A breast pump for extracting milk from a human breast includes an extracting cup and has an engagement portion for engaging the breast. A container has a mouth portion connected to the extracting cup. A milk receiving bag is mounted to the mouth portion and suspended in the container. An air suction source is connected to the container in order to produce air suction inside the container. An air path connects the interior of the extracting cup and the inside of the container, wherein the air suction creates a negative air pressure condition to assist in the suction of milk. The milk flows by gravity through the extracting cup and into the milk receiving bag without contact with the air suction source or the inside of the container.