Final answer:
The thyroid gland, located in the neck, consists of follicles producing thyroid hormones and parafollicular cells producing calcitonin. It is regulated by TSH from the pituitary and is closely associated with the parathyroid glands producing PTH for calcium homeostasis.
Step-by-step explanation:
The thyroid gland is a crucial part of the endocrine system and is located in the front of the neck, below the larynx. It is made up of two main parts: the follicles and the parafollicular cells. The follicles are responsible for the production and storage of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), which are vital in regulating the body's metabolic rate. These hormones are synthesized using iodine absorbed by the follicles. The parafollicular cells, also known as C cells, produce the hormone calcitonin, which helps regulate calcium levels in the blood.
The thyroid's function is regulated by the thyroid-stimulating hormone (TSH) released by the pituitary gland. The parathyroid glands, which are located on the posterior surface of the thyroid gland, produce parathyroid hormone (PTH). This hormone plays a critical role in calcium homeostasis along with calcitonin.