Depressor labii inferioris muscle

The depressor labii inferioris (or quadratus labii inferioris) is a facial muscle that helps lower the bottom lip.

Structure
This muscle arises from the oblique line of the mandible, and inserts on the skin of the lower lip, blending in with the orbicularis oris muscle. At its origin, depressor labii is continuous with the fibers of the platysma muscle. Much yellow fat is intermingled with the fibers of this muscle.

Innervation
The depressor labii inferioris is innervated by the facial nerve.

Actions
This muscle helps to depress the lower lip.