Anatomy of the Human head

Below the nasion the nasal bones, scantily covered by soft tissues, can be traced to their junction with the nasal cartilages, and on either side of the nasal bone the complete outline of the orbital margin can be made out. At the junction of the medial and intermediate thirds of the supraorbital margin the supraorbital notch, when present, can be felt; close to the medial end of the infraorbital margin is a little tubercle which serves as a guide to the position of the lacrimal sac. Below and lateral to the orbit, on either side, is the zygomatic bone forming the prominence of the cheek; its posterior margin is easily palpable, and on it just above the level of the lateral palpebral commissure is the zygomatic tubercle. A slight depression, about 1 cm. above this tubercle, indicates the position of the zygomaticofrontal suture. Directly below the orbit a considerable part of the anterior surface of the maxilla and the whole of its alveolar process can be palpated. The outline of the mandible can be recognized throughout practically its entire extent; in front of the tragus and below the zygomatic arch is the condyle, and from this the posterior border of the ramus can be followed to the angle; from the angle to the symphysis the lower rounded border of the mandible can be easily traced; the lower part of the anterior border of the ramus and the alveolar process can be made out without difficulty. In the receding angle below the chin is the hyoid bone, and the finger can be carried along the bone to the tip of the greater cornu, which is on a level with the angle of the mandible: the greater cornu is most readily appreciated by making pressure on one side, when the cornu of the opposite side will be rendered prominent and can be felt distinctly beneath the skin. Joints and Muscles.—The temporomandibular articulation is quite superficial, and is situated below the posterior end of the zygomatic arch, in front of the external acoustic meatus. Its position can be ascertained by defining the condyle of the mandible; when the mouth opens, the condyle advances out of the mandibular fossa on to the articular tubercle, and a depression is felt in the situation of the joint. The outlines of the muscles of the head and face cannot be traced on the surface except in the case of the Masseter and Temporalis. The muscles of the scalp are so thin that the outline of the bone is perceptible beneath them. Those of the face are small, covered by soft skin, and often by a considerable layer of fat, and their outlines are therefore concealed; they serve, however, to round off and smooth prominent borders, and to fill up what would otherwise be unsightly angular depressions. Thus the Orbicularis oculi rounds off the prominent margin of the orbit, and the Procerus fills in the sharp depression below the glabella. In like manner the labial muscles converging to the lips, and assisted by the superimposed fat, fill up the sunken hollow of the lower part of the face. When in action the facial muscles produce the various expressions, and in addition throw the skin into numerous folds and wrinkles. The Masseter imparts fulness to the hinder part of the cheek; if firmly contracted, as when the teeth are clenched, its quadrilateral outline is plainly visible; the anterior border forms a prominent vertical ridge, behind which is a considerable fulness especially marked at the lower part of the muscle. The Temporalis is fan-shaped and fills the temporal fossa, substituting for the concavity a somewhat convex swelling, the anterior part of which, on account of the absence of hair on the overlying skin, is more marked than the posterior, and stands out in strong relief when the muscle is in action.
FIG. 1194– Anterolateral view of head and neck. (See enlarged image) In the neck, the Platysma when contracted throws the skin into oblique ridges parallel with the fasciculi of the muscle. The Sternocleidomastoideus has the most important influence on the surface form of the neck (Figs. 1194, 1195). When the muscle is at rest its anterior border forms an oblique rounded edge ending below in the sharp outline of the sternal head; the posterior border is only distinct for about 2 or 3 cm. above the middle of the clavicle. During contraction, the sternal head stands out as a sharply defined ridge, while the clavicular head is flatter and less prominent; between the two heads is a slight depression: the fleshy middle portion of the muscle appears as an oblique elevation with a thick, rounded, anterior border, best marked in its lower part. The sternal heads of the two muscles are separated by a V-shaped depression, in which are the Sternohyoideus and Sternothyreoideus. Above the hyoid bone, near the middle line, the anterior belly of the Digastricus...

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