The Role of the Nephron

The Roles of the Nephron of the 120 ml of blood that is filtered by the kidneys each minute, only I ml (that's less than I%) turns into urine that will eventually leave the body (after approximately 300 - 400 mis of it accumulates to fill the bladder!) That leaves 119 ml of fluid called filtrate to be returned back to the blood stream. Good thing, otherwise you would have to micturate (pee, urinate) once every 3 minutes and drink 1 L of fluid every 10 minutes in order to maintain Homeostasis!!! The one million nephrons in each human kidney are amazingly efficient at selectively removing wastes from the blood while at the same time conserving water, salt ions, glucose and other needed materials. The nephrons accomplish this task in 3 main steps; these 3 steps are also called the 3 main roles of the nephron: Filtration, Reabsorption and Secretion.

Fiftratffln Filtration is aecomplished by the movement of fluids from the blood into the Bowman's capsule.

Beabsorpttort Reatuorptias wolves the selective transfer of essential solutes and water back into the blood. Secretion Secretion Involves the movement of wastes from the blood into the mphron.

1. Filtration The renal artery carries blood into the kidney (approximately 600 mis of blood enters a kidney each minute). The renal artery then branches into arterioles which then branch intoaspecialized capillaries called the glomerulus. Because of the great difference in diameter between the renal artery and the glomerul us, blood entering the glomerulus is under very high pressure. This pressure forces about 20% of the blood plasma (about 120m1 of the 600 ml) out of the glomerulus and across the membrane of Bowman's

capsule. Bowman's capsule acts to "filter" or separate some of the substances that are located in blood plasma from others. This is because some substances are small enough to fit through the pores of the membrane of Bowman's capsule and some are too large and thus do not enter Bowman's capsule with