Hyperparathyroidism causes hypercalcemia as a result of increased resorption of bone, reabsorption of calcium in the renal tubule, and absorption of calcium from the gut. PTH also decreases reabsorption of…
In severe hypercalcemia, precipitates can occur in the renal interstitium and incite an inflammatory reaction (nephrocalcinosis). By the time interstitial calcium deposits are visible on radiography, renal function is already…
Compared with other secretory systems, the parathyroid cell contains minimal amounts of hormone stored in the granules. Consequently, regulation of secretion occurs at the gene level and by cell proliferation….
The age-related subperiosteal expansion of long bones partially compensates mechanically for the endosteal resorption and resultant cortical thinning and increased porosity that occurs with aging. This radial outward displacement of…
The growth in width of a long bone is due primarily to subperiosteal formation of new bone, a process referred to as modeling, which begins before birth and continues even…
In addition, electricity can be induced in bone by means of an electric field with the electric apparatus remaining completely external to the limb; however, the amplitude and frequency of…
BONE ARCHITECTURE The architecture of the proximal femur beautifully illustrates the general principle that the external form and shape of bone as an organ and the internal organization of bone…
BIOELECTRIC POTENTIALS IN BONE Bioelectric potentials are measured from the surface of nonstressed bone (see Plate 2-38). In the intact tibia, the metaphyseal and epiphyseal regions are net electronegative, whereas…
One consequence of space flight is a significant loss of bone mass (both matrix and mineral) in a weightless environment. During the early Gemini and Apollo flights, x-ray densitometry studies…
Disuse osteoporosis may be focal, involving a single bone or limb (arthritis or limb immobilization), or it may be generalized (prolonged bed rest or paralysis). With generalized immobilization, bone loss…
