Blood circulation and continuity of trade.The blood circulation ensures the supply of nutrients and oxygen to the organs, it also transports waste to the kidneys and carbon dioxide to the lungs. I) Blood circulates one way in a closed circulatory system.Blood circulates in one closed circulatory system: Arteries, large blood vessels rich in muscle fibers,
bring blood to organs from the heart, pulmonary artery and artery Aorte; In contact with the organs the blood circulates in very branched networks of very fine blood vessels: the capillaries; The pulmonary veins and the Cave vein, elastic vessels, bring blood back to the heart. II) The movement of the blood through the heart. The heart is a hollow muscle, which unites two independent parts: the right heart and the left heart. Each right and left part is formed of an auricle which receives the blood from the veins, and then from a ventricle which, in contracting, expels the blood into the artery. The rhythmic contractions of the right ventricle and the left ventricle place the blood in motion. III) The double circulation of blood. The blood follows a double path in the body: The pulmonary circulation, coming from the right heart, allows the respiratory exchanges with the lungs. The blood leaves the heart through the pulmonary artery, passes through the networks of the pulmonary capillaries, where there is gas exchange with the air contained in the pulmonary alveoli and then returns to the left heart by four pulmonary veins. The general circulation, coming from the left heart, allows the exchanges with all the other organs. The blood leaves the heart through the aorta artery, it is led into the capillaries of all the organs of the body, and then returns to the right heart through the vena cava. Good diet, exercise and a healthy lifestyle are important to maintain a functioning circular system and to reduce the risk of cardiovascular disease, atherosclerosis and heart attacks.