The urinary and circulatory systems work together mainly in the unit of the kidneys. The kidneys are a part of the urinary system, but they are also able to help regulate the circulatory system by filtering the blood and allowing it to become more regulated.
The blood enters the urinary system after traveling through the body. This is one of the last stops that it makes before it is circulated back to the heart where it will begin its journey again. It enters into a special part of the kidneys that allows the pH levels to become balanced; blood pressure is lowered with the addition of renin in the kidney area.
The kidneys must be able to function properly in order for the circulatory system to function properly. Likewise, the circulatory system must be functioning properly in order deliver the blood to the kidneys where filtering occurs. Kidneys may have decreased function due to infections or diseases, but when kidneys stop working completely the circulatory system will also stop working. There are special procedures, such as dialysis, that allow the blood to continue to be filtered outside of the body without the need for the kidneys to be functioning completely.