Intro | Anterior Pituitary | Adrenal Glands | Ovaries | Pancreas | Posterior Pituitary | Testes | Thyroid
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The Adrenal Glands are located just above each of the kidneys. Each one is divided into the adrenal cortex (or outer layer) and the medulla (or inner layer). The Adrenal Cortex produces and secretes hormones that control salt and carbohydrate metabolism, and another that controls inflammatory reactions. The Adrenal Medulla produces and secretes hormones that are active during emotional arousal and sleep.
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The adrenal glands are named for their location near (above) the kidney. In humans the gland is the result of fusion of two separate organs; hence the adrenal cortex and the adrenal medulla. Each is quite distinct in anatomy and activity. The inner medulla is closely involved with the autonomic nervous system, whereas the outer cortex is more exclusively glandular.
The adrenal medulla is actually a glandular extension of the sympathetic division of the autonomic nervous system. When the sympathetic division is activated in response to stress or a threat, the medulla releases two substances, epinephrine, and norepinephrine, into the blood stream. Each one stimulates target organs in the same fashion, but epinephrine is removed from the blood supply more slowly and has a more prolonged effect. Among these effects are increased heart rate, constriction of blood vessels to increase blood pressure, and increased metabolic rate to produce more energy.
The adrenal cortex produces and secretes more than 30 different steroids in response to the release of adrenocorticotropic hormone (ACTH) by the anterior pituitary. All fall into one of three classes: glucorticoids, mineralcorticoids, and androgens. Each, however, is made from cholesterol; indeed cholesterol is not all bad! Glucocorticoids (such as cortisol) are responsible for the breakdown metabolism (anabolism) of carbohydrates, fats, and proteins. The overall effect is to increase the availability of sources of energy. Cortisol release varies across the 24 hour, day cycle with highest levels shortly after the bulk of our daily sleep (4-5 a.m. for most of us). Mineralcorticoids (such as aldosterone) prevent the loss of chloride and sodium ions in urine by reabsorption of these elements in the kidneys. Aldosterone has similar effects along the intestinal tract and on the salivary and sweat glands. Blood pressure and heart rate are maintained at life sustaining levels when the balance of minerals is optimal. Androgens have the same masculinizing effects as testosterone.