Risorius

The risorius (Latin: musculus risorius) is a muscle of facial expression located laterally to the opening of the oral cavity. It is classified as the buccolabial facial muscle. The risorius pulls the angle of the mouth laterally.

Origin

The risorius originates from the masseteric fascia.

Insertion

The risorius inserts into the skin at the angle of the mouth.

Action

Upon activation, the risorius pulls the angle of the mouth laterally. Contractions of the risorius muscle produce facial expressions of pleasure and laughter.

Innervation

The risorius is innervated by the buccal branch of the facial nerve (CN VII).

Blood supply

The risorius muscle is mainly supplied by the superior labial branch of the facial artery.