THE FIFTH, TRIGEMINAL, OR TRIFACIAL NERVE 681 



plexus and ganglia come chiefly from the branches of the sphenopalatine nerve and the nerve of 

 the pterygoid canal. Interspersed in these arc several minute ganglia and one or more larger 

 ones. The nerve of the pterygoid canal or Vidian nerve (X. canalis pterygoidei) is formed by 

 the union of sympathetic fibers with the superficial petrosal l)ranch of the facial nerve. It passes 

 forward at first between the Eustachian tube and the sphenoid bone, enters the canal between 

 the pterygoid bone and process, and joins the posterior part of the plexus. It is probable that 

 it furnishes the motor fibers to the levator palati and palatinus muscles. Efferent filaments go to 

 the periorbita and the ophthalmic vessels, and others accompany the branches of the maxil- 

 lary nerve, around which they have a plexiform arrangement. 



3. The infraorbital nerve (N. infraorbitalis) is the continuation of the maxillary 

 trunk. It traverses the infraorbital canal, emerges through the infraorbital fora- 

 men, and divides into nasal and superior labial branches. Along its course it gives 

 off superior alveolar or dental branches (Rami alveolares maxillse), which supply 

 the teeth, alveolar periosteinn, and gums. 



The delicate posterior alveolar branches are given off in the pterygo-palatine fossa, pass 

 through small foramina in the tuber maxillare, and supply the posterior molar teeth and the 

 maxillary sinus. The middle alveolar branches are given off in the infraorbital canal, and consti- 

 tute the chief nerve-supply to the cheek teeth and the maxillary sinus. The anterior or incisor 

 branch runs forward in the anterior alveolar or incisor canal and supplies branches to the canine 

 and incisor teeth. The foregoing unite with each other to form the superior dental plexus, 

 from which the dental and gingival branches are given off. 



The external nasal branches (Rami nasales externi), two or three in number, 

 accompany the levator lal)ii superioris proprius and ramify in the dorsum nasi and 

 the nasal diverticulum. 



The large anterior nasal branch (Ramus nasalis anterior) passes over the nasal 

 process of the premaxilla under cover of the dilatator naris inferior, gives branches 

 to the nasal mucous mem])rane. and terminates in the skin of the upper lip. 



The superior labial branch (Ramus labialis dorsalis) is the largest of the termi- 

 nals of the infraorbital nerve. It pass(^s downward and forward under the levator 

 nasolabialis and, after supplying the skin of the anterior part of the cheek, forms a 

 rich terminal ramification in the skin and mucous membrane of the upper lip. It 

 anastomoses with the superior liuccal branch of the facial nerve. 



III. The mandibular nerve (N. mandibularis), also termed the inferior maxil- 

 larj^ branch, is formed by the union of two roots; of these the large sensory root 

 comes from the semilunar ganglion, and the small motor root is the pars minor of 

 the trigeminus. It emerges from the cranium through the oval notch of the fora- 

 men lacerum, between the temporal wing of the sphenoid bone and the muscular 

 process of the petrous temporal, and gives off the following branches: 



1. The masseteric nerve (N. massetericus) (Figs. 437, 515) passes outward 

 through the sigmoid notch of the mandible and enters the deep face of the masseter 

 muscle, in which it ramifies. 



2. The deep temporal nerves (Nn. temporales profundi) (Fig. 437), two 

 or three in numlier, arise by a common trunk with the masseteric. They 

 supply the temporal muscle. 



3. The buccinator nerve (N. buccinatorius) passes obliquely forward through 

 the anterior part of the external pterygoid muscle, then between the internal 

 pterygoid and the tuber maxillare (Fig. 514). It continues forward in the sub- 

 mucous tissue of the cheek along the lower border of the buccinator and divides 

 into branches which ramify in the mucous membrane and glands of the lips in the 

 vicinity of the commissure. It supplies small branches to the external pterygoid 

 and temporal muscles and detaches numerous collateral twigs to the mucous mem- 

 brane of the cheek and to the buccal glands. It also communicates with the in- 

 ferior buccal branch of the facial nerve. 



4. The pterygoid nerve (N. pterygoideus) arises in common with the preceding, 

 passes forward on the guttural pouch, and divides into branches for the pterygoid 

 muscles (Fig. 515). 



The otic gangUon (G. oticum) is situated near the origin of the pterygoid and 



