The right part of the heart is concerned with venous blood and left part with the oxygenated blood. In one complete circuit in the body the blood passes twice through the heart, once through its right side and then through its left side.
The different sizes and types of blood vessels are involved in blood circulation. They range from thick-walled, wide vessels of 1 cm in diameter to fine capillaries with a diameter of a few microns.
The left auricle receives oxygen-rich blood from the lungs. The oxygenated blood is carried from the lungs to the left auricle by four pulmonary veins. The left ventricle receives blood from the left auricle. The left ventricle pumps the blood into the biggest blood vessel of the body- aorta which distributes oxygen-rich blood to different parts of the body.