Final answer:
The parathyroid glands produce parathyroid hormone (PTH) to regulate blood calcium levels by increasing both the release of calcium from bones into the bloodstream and its reabsorption in the kidneys, as well as enhancing dietary calcium absorption.
Step-by-step explanation:
The parathyroid gland is an essential component of the endocrine system, located behind the thyroid gland in the neck. Each person typically has four of these glands, but the number can vary from two to six. The primary role of the parathyroid glands is the regulation of blood calcium levels through the secretion of parathyroid hormone (PTH).
PTH works by (1) enhancing calcium reabsorption in the kidneys, (2) stimulating osteoclast activity and inhibiting osteoblast activity in the bones, which mobilizes calcium into the bloodstream, and (3) stimulating the synthesis and secretion of calcitriol by the kidneys to enhance dietary calcium absorption.
These processes help maintain calcium concentration in the blood within a narrow, healthy range, which is critical for various body functions including bone health, muscle contraction, and nerve function.