Centrifugation systems and methods are provided for separating blood into its constituent parts. Inner and outer walls of a centrifuge each include a projection which extends toward the other wall. A separation chamber is received in the centrifuge between the walls, with the chamber including an inlet port for flowing blood into the chamber, a plasma outlet port for flowing plasma out of the chamber, and a red cell outlet port for flowing red blood cells out of the chamber. With the chamber received in the centrifuge between the walls, the first projection extends into the path of separated blood components flowing toward the plasma outlet port and prevents cellular blood components from flowing into the plasma outlet port. The second projection extends into the path of separated blood components flowing toward the red cell outlet port and prevents plasma from flowing into the red cell outlet port.