An artificial sphincter containing, in use, a pressurizing fluid, said artificial sphincter comprising: an inflatable occlusion means for occluding a body passage, a stretchable fluid reservoir, a pump means having a first port in fluid communication with said occlusion means via a first tube and a second port in fluid communication with said fluid reservoir via a second tube for selectively transferring the pressurizing fluid from said occlusion means to said reservoir to deflate said occlusion means so that a blocked body passage may be opened; a compressible bulb which is attached to the pump means and which, in use, contains part of the pressurizing fluid, a balloon holder having a lumen which establishes fluid communication in between said fluid reservoir and said second tube, a pressure compensation balloon which is in fluid communication with the lumen of said balloon holder and which, in use, is to be implanted in the abdomen of a patient, wherein said pump means comprises; a lumen, whose first end has a ball seating and a ball accommodated on said seating and whose second end is open to the bulb, a blockage seat which is located in the entry of first port and which is sized and shaped to block fluid flow towards the first port when, the ball is forced to lean on the blockage seat by the pressurized fluid coming from the bulb, a chamber in which the ball is movable, said chamber being located in between blockage seat and the ball seating, wherein, when the bulb is squeezed, the pressurizing fluid contained in the bulb passes around the ball and enters the chamber and then flows through the second port towards the stretchable fluid reservoir, characterized by one or more resilient lips located circumferentially above (+y) the ball in the chamber, wherein the annular cavity formed by the distal ends of the resilient lips has a diameter which is less than the diameter of the ball so that the ball can be guided towards the blockage seat by the resilient lips when the bulb is squeezed. an inflatable occlusion means for occluding a body passage, a stretchable fluid reservoir, a pump means having a first port in fluid communication with said occlusion means via a first tube and a second port in fluid communication with said fluid reservoir via a second tube for selectively transferring the pressurizing fluid from said occlusion means to said reservoir to deflate said occlusion means so that a blocked body passage may be opened; a compressible bulb which is attached to the pump means and which, in use, contains part of the pressurizing fluid, a balloon holder having a lumen which establishes fluid communication in between said fluid reservoir and said second tube, a pressure compensation balloon which is in fluid communication with the lumen of said balloon holder and which, in use, is to be implanted in the abdomen of a patient, wherein said pump means comprises; a pressure compensation balloon which is in fluid communication with the lumen of said balloon holder and which, in use, is to be implanted in the abdomen of a patient, wherein said pump means comprises; a lumen, whose first end has a ball seating and a ball accommodated on said seating and whose second end is open to the bulb, a blockage seat which is located in the entry of first port and which is sized and shaped to block fluid flow towards the first port when, the ball is forced to lean on the blockage seat by the pressurized fluid coming from the bulb, a chamber in which the ball is movable, said chamber being located in between blockage seat and the ball seating, wherein, when the bulb is squeezed, the pressurizing fluid contained in the bulb passes around the ball and enters the chamber and then flows through the second port towards the stretchable fluid reservoir, characterized by one or more resilient lips located circumferentially above (+y) the ball in the chamber, wherein the annular cavity formed by the distal ends of the resilient lips has a diameter which is less than the diameter of the ball so that the ball can be guided towards the blockage seat by the resilient lips when the bulb is squeezed.