diaphragm

Hiccups come from a three-part nerve reflex arc that fires the diaphragm early and snaps the vocal cords shut. Here is the mechanism, in detail.

Your lungs perform roughly 20,000 breath cycles per day, quietly swapping carbon dioxide for oxygen across a surface the size of a tennis court — all folded into a chest cavity the size of a shoebox. Here is the full mechanism, from the diaphragm's first pull to the moment oxygen binds hemoglobin.

Hiccups are involuntary diaphragm spasms. Learn the neuroscience, evolutionary origins, common triggers, and when hiccups become a medical concern.