Adrenal Gland

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Adrenal Gland

Introduction

The adrenal glands or suprarenal glands are two retroperitoneal structures of crescent shape situated on the right and left side in the human body, i.e. above the kidney. Its function is to regulate the responses to stress, through the synthesis of corticosteroids mainly cortisol and catecholamine's primarily adrenaline.

Anatomy

From the anatomical viewpoint, the adrenal glands are located in the retro peritoneum anterosuperior to the kidneys and are irrigated by the adrenal arteries. They consist of two different structures; which are the adrenal medulla and the adrenal cortex. Both structures are innervated by the autonomic nervous system (Kannan, 1988). As its name suggests, the adrenal medulla is located within the gland, surrounded by the adrenal cortex that forms the surface.

Adrenal Medulla

The adrenal medulla is mainly composed of chromaffin cells producing hormones; adrenal medulla is the main location in the body that converts tyrosine to catecholamines, epinephrine (also known as adrenaline) and norepinephrine. The cells derived from the adrenal medulla are logically the altered form or type of postganglionic neurons, and preganglionic autonomic nerve fibers which directly leads the cells to central nervous system (Kannan, 1988). As the synapses between postganglionic neurons and preganglionic fibers occur in autonomic ganglia, the adrenal medulla can be considered a nerve ganglion sympathetic nervous system. In response to a stressful situation for instance exercise or imminent danger the cells of the adrenal medulla produces catecholamine's that are incorporated into the blood, in a 70-30 ratio of epinephrine and norepinephrine respectively. Epinephrine produces significant effects as increased heart rate, vasodilation, bronchodilation and increased metabolism which are the fleeting responses.

Adrenal cortex

The adrenal cortex or adrenal gland is located surrounding the circumference of the adrenal gland. Its function is to regulate various metabolic components in the production of mineral corticoids and glucocorticoids that include aldosterone and cortisol. The adrenal cortex is also a secondary point for androgen synthesis (Blake & Boland, 2009). The adrenal outer cortex is secretes steroid hormones (lipid nature), so that their cells have abundant SER (smooth endoplasmic reticulum) and mitochondria. Based on the cell types and the function they perform, they are divided into three different layers of tissue:

Glomerulosa Zone - produces mineralocorticoid also known of aldosterone.

Fascicular Zone - produces about 95% of glucocorticoids, primarily cortisol.

Reticular Zone - produces androgens including testosterone

Zona glomerulosa

The zona glomerulosa cells of the adrenal cortex is its external layer which produces secretes mineralocorticoids such as aldosterone and desoxycorticosterone while acting on the kidney nephorns' as distal convoluted tubule to increase: potassium level in body; reabsorption of sodium and reabsorption of water via osmosis (Margioris & Chrousos, 2001). Zona glomerulosa while responding to the increase in level of potassium in body, angiotensinogenase or decrease in flow of blood towards kidney, as part of the renin-angiotensin system produces secrete the mineralocorticoid aldosterone into the blood.

Zona Fascicular

It is a layer present predominantly in the adrenal cortex, where cells are arranged in rows separated by partitions and cell capillaries. Zona fascicular are bulky and contain numerous granules giving its clear appearance of sponge ...