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How do the kidneys work?

The kidneys are the body's sewage treatment plants: they produce urine and thus excrete waste materials such as urea, which are produced in the body or ingested through food. Urea is produced when proteins are broken down. The body can also dispose of medicines, drugs or poisons in the urine.

In addition to producing urine, the kidneys have other important tasks: They regulate the fluid balance by either retaining water or excreting more with the urine. When they hold back water, more fluid gets into the blood vessels. This increases the amount of blood and increases blood pressure. When the kidneys excrete more water, the amount of blood and blood pressure decreases. In addition, certain cells in the kidneys produce the protein renin. It has a hormone-like effect that increases blood pressure.

In addition, the kidneys produce the two important erythropoietin and calcitriol. Erythropoietin promotes the formation of red blood cells. Calcitriol is the active form of vitamin D and, among other things, regulates the amount of calcium in the body.

The kidneys also keep the so-called acid-base balance in balance. So they ensure that the blood does not become too acidic or too basic. The energy metabolism is also influenced by the kidneys: If there is too little sugar () in the blood, the kidneys can produce sugar itself and release it into the blood.

On each kidney there is a pyramidal gland - like a little cap -: the adrenal gland. The adrenal glands make various vital ones, including cortisol.