The buccinator muscle is the major facial muscle underlying the cheek. It holds the cheek to the teeth and assists with chewing.
The buccinator muscle is served by the buccal branch of cranial nerve VII, also known as the facial nerve.
The buccinator is one of the first muscles that a human can control; the sucking reflex of a baby depends on it. Smiling, chewing, and whistling are all dependent upon it, and speech would be difficult and slurred without its proper function.
If the facial nerve is impaired, as in Bells Palsy or by a stroke, the buccinator is often paralyzed, thus making all functions dependent upon it difficult or impossible.
The buccinator muscle and its proper function are of special interest to speech therapists. Because it is the muscle that spreads the mouth wide, bilabial fricative sounds — not used in English but used for Spanish [b] and [v] sounds — and certain sounds that require the mouth to be wider — like the [i] and [e] sounds — are impaired when the buccinator does not work properly. The buccinator muscle also controls the amount of open space in the mouth, affecting many other vocal factors like tone and echo.