After blood is centrifuged, the top layer, which constitutes 55 percent of the total blood volume, is known as the ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ .