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Adrenal Glands

The adrenal glands, or suprarenal glands, are two small glands; one is situated on top of each kidney. Each gland consists of two parts: an outer portion, the adrenal cotex, and an inner portion, and adrenal medulla. The cortex and the medulla are two glands in one, each secreting its own different endocrine hormones. The cortex secretes steroid hormones, or corticosteroids (complex chamicals derived from cholesterol), and the medulla secretes catecholamines (chemicals derived from amino acids).

Function of Adrenal Gland

The adrenal cortex secretes three types of corticosteroids.

Glucocorticoids

These steroid hormones have an important influence on the metabolism of sugars, fats, and proteins within the body cells and have a powerful anti-inflammatory effect.

Cortisol

Also called hydrocortisone), it is the most important glucocorticoid hormone. Cortisol increases the ability of cells to make new sugars out of fats and proteins (gluconeogenesis) and regulates the quantity of sugars, fats, and proteins in the blood and cells.

Cortisone

This is a hormone very similar to cortisol and can be prepared synthetically. Cortisone is useful in treating inflammatory conditions such as rheumatoid arthritis.

Mineralocorticoids

These hormones are essential to life because they regulate the amounts of mineral salts (also called electrolytes) that are retained in the body. A proper balance of water and salts in the blood and tissues is essential to the normal functioning of the body.



Aldosterone

is a mineralocorticoid hormone. The secretion of aldosterone by the adrenal cortex increases the reabsorption into the bloodstream of sodium (a mineral electrolyte commonly found in salts) by the kidney tubules. At the same time, aldosterone stimulates the excretion of another electrolyte called potassium. The secretion of aldosterone increases manyfold in the face of a severely sodium-restricted diet, thereby enabling the body to hold needed salt in the bloodstream.

Gonadocorticoids

These are sex hormones, androgen (male hormone) and estrogen (female hormone), that influence secondary sex characteristics, such as pubic and axillary hair in both boys and girls. Excess adrenal androgen secretion in females leads to virilism (development of male characteristics).

 

The adrenal medulla secretes two types of catecholamine hormonea:

Epinephrine (adrenaline)

This hormone increases cardiac rate, dilates bronchial tubes, and stimulates the production of glucose from a storage substance called glycogen when glucose is needed by the body.

Norepinephrine (noradrenaline)

This hormone constricts vessels and raises blood pressure.

Both epinephrine and norepinephrine are sympathomimetic agents because they mimic, or copy, the actions of the symathetic nervous system. During times of stress, these hormones are secreted by the adrenal medulla in response to nervous stimulation. They help the body respond to crisis situations by raising blood pressure, increasing heartbeat and respiration, and bringing sugar out of storage in the cells.





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