A turbine blade including an airfoil defining an airfoil cavity forming a cooling system in the blade. First, second and third ribs are positioned in the airfoil cavity to form first, second and third generally elongated cooling cavities along at least a portion of the span-wise direction of the airfoil in an area adjacent the trailing edge of the airfoil. Each of the ribs includes a plurality of orifices for conveying a cooling fluid into each of the cavities. Each of the cavities includes a pair of converging walls, angling inwardly relative to an outer surface of the airfoil, to increase the impingement of cooling fluid from the orifices onto the cavity walls, and increase the cooling effectiveness within the trailing edge of the airfoil.