What muscle extends from the cheekbones to the angles of the mouth and elevates the lip when laughing?

The muscle that extends from the cheekbones to the angles of the mouth and elevates the lip when laughing is the zygomaticus. This muscle plays a key role in facial expressions, particularly those associated with smiling. The zygomaticus muscle consists of two parts: the zygomaticus major and zygomaticus minor. When it contracts, it pulls the corners of the mouth upward, creating the smile that is typically associated with happiness and laughter.

The anatomy of the zygomaticus is such that it originates from the zygomatic bone (cheekbone) and inserts into the skin at the corners of the mouth. This positioning allows it to effectively elevate the lip and contribute to the expression of joy.

In contrast, the orbicularis oris is a circular muscle around the mouth responsible for closing and puckering the lips, while the risorius contributes to pulling the mouth sideways, and the buccinator is more involved in helping to hold food in place while chewing rather than elevating the lip. Thus, the unique role of the zygomaticus in lifting the lip during laughter clearly identifies it as the correct answer.