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Question Video: Describing the Functions of the Parathyroid Glands Biology

What is the primary function of the parathyroid hormone?


Video Transcript

What is the primary function of the parathyroid gland? (A) To regulate the basal metabolic rate of the body. (B) To regulate the calcium levels in the blood. (C) To control the rate of unconscious activities, for instance, heart rate and breathing rate. (D) To regulate body temperature. Or (E) to stimulate the uptake of glucose by the liver.

This question asks about the parathyroid glands. To answer this question correctly, let’s review the key facts about the structure and function of these pea-sized glands.

The parathyroid glands are endocrine glands. An endocrine gland is an organ consisting of a group of specialized cells that secrete hormones directly into the blood. The hormones, for example, insulin, are chemical messengers which are carried around the body to their target cells, where they bring about a response, for example, the uptake of glucose by the liver cells.

The parathyroid glands are two pairs of small, oval glands about the size of peas, which lie next to the thyroid gland in the neck and work closely with it. To see how they all work together, let’s start with the thyroid gland.

If you look at this diagram of the cells making up the thyroid gland, you can see there are two types of secretory cells: follicular cells and parafollicular cells. The follicular cells secrete the thyroid hormones thyroxine and triiodothyronine. The main function of these is to regulate the basal metabolic rate of the body, but they also help maintain healthy skin and hair.

Calcitonin is secreted by the parafollicular cells, also known as C cells as they secrete calcitonin. Calcitonin decreases calcium levels in the blood by preventing release from the bones to maintain a normal, healthy calcium concentration.

Now let’s look at the parathyroid glands. The parathyroid glands secrete parathyroid hormone. This hormone works together with calcitonin to maintain calcium homeostasis in the body. When the calcium levels in the blood are low, parathyroid hormone stimulates the breakdown of bones to release calcium into the bloodstream.

Calcium is the main mineral in the bones making them dense and strong. However, calcium ions are also very important in blood clotting, muscle contraction, and the transmission of signals in the nervous system. So levels in the blood need to be controlled carefully.

Calcitonin and parathyroid hormone control the levels of calcium in the blood by negative feedback as shown in this diagram. As levels of calcium rise in the blood, calcitonin is released and returns them to the normal level. When calcium levels drop, parathyroid hormone is released to raise the levels back up to the norm.

Now that we have reviewed how the thyroid gland and parathyroid gland work together, we can return to our question. We now know that the correct answer to the question is (B). The primary function of the parathyroid gland is to regulate the calcium levels in the blood.

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