Final answer:
The Parathyroid Glands are responsible for regulating calcium levels in the body.
Step-by-step explanation:
The Parathyroid Glands are responsible for the regulation of calcium levels in the body. These glands are small structures located on the posterior surface of the thyroid gland. They produce Parathyroid Hormone (PTH), which increases blood calcium concentrations when calcium ion levels fall below normal. PTH enhances reabsorption of calcium by the kidneys, stimulates osteoclast activity and inhibits osteoblast activity in bones, and stimulates synthesis and secretion of calcitriol by the kidneys, which enhances calcium absorption by the digestive system.