Anatomy of the Adrenal Gland

Adrenal glands are triangle shaped and located on the top of each kidney. CT scan demonstrating the right and left normal adrenal glands (arrows).

Where are Adrenal Glands Located?

Adrenal glands are orange-colored glands located on the top of both kidneys. Adrenal glands are about the size of a fortune cookie and are triangular shaped, sitting on top of the kidneys like hats. Everyone has two adrenal glands that make several important hormones required for healthy life. Although some adrenal conditions are treated with medication, most hormone-producing adrenal tumors are treated with surgery to remove the adrenal gland, or only the adrenal tumor, that is causing a very specific hormone problem. What the hormones do is explained on our page about adrenal gland function.

The Right Adrenal Gland: The adrenal gland on the right side is located on top of the right kidney and is very close to the inferior vena cava (IVC). The IVC is the biggest vein in the body and brings blood back to the heart from the lower half of the body. The right adrenal gland is also very close to the liver. The kidney, IVC and liver are very important structures and it is crucial that the adrenal surgeon is experienced in dealing with them. These structures lie only millimeters from the gland, which is why experience matters.

The Left Adrenal Gland: The left adrenal gland is located on top of the left kidney. It is very close to the splenic artery, which is the major artery that goes to the spleen, and the tail of the pancreas. The pancreas is a very sensitive organ that, when irritated or injured, can cause serious complications such as pancreatitis. Thus, once again it is important that surgery in this area is performed very gently by an experienced surgeon.

The outer adrenal cortex produces different hormones than the inner adrenal medulla. FIGURE: A normal adrenal gland demonstrating the adrenal medulla (inner layer), and the adrenal cortex (outer layer). The adrenal glands are shaped like a triangular fortune cookie. And they really are orange in color!

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Differences Between the Adrenal Medulla and the Adrenal Cortex

The adrenal medulla and cortex have completely different functions and produce very different hormones. In fact, when fetuses are only a few weeks old, the adrenal glands form from two different cell types and two different embryonic areas.

Inside the Adrenal Gland: The Medulla and Cortex. The adrenal glands are paired (you have two of them) flat glands with a triangular shape, each weighing about 4 to 5 grams (about the weight of a nickel). When we cut the adrenal gland in half, we can see with our eyes two distinct regions that are different shades of orange. These two major sections of the adrenal are called the adrenal medulla (inner layer), and the adrenal cortex (outer layer).

The Adrenal Medulla: The adrenal medulla comes from the neural crest (i.e. embryological basis similar to your central and peripheral nervous systems). It contains homogenous sheets of cells organized into nests. Cells have large varied nuclei and abundant cytoplasm packed with numerous secretory granules containing catecholamines (the fight-or-flight hormones adrenaline and noradrenaline) and other substances specific to chromaffin cells. Tumors of the medulla are called pheochromocytomas.

The Adrenal Cortex: The adrenal cortex is of mesodermal origin and is derived from the adrenogenital ridge (sorry for the technical detail). The adrenal cortex is organized into three layers, each with a different function:

Transection of a portion of normal adrenal tissue displaying the adrenal cortex (yellow), medulla (brownish), and surrounding fat.

• The most superficial layer is the zona glomerulosa, responsible for aldosterone production. Too much aldosterone causes primary aldosteronism (Conn's syndrome).
• The middle zone is the zona fasciculata, containing radial columns of lipid-laden (fat-filled) cells that store cholesterol for steroidogenesis (the making of steroids) and primarily produce cortisol. Too much cortisol from the adrenal is called adrenal hypercortisolism (AHC).
• The inner layer, the zona reticularis, makes androgen precursors (weak male-type sex hormones) such as DHEA and DHEA-S.

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Blood Supply to the Adrenal Glands: Adrenal Arteries and the Adrenal Vein

Dissection of the inferior vena cava (IVC), normal adrenal cortex, and the adrenal tumor during a right Mini Back Scope Adrenalectomy (MBSA). The blood supply to the adrenal is threefold: via the superior adrenal arteries from the inferior phrenic arteries, the middle adrenal from the aorta, and the inferior adrenal artery from the renal arteries. Blood passes from the outer cortex to the inner medulla, and the gland is drained in most cases by a single central vein which empties its blood into the vena cava on the right and the renal vein on the left. The right adrenal vein is short and enters the vena cava directly, which is one reason adrenal vein sampling (AVS) is technically difficult.

Adrenal surgery is discussed on other pages of this website, but now that you know about the anatomy of the adrenal gland you understand why adrenal surgery is tricky and should be done by a surgeon who performs adrenal operations regularly. The adrenal glands lie toward the back of the body, behind the liver, spleen, pancreas and bowel. This is why we prefer to reach them through the back with the Mini Back Scope Adrenalectomy (MBSA), which avoids working around those organs. The typical surgeon who performs adrenal surgery does about one adrenal operation per year; if your surgeon performs only a few, you may want to find a surgeon with much more experience. Outcomes are directly related to the experience of the surgeon and how many adrenal operations he or she performs. About half of our patients come from outside Florida, including from around the world.

Last updated October 2026.