The adrenal glands are paired structures that lie on top of each kidney. This places them in a retroperitoneal position in the body. Just like the kidneys, the adrenal glands lie outside the peritoneum and near the body wall in close contact with the spine and supporting muscles. The adrenal glands are actually two glands in one. The outside, or adrenal cortex, is part of the endocrine system and secretes steroid-type hormones. The inner cells, the adrenal medulla, are often discussed in anatomy texts as part of the central nervous system even though they secrete hormonal-type chemicals.

The adrenal medulla, or inner core of the gland, is actually made up of highly modified nervous cells (cromaffin cells) that are part of the sympathetic, or autonomic nervous system. The cells are rounded, but slightly columnar and tightly packed. They originate from ectodermal cells. As a unit they...