Reabsorption

Partial or complete reabsorption of water, electrolytes and other dissolved substances into the blood in the tubular parts of the nephron from the primary urine formed by ultrafiltration of the blood in the renal corpuscles.

Recirculation: Chloride, bicarbonate, sodium, potassium and calcium ions (electrolytes) are reabsorbed into the blood or pumped back into the blood through active reabsorption - under ATP consumption. These electrolytes are passively followed by an inflow of water, so that already 2/3 of the primary urine is reabsorbed in the main part of the tubular system. Important: The reabsorption mechanism can only cope with a certain concentration, e.g. of glucose. If a threshold value is exceeded, the kidneys excrete the "excess" with the urine (diabetes).