The risorius muscle is a large facial muscle. This muscle is located on the sides of the mouth and is primarily responsible for creating facial expressions.
The risorius begins around the parotid gland, a salivary gland in the back of the jaw, and wraps around the platysma muscle, a muscle located in the chest and neck. The risorius continues to the skin of the corner of the mouth, where it ends. The facial nerve is directly connected to the risorius muscle.
The risorius works by expanding and contracting in an upward and outward motion. It works with other facial muscles to create a whole facial motion that pulls the lips and face back. Smiling and frowning are two of the facial expressions that are created by all of the facial muscles working together.