Parathyroid glands in reptiles.

Abstract

The parathyroid glands in reptiles generally develop from the third and fourth pharyngeal pouches. In lizards and crocodiles, usually only one pair of glands (from the third pouch) persists, while turtles and snakes generally retain both pairs of glands in adults. The glands consist of cell cords and are similar in structure to those of birds and mammals. A common feature of reptilian parathyroids is the organization of cells around a lumen in a follicular arrangement. The few physiological studies which have been made indicate that parathyroid function in reptiles is in many respects similar to that of mammals. For example, in lizards, parathyroidectomy results in tetanic convulsions and lowered values of plasma calcium, while administration of parathyroid extract increases mine phosphate and serum calcium in turtles, and increases the number of osteoclasts in bone of lizards and turtles. However, there are some obvious differences between parathyroid function in reptiles and mammals, on which much more work is needed.