What is the principle of hand pump sprayers

Hand pump sprayers is to work according to the relationship between flow rate and pressure of gas. When the hand sprayer piston, the velocity of air flow into the upper Straw liquid in hand pump sprayers  up, reduce the pressure, and the liquid medicine bottle is equal to the air pressure above the outside atmospheric pressure, thus makes the air pressure is greater than the pressure above the liquid backpack pressure sprayers  Straw mouth, hand pump sprayers at atmospheric pressure under, put the medicine on the hydraulic Straw, then from the front end of the ejection of pelvic.