THE MANDIBULAR NERVE 939 



(ii) The anterior superior alveolar (dental) nerve is the largest of the superior alveolar 

 nerves. It is given off by the infra-orbital nerve in the anterior part of the infra-orbital canal, 

 and passes downward in a bony canal in the anterior wall of the maxilla. After uniting with 

 the other alveolar nerves to form the superior dental plexus, it supplies the canines and the 

 incisors and gives branches to the mucous membrane of the maxillary sinus and the gums (fig. 

 735). It also gives off a nasal branch which enters the nasal fossa through a small foramen, and 

 supplies the mucous membrane of the anterior part of the inferior meatus and the adjacent 

 part of the floor of the nasal cavity. 



(iii) The superior dental plexus is formed in the bony alveolar canals by the three superior 

 alveolar nerves. It is convex downward and anastomoses across the mid-line with the corre- 

 sponding plexus of the other side (fig. 735). From it arise the superior dental branches supply- 

 ing the superior canines and incisors, superior gingival branches supplying the gums, and also 

 branches to the mucous membrane of the maxillary sinus and to the bone. On the plexus are 

 two gangliform enlargements, one, called the ganglion of Valentine, situated at the junction of 

 the middle and the posterior branches, and the other, called the ganglion of Bochdalek, at the 

 junction of the middle and anterior branches. 



(d) The terminal branches of the maxillary nerve are the inferior palpebral, 

 the external and internal nasal (nasal), and the superior labial. 



The inferior palpebral branches, usually two, pass upward and supply sensory fibres to all 

 the skin and conjimctiva of the lower eyelid (fig. 740). 



The external nasal branches pass medialward under cover of the levator labii superioris 

 (quadratus), and supply the skin of the posterior part of the lateral aspect of the nose. 



The internal nasal branches pass dowTiward and medialward under the lateral waU of the 

 aose, and then turn upward to supply the skin of the vestibule of the nose. 



The superior labial branches, three or four in number, as a rule are larger than the palpebral 

 and nasal branches. They pass downward to supply the skin and mucous membrane of the 

 upper hp and the neighbouring part of the cheek. 



(3) The Mandibular Nerve or Third Division of the Trigeminus 



The mandibular division is the largest of the three divisions of the trigeminus 

 (figs. 736 and 740). As a nerve, it is usually described as formed by the union of 

 two distinct nerves, namely, the entire masticator nerve and the large bundle 

 of sensory fibres derived from the semilunar (Gasserian) ganglion which pass 

 peripherally as the third division of the trigeminus. These two nerves remain 

 separate until they pass through the foramen ovale and then unite immediately 

 outside the skull to form a large trunk which almost directly after its formation 

 divides into a small anterior and a larger posterior portion. The trunk is situated 

 between the pterygoideus externus, laterally, and the otic ganglion and the 

 tensor palati medialty. In front of it is the posterior border of the pterygoideus 

 internus, and behind it, the middle meningeal artery. Two branches arise from 

 the trunk of the nerve before its division, namely, the spinous (recurrent) nerve 

 and the nerve to the pterygoideus internus. 



The spinous (recurrent) nerve, after receiving a vasomotor filament from the otic ganghon, 

 enters the cranium through the foramen spinosum, accompanying the middle meningeal artery, 

 and divides into an anterior and a posterior branch. The anterior branch communicates with 

 the meningeal branch of the maxillary division of the trigeminus, furnishes filaments to the 

 dura mater, and ends in the osseous substance of the great wing of the sphenoid. The posterior 

 branch traverses the petrosquamous suture and ends in the lining membrane of the mastoid 

 ceUs. 



The fibres going to form the nerve to the internal pterygoid muscle are almost wholly motor 

 fibres and therefore comprise a branch of the masticator nerve and are described as such under 

 the description of the masticator (fig. 737). 



The anterior portion of the mendibular nerve is smaller than the posterior and 

 is chiefly composed of motor fibres which form branches of the masticator nerve 

 and supply the muscles of mastication, the temporalis, masseter, and pteryg- 

 oideus externus. Practically all of the sensorj^ fibres of the anterior portion (fibres 

 of the mandibular nerve proper) form the buccinator (long buccal) nerve. The 

 latter is accompanied, in the first part of its course, by a small strand of motor or 

 masticator fibres which leaves it to end in the anterior part of the temporal 

 muscle. 



The buccinator (long buccal) nerve, entirely sensory, passes between the two heads of the 

 external pterygoid muscle and runs downward and forward under cover of or through the ante- 

 rior fibres of the temporalis to the cheek (fig. 736). As it passes forward it emerges fromimder 

 cover of the anterior border of the masseter and hes on the superficial sm-face of the buccinator, 

 where it interlaces with the buccal branches of the facial nerve and gives off filaments to supply 

 the superjacent skin; finally it pierces the buccinator and suppUes the mucous membrane on its 



