The frontal belly of epicranius muscle (also known as the frontalis muscle), with assistance from the occipital belly, pulls the scalp back so that the eyebrows are lifted and the forehead can wrinkle. The epicranius muscle is a wide musculofibrous layer that wraps around one entire side of the vertex of the skull, from the occipital bone to the eyebrow. It’s made up of two muscles: the occipitalis and the frontalis.
The frontalis muscle takes on a thin, quadrilateral form. This muscle is wider than the occipitalis and its fibers are lighter in color and longer. There are no bony attachments. The medial fibers are connected with those of the Procerus; the corrugator and the orbicularis oculi mix with its immediate fibers. Its lateral fibers also mix with the latter muscle over the zygomatic process of the frontal bone.
At these attachments, the fibers move up and join the galea aponeurotica beneath the coronal suture. The medial margins of the frontales move together for a while above the root of the nose; however, between the occipitales there is a significant, though changing interval taken up by the galea aponeurotica.