A kidney consists of several excretory units, called nephrons, that work together to produce urine. They are called the filtering (functional) units of the urinary system. The main parts of the nephrons are: the glomerulus or the Malpighian body, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tube and collecting tube, which work together to filter the plasma that enters the nephrons through the blood vessels. The chemical processes through which filtration takes place are: osmosis, passive diffusion and active transport of molecules.