Lips are the external part of the mouth. They include an upper and a lower lip, and are responsible for enabling articulation and moving food around the oral cavity. This opening is made up of a versatile sphincter muscle, meaning the lips can adopt a multitude of different forms. Furthermore, the term "lip" can also be used to refer to the edges of a wound and the cutaneous folds of the vulva. In this last case, the lips are categorized as small and large, or more often referred to as the labia.