Slide 2.1
An illustration of a 6-7 week embryonic pharynx and its derivatives. The parathyroid glands are derived from the third and fourth pharyngeal pouches, also called brachial clefts. The inferior parathyroid glands develop from the third pharyngeal pouch (together with thymus). The superior parathyroid glands develop from the fourth pharyngeal pouch.

Slide 2.2
Low power view of a normal parathyroid. The parathyroid cells (called chief cells) are arranged in cords and trabeculae and separated by adipose tissue. The chief cells produce the parathyroid hormone (PTH). The parathyroid gland has a rich capillary network in which PTH is directly released. PTH is regulated by serum level of free calcium.