The flow of blood in the kidneys begins with the renal artery. Eventually the blood is filtered through the glomerulus, where specific substances flow into the capsule. The afferent (approaching) arteriole is larger than the efferent (exiting) arteriole which helps maintain a high pressure in the glomerulus to increase GFR. Blood flows from efferent arterioles into either vasa recta (juxtamedullary nephron) or peritubular capillaries (cortical nephron). Blood leaves via the renal vein.