The zygomaticus muscle inserts on which part of the body?

The zygomaticus muscle is involved in facial expression and specifically aids in smiling. It originates from the zygomatic bone and inserts at the skin of the corner of the mouth. This insertion allows the zygomaticus muscle to elevate the corners of the mouth, which plays a critical role in creating the expression of happiness or joy.

The other options do not correctly represent the anatomical relationship of the zygomaticus muscle. The skin of the forehead is influenced by other muscles such as the frontalis, while the sclera of the eye relates to the muscles controlling eye movement. The neck muscles, such as those involved in neck movement or those associated with facial expressions, do not interact with the zygomaticus muscle, which is strictly a facial muscle. Therefore, the correct insertion of the zygomaticus muscle is indeed at the skin of the corner of the mouth, as it is vital for facial expressions.