The adrenal gland, or, as it was known more frequently in past years, the suprarenal gland, is unusual in that it consists of two parts which are virtually unrelated from the viewpoints of origin, histologic structure, and function. In lower vertebrates these parts are separate, in somewhat higher forms of life they are closely associated, and in mammals they are united to form a single structure.37 The adrenal medulla with which we are concerned at this time develops from the ectoderm and has a common site of origin with cells that form the sympathetic ganglia. In contrast, the cortex is of mesodermal origin, arising from the coelomic epithelium. There are probably few structures, excluding those of the nervous system, which for their size play a more important role in health and disease than the adrenal glands.
The embryonic cells which subsequently give rise to the adrenal medulla have been
PRIESTLEY JT, KVALE WF, GIFFORD RW. PheochromocytomaClinical Aspects and Surgical Treatment. Arch Surg. 1963;86(5):778-790. doi:10.1001/archsurg.1963.01310110088013