Henry Gray (18251861). Anatomy of the Human Body. 1918.
on an average about 6 mm. in length, and from 3 to 4 mm. in breadth, and usually present the appearance of flattened oval disks. They are divided, according to their situation, into superior and inferior. The superior, usually two in number, are the more constant in position, and are situated, one on either side, at the level of the lower border of the cricoid cartilage, behind the junction of the pharynx and esophagus. The inferior, also usually two in number, may be applied to the lower edge of the lateral lobes, or placed at some little distance below the thyroid gland, or found in relation to one of the inferior thyroid veins.1
In man, they number four as a rule; fewer than four were found in less than 1 per cent. of over a thousand persons (Pepere2), but more than four in over 33 per cent. of 122 bodies examined by Civalleri. In addition, numerous minute islands of parathyroid tissue may be found scattered in the connective tissue and fat of the neck around the parathyroid glands proper, and quite distinct from them.
Development.The parathyroid bodies are developed as outgrowths from the third and fourth branchial pouches (Figs. 1175).
A pair of diverticula arise from the fifth branchial pouch and form what are termed the ultimo-branchial bodies(Fig. 1175): these fuse with the thyroid gland, but probably contribute no true thyroid tissue.
Note 1. Consult an article Concerning the Parathyroid Glands, by D. A. Welsh, Journal of Anatomy and Physiology, vol. xxxii. [back]
Note 2. Consult Le Ghiandole paratiroidee, by A. Pepere, Turin, 1906. [back]