An airfoil for a turbine blade, the airfoil comprising: a first pressure side cavity positioned adjacent a pressure side, the first pressure side cavity configured to receive a coolant; at least one distinct pressure side cavity positioned adjacent to and fluidly coupled to the first pressure side cavity; a trailing edge positioned between the pressure side and a suction side; at least one suction side cavity positioned adjacent the suction side; and a trailing edge cooling system positioned adjacent the trailing edge and in direct fluid communication with the first pressure side cavity, the trailing edge cooling system comprising a plurality of cooling circuits each including: an outward leg extending axially between the trailing edge and the first pressure side cavity, the outward leg in direct fluid communication with the first pressure side cavity via an opening formed through a side wall; characterized in having: a return leg extending axially between the trailing edge and the at least one suction side cavity, the return leg in direct fluid communication with the at least one suction side cavity; and a turn positioned adjacent the trailing edge, the turn fluidly coupling the outward leg and the return leg, the cooling system configured to receive a portion of the coolant from the first pressure side cavity. a first pressure side cavity positioned adjacent a pressure side, the first pressure side cavity configured to receive a coolant; at least one distinct pressure side cavity positioned adjacent to and fluidly coupled to the first pressure side cavity; a trailing edge positioned between the pressure side and a suction side; at least one suction side cavity positioned adjacent the suction side; and a trailing edge cooling system positioned adjacent the trailing edge and in direct fluid communication with the first pressure side cavity, the trailing edge cooling system comprising a plurality of cooling circuits each including: an outward leg extending axially between the trailing edge and the first pressure side cavity, the outward leg in direct fluid communication with the first pressure side cavity via an opening formed through a side wall; characterized in having: a return leg extending axially between the trailing edge and the at least one suction side cavity, the return leg in direct fluid communication with the at least one suction side cavity; and a turn positioned adjacent the trailing edge, the turn fluidly coupling the outward leg and the return leg, the cooling system configured to receive a portion of the coolant from the first pressure side cavity. an outward leg extending axially between the trailing edge and the first pressure side cavity, the outward leg in direct fluid communication with the first pressure side cavity via an opening formed through a side wall; characterized in having: a return leg extending axially between the trailing edge and the at least one suction side cavity, the return leg in direct fluid communication with the at least one suction side cavity; and a turn positioned adjacent the trailing edge, the turn fluidly coupling the outward leg and the return leg, the cooling system configured to receive a portion of the coolant from the first pressure side cavity.