Section 3. Anatomy of the maxillofacial system

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Chapter 6. Anatomical structure of the maxilla and mandible

The oral cavity and the facial region are functionally, anatomically, and topographically closely related. A substantial proportion of the anatomical area falls on the masticatory apparatus, which represents the initial part of the human digestive system. The remaining part is represented by the sense organs, organs of speech and upper respiratory system. The importance of these organs and systems for the functioning of the body as a whole and their connection with the maxillofacial area determines its features.

The bony skeleton of the face is represented by 6 paired and 2 unpaired bones:

Paired bones:

a) maxillary bones;

b) zygomatic bones;

c) palatine bones;

d) nasal bones;

e) lacrimal bones;

f) nasal conchae.

Unpaired bones:

a) mandible;

b) vomer.

All the listed bones, except the mandible, are connected and immobile to each other and to the base of the skull (fixed bones). The mandible is the only movable bone in the facial skeleton. This bone is connected to the base of the skull by the temporo-mandibular joint and, due to the peculiarities of its structure, moves in three planes.

The maxilla is paired, located in the upper anterior part of the facial skeleton. It belongs to the number of air-bearing bones since it contains a vast cavity lined with a mucous membrane — the maxillary sinus. In the bone there is a shaft and four processes (fig. 6.1).

Fig. 6.1. Maxilla: 1 — frontal process, 2 — lacrimal sulcus, 3 — orbital surface, 4 — infraorbital sulcus, 5 — suborbital margin, 6 — maxillary tubercle, 7 — infraorbital foramen, 8 — zygomatic process, 9 — alveolar foramina, 10 — canine fossa, 11 — alveolar elevations

The shaft of the maxilla, inside which the specified sinus lies, has four surfaces: upper or orbital, anterior, internal or nasal, posterior or infratemporal. The bone processes are as follows: frontal, zygomatic, alveolar and palatine.

The orbital surface is smooth, triangular in shape, slightly tilted forward, outward, and downward, forming the lower wall of the eye pit.

The posterior edge of the upper surface together with the parallel lower edge of the orbital surface of the large wings of the sphenoid bone forms the lower orbital fissure. In the middle of its extension, the lower wall of the slit has a groove, an infraorbital sulcus, which, going anteriorly, becomes deeper and gradually passes into the infraorbital canal, (in the sulcus and canal lie the infraorbital nerve, artery and veins). The canal delineates an arc and opens on the front surface of the shaft of the maxilla.

The nasal surface of the maxilla is more complex. In its upper-posterior corner there is a foramen — a scissure of the maxillary sinus leading to the maxillary sinus. Posteriorly from this opening, the rough nasal surface is connected by a suture to the perpendicular plate of palatine bone and bears a vertically running large palatine sulcus, which is a part of the walls of the large palatine canal.

From the upper edge of the nasal surface, at the point where it passes into the anterior, the frontal process is directed upwards. It has a medial (nasal) and lateral (facial) surface. The lateral surface is divided into anterior and posterior sections by the anterior lacrimal crest. The posterior section passes down into the lacrimal sulcus. It is bounded from the inside by the lacrimal margin, to which the lacrimal bone is attached, forming a lacrimal-maxillary suture with it. An ethmoidal crest runs from the medial surface from front to back.

The upper edge of the frontal process is notched and connects to the nasal part of the frontal bone in the fronto-maxillary suture. The anterior edge of the frontal process connects to the nasal bone in the naso-maxillary suture. The zygomatic process departs from the outer upper corner of the shaft of the maxilla.

The lower surface is rough and has two palatine sulci near its posterior end, which are separated from each other by small palatine spines (vessels and nerves lie in the sulci). Between both the right and left palatine processes, at the anterior edge, an incisive canal is formed. The incisive foramen of this canal may be located on one of the processes, in which case the incisive sulcus is located on the opposite process. The alveolar process, the development of which stands in connection with the development of teeth, departs from the lower edge of the shaft of bone downwards and delineates an arc directed by the nub forward and outward.

The anterior surface of the alveolar process, corresponding to the five anterior alveoli, has longitudinal alveolar elevations. Part of the alveolar process with the alveoli of the two anterior incisors represents a separate incisive bone in the fetus, which merges early with the alveolar process of the maxilla.

The nasal bone is paired, quadrangular, slightly elongated and convex anteriorly. The upper edge is connected to the nasal part of the frontal bone, the lateral edge is connected to the anterior edge of the frontal process of maxilla. The anterior surface of the bone is smooth and perforated with one or more holes (a track of the passage of blood vessels and nerves). The posterior surface is slightly concave and has an ethmoidal sulcus — a track of the anterior ethmoid nerve in it (fig. 6.2).