Arterial blood flows from the pulmonary veins into the left atrium and left ventricle, is pumped into the aorta, and travels through the body’s circulation to reach the major, medium, and small arteries and capillaries throughout the body.
Arterial blood is blood with a high oxygen and low carbon dioxide content after alveolar gas exchange, not blood flowing in the arteries. The blood in the pulmonary capillaries after gas exchange is arterial blood, which sinks into the pulmonary veins, enters the left atrium via the pulmonary vein valve, and enters the left ventricle via the mitral valve.
The arterial blood in the left ventricle is pumped into the aorta via the aortic valve with the contraction of the heart, and transported to the major, medium, and small arteries throughout the body, and completes the gas exchange in the capillary network throughout the body, delivering oxygen and recycling carbon dioxide for the tissues, and turning into the venous blood with a low blood oxygen content and a high carbon dioxide content.
Venous blood flows back into the superior and inferior vena cava through the veins, and is ejected into the pulmonary artery through the right atrium and right ventricle to reach the pulmonary capillary network, and then becomes arterial blood after gas exchange. The cycle begins again and again.