The blood circulation is the physiological process of the transport of arterial and venous blood by the cardiovascular system, which consists of heart and vessels. The circulation is powered by the pumping funtion of the heart. The circulatory system is devided into systemic circulation and pulmonary circulation, which are arranged behind one another, so that the blood has to pass through both. The systemic circulation starts in the left ventricle of the heart. It contracts and pumps oxygenated blood into the aorta, then into the downstream arteries then arterioles and finally capillaries of the body. From the capillaries the blood flows back towards the heart and arrives at the right atrium. The pulmonary cicrulation starts at the right ventricle of the heart. It contracts and pumps de-oxygenated bloof into the pulmonary arteries and the connected lung capillaries. From the capillaries the blood returns to the heart via the pulmonary veins and arrives at the left atrium, where it starts the cycle again.
