Question

how is calcium homeostasis using all the systems relevant to its regulation?

Answer 1

Calcium homeostasis is controlled by PTH, vitamin D, and calcitonin and the interactions of the skeletal, endocrine, digestive, and urinary systems.

When blood calcium levels are low, the parathyroid hormone (PTH), secreted by the parathyroid glands is released, while calcitonin secretion is inhibited. PTH increases blood calcium levels by stimulating osteoclasts, which break down bone to release calcium into the blood stream, in addition to this it inhibits osteoblasts cell, which deposits bone, reduction calcium deposition in bone. In the kidneys , PTH increases blood calcium levels by increasing the amount of calcium resorbed by the kidneys before it can be excreted in the urine. In the intestine PTH acts by increasing dietary calcium absorption, PTH triggers the formation of calcitriol, which increases absorption of dietary calcium through the intestines.

On the other hand if blood concentration of calcium increases, PTH release is inhibited and parafollicular cells of thyroid gland increases calcitonin secretion in blood, the resulting high level of calcitonin in blood stimulates the bone to remove calcium from blood plasma and deposit it as bone.