For the vast majority of us, a hiccup is no more than a slight nuisance that goes away quite quickly on its own, or with a little coaxing from one of the huge number of folk remedies available. Hiccups, however, can be a serious affliction - they have even killed some long-term sufferers.
But what exactly is a hiccup? Is your breath going out or in? If you think about it, you realise that there is a feeling of inhaling. This is, in fact, exactly what is going on: your diaphragm pulls down as if you were taking a big breath, and your so-called 'inspiratory' muscles hastily work to make room for the incoming air in your chest. Next, however, instead of air rushing in to fill the space being created in your chest, something else happens. Within thirty-five milliseconds, a signal reaches your glottis - the little flap that covers your airway (or 'trachea') when you swallow so that food doesn't go down it - telling the glottis to slam shut. This keeps any air from actually getting into your lungs - and causes the "hic" associated with a hiccup.
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