Anterior View (norma frontalis – fig. 314)
Viewed from in front the skull exhibits a somewhat oval outline, wider above than below. Its upper part is formed by the frontal bone and is smooth and convex. Its lower part, which forms the skeleton of the face, is very irregular and is interrupted by the orbits and the anterior bony aperture of the nose. Immediately above the medial part of each orbit the superciliary arch forms a rounded elevation, better marked in the male than in the female skull, and these two arches are connected by a median elevation,, termed the glabella. Below the glabella the skull recedes to the point where the nasal bones meet the frontal, forming the floor of a depression at the root of the nose which is named the nasion. Above the superciliary arch on each side the frontal eminence forms a slight rounded elevation. All these are bony landmarks which can be felt without difficulty in the living subject, and the glabella and nasion provide reference points for the surgeon in certain intracranial operations.
The anterior bony aperture of the nose is pear-shaped, wider below than above and bounded by the nasal bones and the maxilla. The two nasal bones articulate with each other in the median plane and both articulate Faith the frontal bone above. On each side the nasal bone articulates behind with the frontal process of the maxilla, but its lower border, to which the upper nasal cartilage is attached in the fresh specimen, is free and forms the upper boundary of the bony nasal aperture.
Much the largest part of the skeleton of the face is formed by the maxillae, and it is the growth of these bones which is responsible for the elongation of the face that occurs during childhood. It is only the anterior surface of the maxilla which is visible in the norma frontalis. Medially this surface presents the well-marked nasal notch, which forms the lower border and the adjoining part of the lateral border of the anterior bony aperture of the nose. A prominent, sharp projection marks the meeting of the two maxilla in the lower boundary of the aperture and is termed the anterior nasal spine. It can be identified in the lower border of the free part of the nasal septum in the living subject. About 1 cm below the infraorbital margin the maxilla is perforated by the infra-orbital foramen, which transmits the infra-orbital vessels and nerve; it lies on, or just lateral to, a vertical line passing through the supra-orbital foramen. The alveolar process of the maxilla, which provides the sockets for the maxillary teeth, can be examined most satisfactorily in the norma basalis. The zygomatic process of the maxilla is a short but substantial projection from the upper and lateral part of the anterior surface of the bone. Its oblique upper surface articulates with the zygomatic bone at the zygomaticomaxillary suture. Inferiorly it presents a free lower border, which meets the body of the bone above the first molar tooth, and can be palpated through the skin of the cheek or through the mucous membrane of the vestibule of the mouth. The frontal process of the maxilla ascends behind the nasal bone, forming the lower part of the medial margin of the orbital opening, and reaches the frontal bone. It will be examined again subsequently, both in the orbit and in the nose.
The prominence of the cheek below and lateral to the orbit is produced by the zygomatic bone. It is the convex lateral surface of the bone which can be examined both in the norma frontalis and in the norma lateralis. Its contributions to the margins of the orbital opening and its articulation with the maxilla have already been noted.
Particular features.-The glabella may show the remains of the frontal suture, which in about 9 per cent. of skulls extends upwards to the coronal suture. It indicates that the adult frontal bone is formed by the fusion of right and left halves, which ossify independently of each other. The medial part of the superciliary arch gives origin to the corrugator muscle. The nasal part of the frontal bone and the frontal process of the maxilla give origin to the orbital part of the orbicularis oculi muscle. Between these two areas the medial palpebral ligament is attached to the frontal process of the maxilla (fig. 384). The procerus muscle arises from the nasal bone near the median plane. The lower margin of the nasal bone usually presents a. small notch, converted into a foramen in the fresh specimen by the lateral cartilage of the nose. It transmits the external nasal nerve. In front of the orbicularis oculi the levator labii superioris alaque nasi (angular head of the quadratus labii superioris) takes origin from the frontal process of the maxilla. More laterally, the levator labii superioris (infra-orbital head of the quadratus labii superioris) arises from. the maxilla in the interval between the infra-orbital margin and the foramen of the same name.
The stout root of the canine tooth produces an elevation, termed the canine eminence, which separates the canine fossa on its lateral side from the incisive, fossa on its medial side. The levator anguli oris (m. caninus) arises from the canine fossa, while the incisive fossa wives origin to the compressor naris muscle (transverse part of the m. nasalis). Below these fossa the anterior surface of the maxilla gives origin to the depressor septi, the dilator naris (alar part of m. nasalis) and the incisive muscle of the upper lip.
The zygomatic bone is marked opposite the junction of the infra-orbital and lateral margins of the orbit by the small zygomaticofacial foramen, which transmits the nerve of the same name and a minute artery. The foramen, which is sometimes duplicated, opens laterally and downwards. Below the foramen the zygomatic bone gives origin to the zygomaticus minor muscle (zygomatic head of the m. quadratus labii superioris), and more laterally to the zygomaticus major muscle (m. zygomaticus).
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