Kidneys and urinary system
The kidneys filter out the waste products from the blood that the body does not need. Every kidney has a million small filters, that constantly separate out part of the blood and fluids flowing through the body's circulation. Essentials like salt and nutrients then flow back into the body. Wastes are sent through the bladder and urinary system until they are released from the body as urine. At the same time kidneys also help regulate blood pressure.