The NephronThe nephrons are the functional units of the kidneys. There are three main functions of the nephrons: (1) control blood concentration and volume by removing selected amounts of water and solutes, (2) regulate blood pH, and (3) remove toxic wastes from the blood. The physiology of the nephron consists of three main processes: (1) filtration, (2) reabsorption, and (3) secretion. Filtration• Occurs in the glomerulus• Water and small molecules dissolved in the blood are forced out of the glomerulus and into Bowman’s capsule. This fluid that is generated is called the filtrate. Large substances such as blood cells and large proteins remain in the bloodstream; they are too large to exit through the pores of the capillaries of the glomerulus. Reabsorption• Occurs along the length of the tubule.• Involves the movement of substances that are needed by the blood from the filtrate and back into the peritubular capillaries that surround the renal tubule.Secretion• Occurs along the length of the tubule.• Involves movement of substances in the opposite direction as reabsorption. The substances that move from the peritubular capillaries into the renal tubule are substances that the blood doesn’t need such as excess hydrogen ions (H+), which would make the blood less acidic, and potassium ions.

glomerulus

entering arteriole

exiting venule

proximal convoluted tubule

peritubular capillaries

collecting duct

ascending loop of Henle

des cending loop of Henle

glomerular capsule(Bowman’s capsule)

distal convoluted tubule