The deoxygenated blood is collected from the body tissues through the veins which further combine to form vena cava. This vena cava pours deoxygenated blood collected from the body tissues into the right auricle of heart. From right auricle it goes to right ventricle and from here the blood is pumped into the pulmonary artery which takes the deoxygenated blood from heart to the lungs. In the alveoli of lungs the blood is oxygenated. This oxygenated blood is pumped into the pulmonary veins which pours the blood into the left auricle. From here the oxygenated blood is poured into the left ventricle. The left ventricle pushes the blood into the aorta which pumps the oxygenated blood into the body tissues and supply oxygen through the tissues for various body functions.
