Frontalis muscle

The cutaneous muscles of the head are all animated by the facial nerve (VII). These muscles act on the skin of the head, the cartilages of the nose or of the external ear. Besides their particular function (protection of the eye, mastication, etc.), they participate actively to the expression of feelings and determine the particular physionomy of the individual. They are sorted in three sub-groups: cutaneous muscles of the skull, cutaneous muscles of the face, and cutaneous muscles of the ear. 

Less developed in domestic Mammals than in Men, these muscles are sometimes considered as subdivisions of the same epicranial muscle (M. epicranius).

In Men, they are united by a broad epicranial aponeurosis (Galea aponeurotica, s. aponeurosis epicranialis) that covers the whole cranial vault, and whose edges they extend.

Besides a few lateral beams, near the temporal fossa (M. temporoparietalis), they constitute on each side two broad and thin muscular sheets located one on the occipital squama and the other on the forehead. These two formations are considered in the N.A. as two heads (venter occipitalis, venter frontalis) of a single occipitofrontal muscle (M. occipitofrontalis), turned digastric by the aposition of the epicranial aponeursis. This conception is hardly sustainable in compared anatomy and it is better described as an occipital muscle (M.occipitalis) inserted on the upper curved line of the occipital bone and a frontal muscle (M. frontalis) attached on the frontal bone, above the eyebrow.

In Carnivorous, both muscles are present; they are weak in Dogs but thick in Cats.

In Ungulates, the occipital muscle is missing.

In Rabbits, this muscle is very broad, extended from the interauricular region to the base of the nose; but it is so thin, light and adherent to the skin that it often goes unnoticed.

The cutaneous muscles of the skull get their motor innervation from the facial nerve (VII); the occipital by the caudal auricular branch and the frontal by the auriculopalpebral branch.