Also known as the suprarenal gland, it is a gland that is located above each kidney. It consists of an outer wall (cortex) that produces steroid hormones and an inner section (medulla) that produces other important hormones, such as adrenaline and noradrenaline.
The Italian anatomist Bartolomeo Eustachi discovered the suprarenal glands in 1563. He wrote about their shape and situation in a chapter dedicated to them in his publication though he offered no explanation to their function. Here is a photograph of human kidneys and their respective suprarenal glands separated (they are found right on top of the kidneys):
- https://archive.org/details/BIUSante_05548x01/mode/2up, pages 39-40.