Till- TWGEMINAL .VA'ATA' 971 



alveolar (dental) artery, wliirh lies in front of the nerve, and it runs down \van Is and 

 forwards through the rannis and the body of tile mandible (lig. 7(1.'!)- At the mental 

 foramen it divides into two parts, one of which, the inintn! iiti'rt, passes out through 

 the mental foramen, the other, c nionly called the /W/X//T lironrli, continues for- 

 wards in the canal, and supplies, through the inferior dental plexus, the canine and 

 incisor teeth and the corresjMmding regions of the gums. 



Branches. 'I'he branches of the inferior alveolar (dental) nerve are the mylo- 

 hyoid. branches forming the inferior dental plexus, and the mental branch. 



The mylo-hyoid branch is given off immediately before the inferior alveolar 

 (dental) nerve enters t he mandibular (inferior dental) canal. It pierces I he lower and 

 back part of thespheno-maiidibular ligament and runs downwards and forwards in the 

 mylo-hyoid groove between the inaudible on the outer side, and the internal ptcry- 

 goid muscle and the outer surface of the submaxillary gland on the inner side. In 

 the anterior part of the digastric triangle it is continued forwards between the an- 

 terior part of the .submaxillary gland and the mylohyoideus, and it breaks up into 

 branches which supply the mylo-hyoideus and the anterior belly of the digastric 

 (fig. 703). 



The inferior dental plexus is formed by a series of branches which communicate 

 with one another within the bone, giving rise to a fine network. From this plexus 

 two sets of branches are given off: the inferior dental branches, corresponding in 

 number to the roots of the teeth, enter the minute foramina at the apices of the roots 

 and end in the pulp; the second set, the inferior gingival branches, supply the gun is. 



The mental nerve is a nerve of considerable size which emerges through the mental 

 foramen (fig. 703). It communicates, near its exit from the bone, with branches of 

 the facial nerve, and then divides into three branches. The smallest branch, turning 

 downwards, divides into several twigs, the mental branches, which supply the chin. 

 The other two, inferior labial branches, pass upwards, diverging as they ascend, and 

 divide into a number of twigs. The stoutest twigs ramify to the mucous mem- 

 brane which lines the lower lip. Other twigs are distributed to the integument and 

 fascia of the lip and chin. 



The Auriculo-temporal Nerve usually arises from the posterior portion of the 

 mandibular nerve by two roots which embrace the middle meningeal artery and unite 

 behind it to form the trunk of the nerve. The trunk passes backwards on the inner 

 aspect of the pterygoideus externus, and between the spheno-mandibular ligament 

 and the temporo-mandibular articulation, lying in close relation with the capsule of 

 the joint. Behind the joint it enters the upper part of the parotid gland, through 

 which it turns upwards and outwards. It emerges from the upper end of the gland, 

 crosses the root of the zygoma close to the posterior border of the superficial temporal 

 artery, and divides into auricular and temporal terminal branches at the level of the 

 tragus of the pinna (fig. 703). 



Communications. (a) Each of the two roots of the nerve receives a com- 

 munication from the otic ganglion containing fibres derived from the glosso-pharyn- 

 geal nerve. These fibres have passed through the tympanic plexus and the small 

 superficial petrosal nerve. 



(b) Communicating filaments pass from the auriculo-temporal nerve to the tem- 

 poro-facial branch of the facial nerve. 



(c). Filaments of connection with the sympathetic plexus on the internal max- 

 illary artery. 



(</) A communication to the inferior alveolar (dental) nerve. 



Branches, -(a) An articular branch to the temporo-mandibular joint, given 

 off as the nerve lies on the inner side of the capsule. 



(b) Branches to the external auditory meatus. Two branches, as a rule, are 

 given off in the parotid gland. They enter the meatus by passing between the 

 cartilage and the bone and supply the upper part of the meatus. the membrana 

 tympani by a fine branch, and occasionally the lower branch gives twigs to the skin of 

 the lobule. 



(e) Parotid branches are distributed to the substance of the parotid gland. 

 They spring either directly from the nerve or from the communicating branches to 

 the facial nerve, and they contain fibres derived from the glosso-pharyngeal nerve 

 which pass successively through its tympanic branch, the tympanic plexus, the 

 small superficial petrosal nerve, the otic ganglion, and through the communicating 

 twigs from the otic ganglion to the roots of the auriculo-temporal nerve. 



