The orbicularis oris muscle is also responsible for closing the mouth. In the past, the muscle was thought to be a sphincter, which is a ring-like muscle used to open or close an area of the body.

The depressor anguli oris muscle is attached to the lower jaw (mandible). It ends at the orbicularis oris, which is the ring-like muscle that encompasses the lips. It is attached at the edge of the ...

Faces of a wild gray wolf, a Golden Retriever domesticated dog, and a human, along with tissue samples from the orbicularis oris muscle for each species. In the photos the dog and human are actively ...