A medical pump (1), comprising a reservoir (3) having a part that encloses fluid； a tubular element (7), the interior of which can be arranged in deflected communication with the part that encloses fluid to allow the fluid (5) to pass to the tubular element (7)； an inner seal (15) that can be moved inside the tubular element (º) between an advanced position and a removed position, where the inner seal 15 can be removed from the advanced position to allow the fluid (5) to be transfer from the part that encloses fluid to the internal space 21 defined by the tubular element (7) and the inner seal closed (15), and in which the inner seal 15 can be advanced from the withdrawn position to discharge out of the pump the fluid (5) present in said internal space 21 ；. characterized in that said part that encloses fluid contains a volume of fluid (5) tightly closed to the communication with air and the part that encloses fluid is adapted to reduce in volume essentially to the same extent as any volume of fluid transferred to said internal space 21 of the tubular element (7) and said part that encloses fluid comprises an external seal (9) that can be moved inside the reservoir (3) and that defines a delimitation of the fluid (5) contained in the part that encloses fluid, being arranged the outer seal (9) to move relative to the tubular element (7) when the inner seal 15 is removed from said advanced position.Una bomba medica (1), que comprende un depósito (3) que tiene una parte que encierra fluido； un elemento tubular (7), cuyo interior se puede disponer en comunicación para paso defluidos con la parte que encierra fluido para permitir que el fluido (5) pase al elemento tubular (7)；. un cierre hermetico interior (15) que se puede mover dentro del elemento tubular (º) entre una posición avanzada y una posición retirada, en donde el cierre hermetico interior 15 se puede retirar desde la posición avanzada para permitir que el fluido (5) se transfiera desde la parte que encierra f
