Across all species, the cardiovascular system performs in almost the same way. It transfers blood that has no oxygen in it to, and through, the heart and lungs to combine fresh oxygen with blood. However, the small details in specific animals and organisms are what separate them from others. For example, due to the massive size of the African Bull Elephant, its heart can way up to 28kg; an enormous number compared to most hearts, and even some animals. The elephant even has arteries that are so massive, and so long, that they are supported by their very own "elastic fibers and muscles", and have much thicker walls than the veins of most other animals. The veins and blood vessels are so big, exceeding 35 centimeters, that an elephant's high blood pressure is imperative to ensure that each blood vessels are sturdy and don't collapse. One unusual, and quite unique aspect of the elephants heart is that it is separated at the top of the ventricles. Also, the ventricles are paired with venae cavae rather than a single vein, which is the usual pairing.