Incisivi labii, the incisive muscles of the lips (upper and lower), originate in the medial parts of the upper and lower jaw, respectively, run through the upper and lower lips, and insert near the corners of the lips. Their action pulls the corners of the lips towards the center of the lips, puckering them.

The incisive muscles are  innervated by the facial nerve (VII) and are supplied with blood by the facial artery.