Learning Objectives

• Differentiate between the right (pyramidal) and left (semilunar) adrenal glands.
• Master the three histological zones of the cortex and their specific hormones.
• Understand the triple arterial supply and the asymmetrical venous drainage.
• Identify the embryological origin of the medulla and its role in the “fight-or-flight” response.

Anatomical Location & Relations

The adrenal (suprarenal) glands are retroperitoneal organs sitting on the superomedial poles of the kidneys. They are enclosed by renal fascia, which attaches them to the diaphragm.

Internal Structure: Cortex vs. Medulla

The gland consists of two embryologically and functionally distinct parts:

The Adrenal Cortex (Mesoderm)

Divided into three zones (Mnemonic: G-F-R — “The deeper you go, the sweeter it gets”):

• Zona glomerulosa (Salt): Produces mineralocorticoids (e.g., aldosterone).
• Zona Fasciculata (Sugar): Produces Glucocorticoids (e.g., Cortisol).
• Zona Reticularis (Sex): Produces Androgens (e.g., DHEA).

The Adrenal Medulla (Neural Crest)

Contains chromaffin cells. These are essentially modified post-synaptic sympathetic neurons that secrete Catecholamines (Adrenaline and Noradrenaline) directly into the blood.

Vasculature & Drainage

The adrenal glands have one of the highest rates of blood flow per gram of tissue in the body.

Clinical Relevance: Pheochromocytoma

A Pheochromocytoma is a tumor of the chromaffin cells (usually in the medulla).

• Symptoms: The “classic triad” of episodic Palpitations, Headaches, and sweating (Diaphoresis) due to catecholamine excess.
• High-Yield Management: Patients must be treated with an alpha-blocker (like Phenoxybenzamine) before a beta-blocker to prevent a hypertensive crisis.

Activity