An injection port assembly (10, 110), comprising: a body (12, 112) having a first mating structure (14, 114) and a second mating structure (16, 116) configured to be coupled to the first mating structure (14, 114); a resilient barrier (20, 120) configured to be received within the body (12, 112) and compressible from a less compressed first position in which fluid flow through the injection port assembly (10, 110) is blocked to a more compressed second position in which fluid flow through the injection port assembly (10, 110) is permitted, the resilient barrier (20, 120) including an internal cavity (22, 122); and a hollow cannula (24, 124) coupled to the first mating structure (14, 114) and configured to be received within internal cavity (22, 122) of the resilient barrier (20, 120), the hollow cannula (24, 124) having a longitudinal central axis (11, 111), the hollow cannula (24, 124) including: a cannula distal end portion (44, 144) configured to extend through the resilient barrier (20, 120) when the resilient barrier (20, 120) is in the more compressed second position; at least one lateral outlet window (46, 48, 146, 147, 148) formed in the cannula distal end portion (44, 144) the at least one lateral outlet window (46, 48, 146, 147, 148) having a window width (50, 150) perpendicular to the longitudinal central axis (11, 111); and characterized in that, an internal fluid passageway (62, 162) defined in the hollow cannula (24, 124) and configured to communicate the at least one lateral outlet window (46, 48, 146, 147, 148) with a fluid conduit connected to the first mating structure (14, 114), the internal fluid passageway (62, 162) having a non-circular cross section taken in a plane perpendicular to the longitudinal axis, the non-circular cross section extending axially proximal from the window (46, 48, 146, 147, 148), the non-circular cross section having a cross section area greater than a cross section area of a circle of diameter equal to the window width (51, 151). a body (12, 112) having a first mating structure (14, 114) and a second mating structure (16, 116) configured to be coupled to the first mating structure (14, 114); a resilient barrier (20, 120) configured to be received within the body (12, 112) and compressible from a less compressed first position in which fluid flow through the injection port assembly (10, 110) is blocked to a more compressed second position in which fluid flow through the injection port assembly (10, 110) is permitted, the resilient barrier (20, 120) including an internal cavity (22, 122); and a hollow cannula (24, 124) coupled to the first mating structure (14, 114) and configured to be received within internal cavity (22, 122) of the resilient barrier (20, 120), the hollow cannula (24, 124) having a longitudinal central axis (11, 111), the hollow cannula (24, 124) including: a cannula distal end portion (44, 144) configured to extend through the resilient barrier (20, 120) when the resilient barrier (20, 120) is in the more compressed second position; at least one lateral outlet window (46, 48, 146, 147, 148) formed in the cannula distal end portion (44, 144) the at least one lateral outlet window (46, 48, 146, 147, 148) having a window width (50, 150) perpendicular to the longitudinal central axis (11, 111); and a cannula distal end portion (44, 144) configured to extend through the resilient barrier (20, 120) when the resilient barrier (20, 120) is in the more compressed second position; at least one lateral outlet window (46, 48, 146, 147, 148) formed in the cannula distal end portion (44, 144) the at least one lateral outlet window (46, 48, 146, 147, 148) having a window width (50, 150) perpendicular to the longitudinal central axis (11, 111); and characterized in that, an internal fluid passageway (62, 162) defined in the hollow cannula (24, 124) and configured to communicate the at least one lateral outlet window (46, 48, 146, 147, 148) with a fluid conduit connected to the first mating structure (14, 114), the internal fluid passageway (62, 162) having a non-circular cross section taken in a plane perpendicular to the longitudinal axis, the non-circular cross section extending axially proximal from the window (46, 48, 146, 147, 148), the non-circular cross section having a cross section area greater than a cross section area of a circle of diameter equal to the window width (51, 151).