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Adrenal Glands

*Glandulae suprarenales*

For medical students2 min readUpdated 2026-10-10

Adrenal glands (glandulae suprarenales) are paired endocrine glands located in the retroperitoneal fat directly superior to the upper poles of the kidneys. They play a critical role in endocrine regulation by synthesizing essential hormones to control metabolism and the stress response.

LocalizationRetroperitoneal fat, superior to the renal poles
Average weight11–18 g in an adult
StructureDivided into cortex and medulla
EffectsRegulation of blood pressure and cardiac contraction

Topography and Gross Appearance

Both adrenal glands are securely embedded in adipose tissue and enclosed within the renal fascia. Despite being paired organs, they differ in shape and exact location:

Surfaces and Margins

Anatomically, each adrenal gland features three main surfaces:

  1. Anterior surface (facies anterior).
  2. Posterior surface (facies posterior).
  3. Renal surface (facies renalis), which faces directly toward the kidney.

Additionally, two margins are described: the superior margin (margo superior) and the medial margin (margo medialis). Special attention should be paid to the anteromedial surface, where the adrenal hilum (hilum) is located. A major blood vessel, the central suprarenal vein (v. suprarenalis), exits the organ through this structure.

Internal Structure: Capsule and Parenchyma

Externally, the organ is covered by a thin fibrous capsule containing smooth muscle fibers. Connective tissue septa extend inward from this capsule to form the structural framework.

The parenchyma of the gland is visually and functionally divided into two distinct layers:

1. Adrenal cortex (cortex) It constitutes the bulk of the organ, has a yellowish-brown color, and consists of three consecutive zones:

2. Adrenal medulla (medulla) Located in the very center, it has a deep brownish-red color. It consists of specialized chromaffin cells of epithelial origin. These cells secrete vital stress hormones—epinephrine and norepinephrine. Their release leads to increased arousal, enhanced myocardial contractility, elevated sympathetic nervous system tone, and consequently, increased blood pressure.

Mnemonic

The cortical zones from capsule to center can be remembered as «Salt, Sugar, Sex» (Zona Glomerulosa = salt/mineralocorticoids, Zona Fasciculata = sugar/glucocorticoids, Zona Reticularis = sex/androgens).

Frequently asked questions

Which arteries supply blood to the adrenal glands?

Blood supply to the adrenal glands derives from three main arterial sources:

  • Superior suprarenal artery (a. suprarenalis superior) — branches from the inferior phrenic artery and supplies the adrenal cortex.
  • Middle suprarenal artery (a. suprarenalis media) — a paired visceral branch of the abdominal aorta.
  • Inferior suprarenal artery (a. suprarenalis inferior) — branches from the renal artery.

These arteries form a triple blood supply and anastomose extensively within the gland.

Where do the right and left central suprarenal veins drain?

The central suprarenal vein (v. suprarenalis) exits through the hilum and has different drainage pathways on the right and left sides:

  • Right suprarenal vein (v. suprarenalis dextra) — drains directly into the inferior vena cava (v. cava inferior).
  • Left suprarenal vein (v. suprarenalis sinistra) — typically drains into the left renal vein (v. renalis sinistra).
Which nerve plexuses and fibers innervate the adrenal glands?

Innervation of the adrenal glands is provided by the suprarenal plexus (plexus suprarenalis), which accompanies the adrenal blood vessels. The celiac plexus (plexus celiac) lies near the glands, giving rise to secondary plexuses that accompany vessels and innervate the organs.

Which organs are in contact with the anterior surface of the right adrenal gland?

The anterior surface of the right adrenal gland contacts the liver.

  • Liver (hepar) — its bare area contacts the anterior surface of the right adrenal gland.

Additionally, medially, the right adrenal gland borders the inferior vena cava (v. cava inferior), which runs along its medial margin.

What is the anatomical difference between the right and left adrenal glands?

The right adrenal gland is triangular and sits higher, whereas the left adrenal gland is semilunar and partially contacts the medial border of the upper renal pole.

Where is the adrenal hilum located and what passes through it?

The hilum is located on the anteromedial surface of the organ. The central suprarenal vein (v. suprarenalis) exits through it.

What hormones are produced by the different zones of the adrenal cortex?

The zona glomerulosa synthesizes aldosterone (mineralocorticoids), the zona fasciculata synthesizes cortisol (glucocorticoids), and the zona reticularis synthesizes androgens (sex hormones).

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