Myelinated nerve fibers in the parathyroid gland of the dog: a light and electron-microscopic study.

The distribution of myelinated and non-myelinated nerve fibers in the parathyroid glands of the dog was studied by light and electron microscopy. The mixed fasciculi with myelinated nerve fibers (average diameter 7.0 micron) and unmyelinated fibers were present independent of the adventitia of the arterioles. The mixed fasciculi were accompanied by large amounts of collagen fibrils running in the direction of the nerve fibers. The fasciculi were surrounded by a complete sleeve composed of a perineural epithelial sheath which a basal lamina on both sides. The possibility that these fibers might represent an afferent pathway is discussed.