A hollow muscular organ that pumps the blood through the circulatory system by rhythmic contraction and dilation. In vertebrates there may be up to four chambers (as in humans), with two atria and two ventricles.
The heart
They carry blood from the right side of the heart to the lungs.
The pulmonary arteries
The main artery of the body, supplying oxygenated blood to the circulatory system. In humans it passes over the heart from the left ventricle and runs down in front of the backbone.
The aorta
Unlock this slideshow and over 2 million more with Baamboozle+