General functions of kidney: maintaining constant the osmotic pressure of the organism, the relative concentration of different plasmatic components, the pH, the total isosmotic volume of liquid in the body, elimination of waste and producing hormones. Osmotic work. Anatomy of the nephron. Glomerular filtration by the proximal convoluted tubule. Forces determining the glomerular filtration and its auto regulation. Definition of clearance. Plasma clearance of inulin, para-aminohippuric acid and glucose. Mechanisms of the splay in the plot between mass of substance eliminated with urine in unit time and the plasmatic concentration of the substance. Clearance of the urea. Clearance changes of a substance versus its plasmatic concentration. Function of the proximal convoluted tubule, the Henle’s loop, the distal convoluted tubule and the collecting tubule. Cycle of urea and osmotic diuresis. pH regulation by kidney: mechanism of reabsorption of filtered bicarbonate, and excretion of titration acid and ammonium sulphate. Water balance of our organism. Measurement and calculation of fluid compartments of the organism. Donnan equilibrium between compartments with diffusible and not diffusible ions through a separating membrane, resulting in a different ions concentration between adjacent compartments and an electrical potential difference across the membrane. Derivation of the Nernst equation.