Pressure Gradients: No Sucking Involved

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  1. In the article about “sucking” through a straw, you state that you are actually inhaling. But I don’t believe your lungs are involved at all. We somehow create a partial vacuum in our mouth. You can create and maintain this partial vacuum while inhaling and exhaling through through your nose. Try it. You can create this partial vacuum by enlarging the oral cavity. Thus, if you seal your lips and open your jaw, you enlarge the oral cavity, creating the partial vacuum. This is how infants drink through the nipple on the bottle. This is easily observable. An infavt drinking through a nipple appears to be chewing, as it constantly enlarges and reduces its oral cavity. Older children and adults don’t do this. I still haven’t figure out exactly how we create and maintain the partial vacuum without using our lungs. Joe Schaum.


    1. Britannica describes suckling in infants: ” A partial vacuum is created in the oral cavity by retracting the tongue to the back of the mouth. The rear portion of the tongue seals against the roof of the mouth, allowing liquids to be drawn into the front region. When the oral cavity is full, the tongue relaxes, and fluids flow back to the throat to be swallowed.” But when older children or adults use a straw, the lungs are involved because the chest moves during the sucking action.


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