting in (i) Inflammation and tenderness in bones due to dissolution of calcium from bones, formation of cavities which get plugged with fibrous nodes and cysts (osteitis fibrosa cystica) making bones soft deformed and prone to fracture, (ii) Excess plasma calcium gets deposited in various parts of body which often leads of obstruction and death.
