Parts of the kidney and how it filters waste from the blood

The kidneys remove waste and extra fluid from the blood through filtering units called nephrons. Each nephron contains a filter, called a glomerulus. Each filter has tiny blood vessels called capillaries. When blood flows into a glomerulus, tiny bits of water, minerals and nutrients, and waste pass through the walls of a capillary. These bits are called molecules. Larger molecules, such as proteins and red blood cells, do not move through the walls of a capillary. The molecules that are filtered out pass into another part of the nephron called the tubule. The water, nutrients and minerals the body needs are sent back to the bloodstream. The extra water and waste become urine that flows to the bladder.