THE PALATE BONE. 



205 



Spheno-maxillary 

 fosFa 



Sphenoida 

 process 



Orbital surface 



Orbital process 



Spheno-pala 

 tine notch 



prolongation. The inner surface, looking towards the nasal cavity, is free and 

 smooth. It is crossed below the middle by a ridge, the ijiferior turbinate cresf^ for 

 the posterior attachment of the inferior turbinate bone. Nearly on a level with the 

 base of the notch is another ridge faintly marked behind it ; this is the supe7'ior 

 turbinate cresf^ for the middle turbinate bone of the ethmoid. A small part of the 

 top of the vertical plate looks into the superior meatus. The pyramidal process, 

 or tuberosity, is the only solid part of the bone. It projects backward and some- 

 what outward from the lower part of the vertical plate. A smooth, hollowed, 

 triangular surface fits into the space left between the pterygoid plates, completing 

 the floor of the pterygoid fossa ; on one side of this is a groove for the front of the 

 internal pterygoid plate and on the other a rough surface for that of the outer. 

 Thus, through the palate bone, the pterygoids support the back of the upper jaw. 

 The outer side of the process rests against the tuberosity of the maxilla in front of 

 the tip of the external ptervgoid plate. The orbital process, is the anterior of the 

 two processes above the vertical plate, the larger and higher, so called because it 

 forms a small part of the fioor of the orbit near its apex on the inner side. This 

 little surface, on the outer side of the process, is triangular, one edge articulating 

 with the upper jaw and one with the os planum, the hind edge being free. Another 

 smooth surface looks outward and backward towards the spheno-maxillary fossa. 

 It is separated from the preceding surface 



by an angle. Three other surfaces rest f^'c. 230. 



against other bones. An antero-inferior 

 one joins the maxilla, sometimes helping 

 to close the antrum ; an anterior one 

 touches the ethmoid, bounding part of a 

 cell ■; and a small one, just at the top of 

 the notch, touches the sphenoidal spongy 

 bone. The posterior or sphenoidal 

 process has a narrow upper surface, 

 which, joining the sphenoidal spongy 

 bone near the base of the internal ptery- 

 goid plate, completes the ptery go -palatine 

 canal. This surface reaches the edge of 

 the vomer. The internal surface, slant- Tuberosity 

 ing a little downw^ard, is free, looking into 

 the nasal fossa. The outer surface is di- 

 vided by a vertical ridge into an anterior 

 part, free and smooth, looking into the spheno-maxillary fossa, and a scale-like pos- 

 terior portion which rests against the external pterygoid plate. 



The Spheno-Maxillary Fdssa. — When the palate bone is applied to the 

 sphenoid and the maxilla, the spheno-palatine foramen forms a window between the 

 nasal chamber and a litde hollow, the spheno-maxillary fossa, just below and behind 

 the apex of the orbit. The posterior wall of this space, formed by the smooth sur- 

 face of the sphenoid above the pterygoid plates, is pierced by th.Q fora?nen rotiindum 

 and the Vidian cayial. Below, it narrows funnel-like into \h^ posterior palatine canal. 



Articulations. — The palate bone articulates with its fellow, the superior max- 

 illary, sphenoid, ethmoid, vomer, and inferior turbinate bones. 



Development. — Ossification begins from a single centre appearing in mem- 

 brane near the end of the second foetal month at about the junction of the vertical 

 and horizontal plates. It is very delicate throughout foetal life, but the posterior 

 free edge of the palate is very early much denser. Originally the horizontal plate is 

 larger than the vertical one ; at birth they are about equal. 



THE VOMER. 



The vomer^ is a thin, irregularly quadrilateral plate, forming the back and lower 



part of the nasal septum. The superior border expands laterally into two wings, or 



alee, which articulate with the under surface of the body of the sphenoid, and enclose 



a medium groove for the rostrum. Laterally, the wings fit under the vaginal pro 



^ Crista turbinalis. - Crista ethmoidalis. ^ Vomer. 



Maxillary 



surface 



.-vntrum 



Post, pala- 

 tine canal 



For sup. 

 maxillary 



Right palate bone, outer aspect. 



