The cortex usually envelopes the medulla completely. The adrenal cortex is divided into three areas.
1. zona glomerulosa,
2. zona fasciculata,
3. zona reticularis.
They have large amounts of smooth endoplasmic reticulum on electron microscopy.
The zona glomerulosa consists of flattened polyhedral cells. It is not well developed in man. It produces mineralocorticoids, e.g. aldosterone – which regulates the electrolyte levels in the blood.
Zona fasciculata produces glucocorticoids – e.g. cortisone which is responsible for carbohydrate metabolism.
Zona reticularis produces sex hormones which include androgens androgens, progesterone and estrogen.
The adrenal medulla belongs to the chromaffin tissue system and its cells undergo the so called positive chromaffin reaction. The cells are called phaeochromocytes or chromaffin cells. Chromaffin reaction involves the oxidation of norepinephrine by chromic salts e.g. potassium dichromate. The chromaffin reaction also involves the conversion of epinephrine to norepinephrine which then reacts with potassium dichromate to stain the cells brownish.
Phaeochromocytes (or chromaffin cells) are divided into the following:
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NA cells are cells that produce norepinephrine
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A cells are cells that produce epinephrine
Based on certain staining reaction, four types of NA cells have been described. These cells are also believed to produce peptides probably of the enkephalin series.
Under the electron microscope the cells have numerous rough endoplasmic reticulum and Golgi complexes. It also has many secretory granules.
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