The galeal aponeurosis encloses the frontalis muscle with a thin superficial layer over the muscle, and a deeper well-defined layer beneath the muscle. This deeper layer is firmly attached to the supraorbital margin, contributing to the arcus marginalis. Laterally, the galea conceptually continues as the superficial temporal fascia. Posteriorly, the galea continues as the occipitalis muscle. The 2 bellies of the occipitalis take their origin from the periosteum and bone of the superior nuchal line of the mastoid portion of the temporal bone and insert into the galea aponeurosis.
Innervation is by the posterior auricular branch of the facial nerve.
The paired corrugator superciliaris muscles arise from the frontal bone near the superomedial orbital rim, anteriorly and slightly cephalad to the trochlea. The muscle runs superolaterally through the fibers of orbicularis oculi and frontalis before inserting into the medial eyebrow skin. The corrugator muscle is a brow depressor, pulling the brow medially and inferiorly, producing vertical glabellar folds. Innervation is from terminal branches of the frontal branch of the facial nerve. The flat, thin procerus muscle takes origin from the nasal bone and inserts into the glabella and lower mid forehead.