38 PRACTICAL ANATOMY. 



anterior border is rounded, and forms part of the orbital 

 ridge ; its posterior border is rough, and articulates, 

 behind the frontal process, with the frontal ; lower down, 

 with the great wing of the sphenoid; the inner third 

 articulates with the superior maxillary. Just external to 

 its articulation with the superior maxillary is a smooth, 

 non-articular surface, which enters into the formation of 

 the spheno-maxillary fissure. The maxillary process is 

 a rough, trilateral surface, which articulates with the 

 superior maxillary bone. The zygomatic process is 

 strong, and serrated for articulation with the extremity 

 of the zygoma. The inferior border of the malar bone 

 is on a line with the zygoma. It develops from one 

 centre, which appears about the second month. 



THE SUPERIOR MAXILLARY BONE. 



The superior maxillary are two triangular bones 

 forming the upper jaw and the greater part of the 

 osseous structure of the face. Each bone articulates 

 with nine bones, the frontal, ethmoid, nasal, malar, 

 lachrymal, vomer, inferior turbinated, palate, and with 

 its fellow, with which its alveolar process forms an arch, 

 the superior dental, in which the teeth are placed. Each 

 bone assists in the formation of three cavities, the 

 orbital, nasal, and buccal; two fossae, the spheno- 

 maxillary and the zygomatic; and two fissures, the 

 pterygo-maxillary and the spheno-maxillary. It pre- 

 sents for examination a body and four processes, nasal, 

 malar, palatine, and alveolar. In the adult the body 

 is cuboidal, hollow, and forms an air sinus, known 

 as the antrum of Highmore, which begins to develop 

 about the fifth year. The superior surface of the body 

 is smooth, triangular, and presents a groove, the infra- 

 orbital, which begins at the posterior border and curve 



