Which muscle is responsible for pulling up the corner of the mouth?

The muscle responsible for pulling up the corner of the mouth is the zygomaticus. This muscle is located in the cheek area and plays a crucial role in facial expressions, particularly in smiling. When the zygomaticus contracts, it elevates the corners of the mouth, creating a smile or a grin. This muscle has two components: the zygomaticus major and the zygomaticus minor, both of which assist in raising the mouth's corners.

In contrast, the orbicularis oris surrounds the mouth and is primarily involved in movements like closing and puckering the lips. The masseter is a powerful muscle involved in chewing, facilitating the movement of the jaw rather than influencing the corners of the mouth. Finally, the buccinator helps keep food between the teeth while chewing and assists in blowing air, but it does not pull up the mouth's corners. Understanding the unique functions of these muscles clarifies why the zygomaticus is specifically the muscle that elevates the corners of the mouth.