The<unk>  is the outer region and also the largest part of an<unk>  gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is also a secondary site of androgen synthesis. Layers The<unk>  comprises three main zones, or layers that are regulated by distinct hormones as noted below. This anatomic zonation can be appreciated at the microscopic level, where each zone can be recognized and distinguished from one another based on structural and anatomic characteristics. ;Zona glomerulosa :The outermost layer, the zona glomerulosa is the main site for the production of aldosterone, a mineralocorticoid. The synthesis and secretion of aldosterone are mainly regulated by the renin–angiotensin–aldosterone system. The zona glomerulosa cells express a specific enzyme aldosterone synthase (also known as CYP11B2). Aldosterone is largely responsible for the long-term regulation of blood pressure. Aldosterone's effects are on the distal convoluted tubule and collecting duct of the kidney where it causes increased reabsorption of sodium and increased excretion of both potassium (by principal cells) and hydrogen ions (by intercalated cells of the collecting duct). Sodium retention is also a response of the distal colon, and sweat glands to aldosterone receptor stimulation. Although sustained production of aldosterone requires persistent calcium entry through low-voltage<unk> tivated Ca2+ channels, isolated zona glomerulosa cells are considered nonexcitable, with recorded membrane voltages that are too hyperpolarized to permit Ca2+ channels entry. :The secretion of aldosterone is also stimulated by adrenocorticotropic hormone <unk> TH). :The expression of neuron-specific proteins in the zona glomerulosa cells of human adrenocortical tissues has been predicted and reported by several authors and it was suggested that the expression of proteins like the neuronal cell adhesion molecule (NCAM) in the cells of the zona glomerulosa reflects the regenerative feature of these cells, which would lose NCAM immunoreactivity after moving to the zona fasciculata. However, together with other data on neuroendocrine properties of zona glomerulosa cells, NCAM expression may reflect a neuroendocrine differentiation of these cells. ;Zona fasciculata :Situated between the glomerulosa and reticularis, the cells of the zona fasciculata synthesize and secrete glucocorticoids, such as 11-deoxycorticosterone, corticosterone, and cortisol in humans. The major hormone that stimulates cortisol secretion in humans is the<unk> TH that is released from the anterior pituitary. It has been shown that the steroidogenic capacity of the zona fasciculata increases during illness in infants. ;Zona reticularis :The inner most cortical layer, the zona reticularis produces androgens, mainly dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), and androstenedione (the precursor to testosterone) in humans. The secretion of DHEAS is also stimulated by<unk> TH.
Adrenal cortex
Adrenal gland
Pituitary gland
Kidney
Areolar gland
Liver
Allothalamus
Serous gland