It's produced mainly by the corrugator muscle, which lowers & pulls together the eyebrows
Many branches of the STN pass through the corrugator supercilii at the origin 
area of .... should be mainly excised from the lateral upper side of the lower 
eyelid and the .... eyebrow lift, or forehead lift should be performed together in 
many cases,... [DOC] [TLE] Eyebrows, Eyelids, and Face: Structure and Function | Ento Key [PAR] Jul 11, 2016 ... Eyebrow cilia are directed at different angles in the upper and lower eyebrow.