THE PALATE BONES. 



151 



The pars horizontalis (horizontal part) has two surfaces and four borders. 

 As its name implies, it is horizontal in position, and forms the posterior third of 

 the hard palate. ' Its superior surface, which is smooth, is slightly concave from side 

 to side, and forms the floor of the posterior part of the nasal cavity. Its inferior 

 ! surface, rougher, is directed towards the mouth, and, near its posterior edge, often 

 displays a transverse ridge for the attachment of a part of the aponeurosis of the 

 tensor veli palatini muscle. The anterior border articulates by means of an irregular 

 suture with the posterior edge of the palatine process of the maxilla. The posterior 

 margin is free and concave from side to side ; by its sharp edge it furnishes 

 attachment to the aponeurosis of the soft palate. The medial border is upturned, 

 and when it articulates with its fellow of the opposite side it forms superiorly 

 a central crest continuous in front with the nasal crest of the maxilla; it 

 supports the posterior part of the inferior border of the vomer, and projecting 

 beyond the line of the posterior border forms the posterior nasal spine. The 

 lateral border fuses with the vertical part, forming with it a right angle. 

 The posterior extremity of this edge is grooved by the foramen palatinum 

 majus. 



Sphenoid 



Pter 



palatine 



Orbital process 

 Ethmoid 



Orbital surface 



For maxilla 



Orbital process 



Sphenoid 



Surface towards 

 maxillary sinus 



terygoid 

 Dr lateral 

 )terygoid 

 lamina 

 yramidal 

 process 



.rface for attach. Surface Pterygo-palatine sulcus 

 >f pterygoideus for maxilla 

 internus 



Maxillary 



Maxillary process 



process 



Nasal crest 



Horizontal 

 part 



Orbital surface 



Ethmoid 



Crista ethmoidalis 

 Spheno-palatine notch 



Crista 

 conchal is 



Sphenoidal 

 process 



Superior 

 meatus 



Middle meatus 



Inferior meatus 



Pterygoid fossa 



Pyramidal 

 process 



Posterior For medial 

 nasal spine pterygoid lamina 



B 



FIG. 160. RIGHT PALATE BONE. 

 A, As seen from the Lateral Side ; B, As viewed from the Medial Side. 



The pars perpendicularis (perpendicular part) is very much broader below 

 than above. Composed of thin bone, particularly at its superior part, it is liable 

 to be broken in the process of disarticulation, so that it is somewhat uncommon to 

 meet with a perfect specimen. It may be described as possessing two surfaces 

 and four borders. Its medial surface, which is directed towards the cavity of the 

 nose, is crossed horizontally, about its middle, by the crista conchalis (conchal crest) 

 with which the posterior end of the superior border of the inferior conchal bone 

 articulates ; above and below this, it enters into the formation of the lateral wall 

 of the middle and inferior meatuses of the nose, respectively. Near the superior 

 extremity of the perpendicular part, and below the processes which spring from it, 

 there is another ridge more or less parallel to that already described. This is the 

 crista ethmoidalis (ethmoidal crest), and with this the posterior extremity of the middle 

 concha articulates. The lateral surface, which forms the medial wall of the pterygo- 

 palatine fossa, is channelled by a vertical groove (sulcus pterygopalatinus), converted 

 into the pterygo -palatine canal by articulation with the maxilla. This canal, called 

 at its lower end the greater palatine foramen, transmits the posterior palatine nerve 

 and greater palatine vessels. Anteriorly the lateral surface projects forwards to a 

 variable extent, and helps to close in the maxillary sinus by its maxillary process. 

 The anterior border is a thin edge, of irregular outline, which articulates above with 

 the ethmoid, with the posterior edge of the maxillary process of the inferior conchal 

 bone about its middle, and below with the maxilla. The posterior border, thin above, 



