Head for dispensing a product, particularly a pasty product, and dispenser equipped with this head

Head for dispensing a product, comprising a nozzle piece adapted to be placed on a container (5, 105, 205) containing the product to be dispensed, this nozzle piece including a base (4, 104, 204) equipped with a sleeve (6, 106, 206) in which is fastened a component to which a pump (14, 114, 214) is linked, sealing means between the nozzle piece (2, 102, 202) and the component (11, 111, 211) in order to interact when this component has been fully seated on the sleeve of the nozzle piece, the nozzle piece (2, 102, 202) having retention means (R) capable of holding the component (11, 111, 211) in an only partially seated position in which the sealing means (8, 108, 208) between the component and nozzle piece do not yet interact, and passage means (16, 116, 216) between an outer surface of the component (11, 111, 211) and an inner surface of the sleeve (6, 106, 206) in which the component is engaged in the partially seated position in order to maintain a communication between the inside of the container (5, 105, 205) and the outside in only the partially seated position.