Corrugator Supercilii muscle
The Corrugator Supercilii is a small, narrow, pyramidal muscle found on the medial end of the eyebrow, beneath the Frontalis and just above the orbicularis oculi. It arises from the medial end of the superciliary arch, and its fibers pass upward and lateralward, between the palpebral and orbital portions of the Orbicularis oculi, and are inserted into the deep surface of the skin, above the middle of the orbital arch.
This muscle draws the eyebrow downward and medialward and produce the vertical wrinkles found on the forehead. It is referred to as the “frowning” muscle and may be regarded as the principal muscle in the expression of suffering. The muscle also contracts to prevent high sun glare, pulling the eyebrows toward the bridge of the nose, making a roof over the area above the middle corner of the eye and typical forehead furrows.
The corrugator supercilii is sometimes surgically cut or paralyzed with botulinum toxin to treat some types of migraine or for aesthetic reasons.
Image Caption: Corrugator Supercilii muscle. Wikipedia