The prestige of the nephron

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For each of the many responsibilities in the kidney special work area. Production process is started in the glomeruli, educated finest ramifications of capillaries. Clew covered as a bowl, a capsule. The vessel in which the blood to him was flowing, two times thicker than the one on which it flows away. Not surprisingly, part of the plasma is squeezed out of the capillaries, the benefit of their walls is permeable to water and substances with a low molecular weight. It sodium, potassium, chlorides, phosphates, glucose, parts of residual nitrogen, alien proteins.
Chemical composition, pH, conductivity filtered fluid differs little from the plasma. With one exception: through the capillary walls are not a fat-like substance and passed negligible its proteins. However, under the influence of adverse processes pores can grow, and then in the capsule gets an unexpected amount of protein. This is already the extraordinary phenomenon that finds the simplest analysis in the laboratory of the district polyclinic. But what we pass on to the analysis, nothing like liquid, wiatow of glomeruli in the capsule.
In a moment through the vessels of the kidney is about 1200 milliliters of blood, half of its plasma. Filtering surface reaches in both kidneys nearly 50 square meters. And the fifth part of the plasma filter: 120 ml per minute, more than 7 litres per hour, 150-200 liters per day. The figures, of course, medium, estimated, for the intensity of the filtration process varies according to the time of day, the needs of the body, other circumstances. But no matter how rough figures, it is clear that they are absolutely not comparable with the amount of fluid that the kidney during the day is removed from the body. The difference is returning back into the liquid medium of the organism.
Otherwise also cannot be. Otherwise, we would have to satisfy thirst almost tanks. We quietly cost one and a half liters and owe it to the renal tubules.
Each ball leaves its such tubule. It flowing filtered fluid. But tubule is not passive transport highway. On its shores filtered part of plasma subjected to vigorous treatment. The glomerulus and tubule are the main functional, the production unit of the kidney nephron. Its length is 5 centimeters. Here are biophysical, biochemical processes through which the kidney cope with all of its responsible diverse tasks.
Hard work is humming at the beginning of the tubule. His cell suck and pass into the blood lion's share of the water and the valuable substances introduced into the nephron. Experiments on mice, Guinea pigs showed that in this area in the blood is returned to 80 percent of the filtrate. So, here is captured 80 percent of the sodium, the preservation of which the kidneys particularly care: 99 percent of it they give in the blood. Just as vigorously, almost completely saved from squandering the second most important electrolyte - potassium and his brethren, and also a large part of bicarbonate, these workaholics buffer systems, and other valuables. This nephron consumes a lot of energy, but the game, as they say, is worth the candle.
For sodium according to the laws of osmotic fond of equality in the blood of the water in the huge volumes if to compare them with the size of the kidney. Because it is small: 12-15 cm long, 7-8 in the width and thickness of 4-5 cm. Every minute about 100 milliliters of water goes from the start of the departments of nephrons back into the blood. Further embark on a voyage 17-20 milliliters.