Final answer:
The depressor anguli oris is a facial muscle that lowers the corners of the mouth, producing a frowning or sad expression.
Step-by-step explanation:
The depressor anguli oris is a facial muscle that is responsible for lowering the corner of the mouth. It is located underneath the skin at the corners of the mouth and works in opposition to the muscles that raise the corners of the mouth. When the depressor anguli oris contracts, it pulls the corners of the mouth downward, producing a frowning or sad expression.
For example, when someone is feeling down or unhappy, the depressor anguli oris may be more active, causing the corners of their mouth to turn downward.
The depressor anguli oris is just one of the many muscles of facial expression that allow us to convey emotions and perform various movements of the face.