The structure of the kidneys and their work

People have two kidneys arelocated at the top of the waist on either side of the spine. Each kidney includes over a million independent of microscopic pocetak - nephrons. Part of the nephron is first of all a wonderful element renal glomerulus. It blood capillaries closely entwine the wall of the renal tubules. The process of formation of urine is extremely interesting.
Initially attracted to millions of renal glomeruli the blood is filtered in them and all, except blood cells and proteins, goes into the lumen of the tubule. This will be the so-called primary urine. It moves along the troughs with a very complex structure, and gradually absorbed back. Now in the blood returning only water and useful substances. Waste products of metabolism back not absorbed. Selective absorption - amazing property renal tubular cells. From 200 litres primary urine that is filtered in the glomeruli per day, 198,5 liter absorbed back. Excreted only 1.5 liters, which, however, contains all the toxins found in 200 litres primary urine. The total length of the renal tubules is 120 km.
Formed in the kidneys urine flows through a long tube - the ureters and into the bladder, where periodically deleted. Circular muscle that closes the outlet of the bladder is called sfinktera and relaxes with corresponding orders from the brain.