Final answer:
The parathyroid contains chiefly chief cells, which produce the parathyroid hormone (PTH) to regulate blood calcium levels, and oxyphil cells of unclear function. PTH increases blood calcium levels by affecting the kidneys, bones, and absorption in the digestive system. PTH and calcitonin have opposing effects on calcium homeostasis and cAMP levels.
Step-by-step explanation:
Cell Types and Functions in the Parathyroid
The parathyroid glands include two types of cells: chief cells and oxyphil cells. The chief cells are responsible for the production of parathyroid hormone (PTH), which plays a critical role in regulating blood calcium levels by (1) enhancing calcium reabsorption by the kidneys, (2) stimulating osteoclast activity while inhibiting osteoblast activity in the bones, and (3) stimulating the synthesis and secretion of calcitriol, which enhances digestive system's ability to absorb calcium. Oxyphil cells exist in the parathyroid, but their function remains less understood. The effect of PTH on cAMP levels is that it generally leads to an increase, which is instrumental in the hormone's action mechanism.
PTH and calcitonin typically work in opposition to maintain homeostatic calcium levels. Whereas PTH increases blood calcium concentrations when they fall below normal, calcitonin, produced by the thyroid gland, acts to lower blood calcium levels when they are high.