Learning Objectives
- Identify the three distinct histological layers of the adrenal cortex.
- Distinguish between the outer capsule and the inner medulla.
- Memorize the hormonal products associated with each zone.
- Understand the clinical organization of the gland during low-power microscopic examination.
Overview of Adrenal Histology
The adrenal gland is an essential endocrine organ. At low power, the gland is clearly divided into an outer cortex and an inner medulla, all enclosed by a protective capsule.
Characteristic Features: The Adrenal Cortex
The cortex is organized into three layers (from superficial to deep):
- Zona Glomerulosa: Located just beneath the capsule. These cells are arranged in rounded clusters and produce mineralocorticoids (e.g., Aldosterone).
- Zona Fasciculata: The thickest layer. Cells are arranged in long cords (fascicles) and produce glucocorticoids (e.g., Cortisol).
- Zona Reticularis: The innermost layer of the cortex. Cells form a branching network and produce androgens.
Adrenal Medulla
- Located at the center of the gland.
- Composed of chromaffin cells, which are derived from neural crest cells.
- Produces catecholamines (Epinephrine and Norepinephrine) in response to sympathetic stimulation.
Clinical Relevance: Glandular Function
- Adrenal Insufficiency: Damage to the cortex (such as in Addison’s disease) leads to a deficiency in cortisol and aldosterone.
- Hyperplasia: Thickening of specific zones, like the zona fasciculata, can occur in response to excess ACTH, leading to Cushing’s Syndrome.
- Pheochromocytoma: A tumor arising from the chromaffin cells of the medulla, resulting in clinical symptoms of hypertension and palpitations due to excess adrenaline.
