In the open circulatory system, blood is pumped into open cavities by the heart. Blood vessels transport blood at low pressure from the open cavities through the whole body. In the open circulatory system, there are no major veins or arteries that direct blood distribution or increase blood pressure. In the open circulatory system, all tissues and organs are bathed by the blood throughout the body.
In the closed circulatory system, blood is always transported to the arteries and then to the veins for circulation. The veins then distribute the blood all over the body. In addition, blood does not bathe all organs and tissues in a closed circulatory system. Instead, blood is retained in the vessels and taken to all body extremities at high pressure.