Zygomaticus Major

The zygomaticus major is yet another muscle that inserts into the corner of the mouth. It originates, as its name implies, from the zygomatic bone. As it runs diagonally it pulls the corner of the mouth superiorly in addition to laterally. This muscle is important in that a smile that just involves the risorius looks unnatural while genuine smiles involve the zygomaticus muscles.

Figure 11.

Figure 11.

Diagram Reference Guide