The risorius and the buccinator muscles assist in the retraction of the lips, as well as support entrapment of air within the oral cavity.
笑肌和颊肌帮助唇的收缩,也支撑了整个口腔的气体流通。
英语百科
Buccinator muscle
The buccinator (/ˈbʌksɪneɪtər/
) is a thin quadrilateral muscle, occupying the interval between the maxilla and the mandible at the side of the face. It forms the anterior part of the cheek or the lateral wall of the oral cavity.