Henry Gray (18251861). Anatomy of the Human Body. 1918.
The medial margins of the Frontales are joined together for some distance above the root of the nose; but between the Occipitales there is a considerable, though variable, interval, occupied by the galea aponeurotica.
The galea aponeurotica (epicranial aponeurosis) covers the upper part of the cranium; behind, it is attached, in the interval between its union with the Occipitales, to the external occipital protuberance and highest nuchal lines of the occipital bone; in front, it forms a short and narrow prolongation between its union with the Frontales. On either side it gives origin to the Auriculares anterior and superior; in this situation it loses its aponeurotic character, and is continued over the temporal fascia to the zygomatic arch as a layer of laminated areolar tissue. It is closely connected to the integument by the firm, dense, fibro-fatty layer which forms the superficial fascia of the scalp: it is attached to the pericranium by loose cellular tissue, which allows the aponeurosis, carrying with it the integument to move through a considerable distance.
Variations.Both Frontalis and Occipitalis vary considerably in size and in extent of attachment; either may be absent; fusion of Frontalis to skin has been noted.
Nerves.The Frontalis is supplied by the temporal branches of the facial nerve, and the Occipitalis by the posterior auricular branch of the same nerve.
Actions.The Frontales raise the eyebrows and the skin over the root of the nose, and at the same time draw the scalp forward, throwing the integument of the forehead into transverse wrinkles. The Occipitales draw the scalp backward. By bringing alternately into action the Frontales and Occipitales the entire scalp may be moved forward and backward. In the ordinary action of the muscles, the eyebrows are elevated, and at the same time the aponeurosis is fixed by the Occipitales, thus giving to the face the expression of surprise; if the action be exaggerated, the eyebrows are still further raised, and the skin of the forehead thrown into transverse wrinkles, as in the expression of fright or horror.
A thin muscular slip, the Transversus nuchæ, is present in a considerable proportion (25 per cent.) of cases; it arises from the external occipital protuberance or from the superior nuchal line, either superficial or deep to the Trapezius; it is frequently inserted with the Auricularis posterior, but may join the posterior edge of the Sternocleidomastoideus.
4b. The Muscles of the Eyelid
The muscles of the eyelids are:
Levator palpebræ superioris.
The Levator palpebræ superioris is described with the Anatomy of the Eye.
The Orbicularis oculi (Orbicularis palpebrarum) (Fig. 379)arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament. From this origin, the fibers are directed lateralward, forming a broad and thin layer, which occupies the eyelids or palpebræ, surrounds the circumference of the orbit, and spreads over the temple, and downward on the cheek. The palpebral portion of the muscle is thin and pale; it arises from the bifurcation of the medial palpebral ligament, forms a series of concentric curves, and is inserted into the lateral palpebral raphé. The orbital portion is thicker and of a reddish color; its fibers form a complete ellipse without interruption at the lateral palpebral commissure; the upper fibers of this portion blend with the Frontalis and Corrugator. The lacrimal part (Tensor tarsi) is a small, thin muscle, about 6 mm. in breadth and 12 mm. in length, situated behind the medial palpebral ligament and lacrimal sac (Fig. 379). It arises from the posterior crest and adjacent part of the orbital surface of the lacrimal bone, and passing behind the lacrimal sac, divides into two slips, upper and lower, which are inserted into the superior and inferior tarsi medial to the puncta lacrimalia; occasionally it is very indistinct.