Air-filled spaces within the bones of the skull and face, connected to the nasal cavity.
From Latin 'sinus' meaning 'curve' or 'bay,' referring to the curved, hollow spaces. The anatomical term was adopted because these cavities resemble curved bays or inlets in the skull.
Your sinuses are basically caves in your head - evolutionary air pockets that make your skull lighter while keeping it strong. When they're blocked, you're experiencing your own personal underground flood in these cranial caverns!
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