Adrenal Gland Histology
- Two major divisions of the adrenal gland can be easily distinguished based on their H&E staining patterns. The adrenal cortex is a darker staining outer layer which encircles the entire gland whereas the adrenal medulla is the lighter staining inner region.
|Adrenal Cortex - Basic Components|
- Three layers of cells can be morphologically distinguished within the adrenal cortex itself. These layers correspond to zones functionally specialized to synthesize particular steroid hormones.
- Zona Glomerulosa: Outer Layer
- Cells of the Zona Glomerulosa are separated into small oval-shaped clusters by the fibrous capsule which invests the entire adrenal gland. These structures are reminiscent of glomeruli which gives this zone its namesake. Cells of this zone synthesize mineralocorticoids which were originally so named because they were shown to affect blood mineral levels. The physiologically most important mineralocorticoid is aldosterone.
- Zona Fasciculata: Middle Layer
- The Zona Fasciculata is the thickest layer and its cells are arranged in long cords or "Fascicula", giving this zone its namesake. Cells of this zone synthesizes Glucocorticoids which were originally so named because they were shown to affect blood glucose levels. Physiologically most important glucocorticoid is cortisol.
- Zona Reticularis: Inner Layer
- Cells of the Zona Reticularis are arranged in an inter-connecting network of cords giving the impression of a reticulum and thus the zone's namesake. Cells of this zone synthesizes "Adrenal Androgens": Named as such because they are androgens that are derived from the adrenal cortex and not from the gonads. The physiologically most important adrenal androgens are DHEA and androstenedione.
|Adrenal Medulla - Basic Components|
- The adrenal medulla is composed of a tightly packed arrangement of Chromaffin Cells which secrete norepinephrine and epinephrine directly into the circulation, thus known as circulating catecholamines.