How do the skeletal and endocrine systems interact in calcium regulation?

• A. The endocrine system increases blood flow to bones.
• B. The endocrine system releases hormones to regulate calcium absorption.
• C. The skeletal system eliminates excess hormones.
• D. The skeletal system produces hormones for calcium balance.

Answer: (B)

The endocrine system plays a crucial role in regulating calcium levels in the body through the release of specific hormones. One of the main hormones involved in calcium regulation is parathyroid hormone (PTH), which is secreted by the parathyroid glands when blood calcium levels are low. PTH acts on various organs, including the bones, kidneys, and intestines, to increase calcium levels in the bloodstream.

In the bones, PTH stimulates the activity of osteoclasts, which are cells that break down bone tissue, releasing calcium into the bloodstream. Additionally, PTH promotes the activation of vitamin D in the kidneys, which enhances calcium absorption in the intestines. Conversely, when blood calcium levels are high, the thyroid gland releases calcitonin, which helps to lower calcium levels by inhibiting osteoclast activity and promoting calcium deposition in bones.

This complex interplay demonstrates how the endocrine system, through hormone release, regulates calcium absorption and maintains calcium homeostasis, thereby ensuring that the skeletal system maintains its strength and function in the process.