Not only does it act as a waterproof barrier allowing cells to live in a fluid environment even in relatively dry air, as does human skin, it also allows available environmental moisture to be extracted for use by the body. The average Vulcan heart rate is 242 beats per minute. This is explained in part by the extremely dilated blood vessels of Vulcans. Larger diameter blood vessels are an additional aid in cooling the body, allowing for greater cooling surface. The Vulcan heart is located where one would expect to find the Terran liver, leaving room for the somewhat larger Vulcan lung assembly.
Vulcan blood is a copper-based compound and is green in clolour.
Copper-based life aids in the utilization of oxygen under the low atmospheric pressure, low oxygen conditions on Vulcan. Blood cells are biconvex in contrast to the concave cells of Terrans. This convex shape also aids in cooling individual blood cells, the entire blood stream, and finally the entire Vulcan body. The Vulcan lung is somewhat larger in size than Terran lungs. The Vulcan heart is also somewhat larger by Terran standards, but well within the normal range for humans.