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82 ANAT031Y.

importance and size only to the lower maxilla. When articulated they
form the bony base of the entire central portion of the face. Each one
assists in forming three cavities—first, part of the floor and the infra
and internal borders of the orbit ; second, part of the sides and floor of
the nasal chamber ; third, it contributes largely to form the roof or hard
palate of the mouth. It also assists in the formation of the zygomatic
and spheno-maxillary fossae and the spheno-maxillary and pterygo-
maxillary fissures.
Its body forms the walls of the maxillary sinus (antrum Highmori-
anum). It presents for examination a body, four surfaces, the orbital, the
proximal or nasal, the lateral or facial, and posterior or zygomatic ; and
four processes, the nasal, the malar, the palatal, and the alveolar.
The Body (Fig. 34) may be compared to a ve;y irregular triangular
Fig. 34.
Outer Surface.

TCNDO OeUL

PosteriorDentat Cunaia

Incisive fossa
xil'uru Tuleros'itu,

Bicusjiids. -Z^"'
Left Superior Maxillary I?one, outer surface.
pyramid, the base being the proximal surface and the apex under the
malar process.
The Orbital Surface is a triangular plate, smooth and slightly concave,
constituting the greater part of the floor of the orbit.
The LifWiorbital Canal runs forward from the posterior border as a
groove, which at the centre dips or is covered by the orbital floor, and
makes its exit just above the centre of the facial surface, at the infra-
orbital foramen. It transmits the infraorbital vessels and nerve. A
branch of the infraorbital canal passes down the anterior wall of the
maxillary sinus and transmits the anterior dental nerve and vessels.