A turbine blade or vane comprising: an aft cooling circuit that extends between a midsection and a trailing end of the turbine blade or vane, the aft cooling circuit including a trailing end section proximate the trailing end, a first interior section proximate the midsection and functioning as an inlet for receiving a first bleed flow, and a first intermediate section fluidly connected between the trailing end section and the first interior section; and a forward cooling circuit that extends between the midsection and a leading end of the turbine blade or vane, the forward cooling circuit including a leading end section proximate the leading end, a second interior section proximate the midsection and functioning as an inlet for receiving a second bleed flow, and a plurality of second intermediate sections fluidly connected between the leading end section and the second interior section, wherein: the leading end section includes a plurality of first coolant discharge openings (96a,96b,96c,96d); the first intermediate section includes a plurality of third coolant discharge openings; and the trailing end section includes a plurality of fourth coolant discharge openings characterised in that the plurality of second intermediate sections includes a pair of second intermediate sections, one of the pair being adjacent the leading end section and the other of the pair being adjacent the second interior section and the one of the pair that is adjacent the leading end section includes a plurality of second coolant discharge openings, the plurality of second coolant discharge openings each including a constant cross-section portion and a tapered portion that opens to the surface of the turbine blade or vane. an aft cooling circuit that extends between a midsection and a trailing end of the turbine blade or vane, the aft cooling circuit including a trailing end section proximate the trailing end, a first interior section proximate the midsection and functioning as an inlet for receiving a first bleed flow, and a first intermediate section fluidly connected between the trailing end section and the first interior section; and a forward cooling circuit that extends between the midsection and a leading end of the turbine blade or vane, the forward cooling circuit including a leading end section proximate the leading end, a second interior section proximate the midsection and functioning as an inlet for receiving a second bleed flow, and a plurality of second intermediate sections fluidly connected between the leading end section and the second interior section, wherein: the leading end section includes a plurality of first coolant discharge openings (96a,96b,96c,96d); the first intermediate section includes a plurality of third coolant discharge openings; and the trailing end section includes a plurality of fourth coolant discharge openings characterised in that the plurality of second intermediate sections includes a pair of second intermediate sections, one of the pair being adjacent the leading end section and the other of the pair being adjacent the second interior section and the one of the pair that is adjacent the leading end section includes a plurality of second coolant discharge openings, the plurality of second coolant discharge openings each including a constant cross-section portion and a tapered portion that opens to the surface of the turbine blade or vane. the leading end section includes a plurality of first coolant discharge openings (96a,96b,96c,96d); the first intermediate section includes a plurality of third coolant discharge openings; and the trailing end section includes a plurality of fourth coolant discharge openings characterised in that the plurality of second intermediate sections includes a pair of second intermediate sections, one of the pair being adjacent the leading end section and the other of the pair being adjacent the second interior section and the one of the pair that is adjacent the leading end section includes a plurality of second coolant discharge openings, the plurality of second coolant discharge openings each including a constant cross-section portion and a tapered portion that opens to the surface of the turbine blade or vane.