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。
，
;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。
明：以
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