Buccinator

The buccinator is a thin, quadrilateral-shaped paired muscle that forms the muscular portion of the cheek, providing its main structural and functional component. It occupies the space between the maxilla and mandible and is covered by the buccopharyngeal fascia. Although it lies in the facial region, the buccinator is not typically considered a muscle of facial expression but rather a muscle of mastication. Because many other muscles overlay and intermingle with it, the buccinator is also involved in certain facial expressions.