Final answer:
The four small dime size glands behind the Thyroid Gland are the Parathyroid Glands, which secrete parathyroid hormone essential for calcium regulation in the body.
Step-by-step explanation:
The four small dime size glands that lie directly upon and behind the Thyroid Gland are the Parathyroid Glands. They secrete parathyroid hormone (PTH) that is responsible for regulating body calcium usage. Therefore, the correct answer is d) Parathyroid.
The parathyroid glands are crucial for maintaining balanced blood calcium levels. They release PTH when blood calcium levels are low, which stimulates bone cells to release calcium into the bloodstream. This process is essential for various physiological functions, including neuromuscular activities. Conversely, high blood calcium levels will inhibit the secretion of PTH, helping to maintain the equilibrium of calcium in the body.
Most people have four parathyroid glands, located on the posterior surface of the thyroid gland; however, the number can vary from two to six. These glands are embedded in the thyroid tissue and play a key role in calcium homeostasis by producing PTH.