Plural of emissarium; channels or openings, especially in anatomy or engineering, through which something is sent out or discharged.
From Latin emissarium (an outlet or drain), derived from emittere (to send out), combining e- (out) + mittere (to send).
Medical students learn about the 'emissaria' in the skull—tiny channels that allow blood vessels to pass through, and their name literally describes their function: they're the 'outlets' for those vessels.
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