The adrenal glands are paired endocrine glands found on top of the kidneys. They are composed of an inner medulla and an outer cortex, which is in turn divided into three zones.
The adrenal medulla is the central part of the adrenal gland. The secretory cells of the medulla are known as chromaffin cells and they are responsible for producing adrenaline and noradrenaline.
The zona glomerulosa is the outermost layer of the adrenal cortex, and is responsible for secreting the mineralocorticoid hormones, such as aldosterone, which are important in regulating fluid balance.
The middle layer of the adrenal cortex is the zona fasciculata. It is the thickest of the three Zonas, measuring approximately 0.9mm and making up 50% of the mass of the Adrenal Gland. The cells of the zona fasciculata secrete the glucocorticoids cortisol and corticosterone, which regulate carbohydrate metabolism in the body.
The zona reticularis is the innermost layer of the adrenal cortex. It is responsible for production and secretion of androgens – these are responsible for the normal development of sexual characteristics during puberty.