Depressor anguli oris muscle

The depressor anguli oris (triangularis) is a facial muscle associated with frowning.
It originates from the mandible and inserts into the angle of the mouth.
The muscle is innervated by the marginal mandibular branch of the facial nerve and receives its blood supply from the facial artery.
Anatomy.
The depressor anguli oris arises from the oblique line of the mandible, whence its fibres converge, to be inserted, by a narrow fasciculus, into the angle of the mouth. At its origin it is continuous with the platysma, and at its insertion with the orbicularis oris and risorius; some of its fibers are directly continuous with those of the caninus, and others are occasionally found crossing from the muscle of one side to that of the other; these latter fibers constitute the transversus menti.
Function.
The depressor anguli oris is a muscle of facial expression. The muscle depresses the corner of the mouth which is associated with frowning.