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…

An intricate physiologic mechanism has evolved to prevent dangerous hypocalcemia: a reduction in calcium intake stimulates calcium absorption by the gastrointestinal tract, promotes renal calcium conservation, and stimulates net bone…

1. Calcium phosphate is minimally soluble in water. In fact, at the pH of body fluids and the concentrations of calcium and phosphate ions found in extracellular fluids, the critical…