The adrenals - hormone factory in the pocket size

Did you know that the adrenal glands are called that because they are next to the kidneys? Otherwise, both organs have little to do with each other: the kidneys produce our urine and regulate blood pressure and acid-base balance; The adrenal glands produce hormones.

What do the adrenal glands look like and where do they lie exactly?

The Latin name of the adrenal gland, Glandula suprarenalis, literally means "gland above the kidney". In humans, the two adrenals sit like small caps on top of the kidneys. They each weigh about five to ten grams and are about the size of two matchboxes. Together with the kidneys, they are embedded in a fat capsule (Capsula adiposa renis) and connective tissue (Fascis renis).

The adrenal glands consist of bark (cortex glandulae suprarenalis) and medulla (medulla glandulae suprarenalis) that perform various tasks. The adrenal cortex accounts for about four-fifths of the total weight of the adrenal glands and can be divided into three layers according to their appearance:

  • On the far side is the glomerular zona, in which the individual cells are arranged in piles.
  • This is followed by the zona fasciculata, in which the cells form strands or parallel bundles.
  • The innermost layer, zona reticularis, is built up like a net.

The adrenal cortex encloses the adrenal medulla (medulla glandulae suprarenalis). The marrow belongs to the sympathetic nervous system and contains hormone-producing cells as well as nerve cells.

What functions do the adrenal glands have?

The Roman anatomist Bartholomeus Eustachius discovered and named the adrenals as early as 1564, but it was not until more than three centuries later that all their functions were known: the four different zones of the adrenals specialize in the production of different hormones.

Multi-talented adrenal cortex

The adrenal cortex alone produces over 40 different hormones. The three most important are aldosterone, cortisol and the androgens. The adrenal cortex is controlled via hormonal control circuits, above all via the hypothalamus and pituitary gland in the brain.

At the very outside, in the glomerular zona, the cholesterol component is converted to aldosterone. This mineral corticoid, together with the renin-angiotensin system, regulates the sodium and potassium content of our body and is important for the fluid and salt balance. Aldosterone causes the kidneys to retain more sodium and thus retain water. As a result, it affects blood pressure (in simple terms: the more water and sodium in the body, the higher the blood pressure).

The zona fasciculata produces glucocorticoids like the versatile cortisol: it increases the formation of new sugars, breaks down fats and proteins. This gives the body more energy. In addition, cortisol inhibits inflammation because it suppresses immune system reactions. Cortisol is closely related to cortisone, which is used for example in allergic or inflammatory reactions as a drug.

From the zona reticularis come the androgens. In the body androgens are converted into the sex hormone testosterone, which promotes the function and growth of penis and testicles in man and regulates the production of sperm. Unlike aldosterone and cortisol, however, only five percent of androgens are produced in the adrenal cortex, the rest produce the testes.

Stress organ adrenal medulla

The adrenal medulla is part of the sympathetic nervous system. Here, the catecholamines epinephrine (= epinephrine), norepinephrine (= norepinephrine) and dopamine are produced from the amino acid L-tyrosine. Catecholamines are also called stress hormones because they are active in the body, especially in stress situations: blood pressure and heart rate rise, blood sugar levels and sweat secretion are increased, the bowel movement is slowed down and the airways are widened. This is useful in an attack by wild animals or mugger, in everyday life, for example, before an exam or a speech, rather counterproductive.

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