THE TRIGEMINAL NERVE 75 



external ear. The full distribution of the nerve includes a 

 strip of skin on the side of the head (Fig. 40), the skin of 

 the upper and anterior part of the external ear, and the skin 

 which lines the external acoustic meatus and the lateral 

 aspect of the tympanic membrane. 



2. The Buccinator (Long Buccal) Nerve supplies the skin 

 of the cheek behind the area innervated by the infra-orbital 

 nerve (Fig. 40). Many of its branches pierce the substance 

 of the cheek and supply the mucous membrane. When the 

 buccinator nerve is paralysed, portions of food tend to remain 

 lodged in the grooves between the cheek and the gums. 

 This is due to anaesthesia of the mucous membrane and not 

 to paralysis of the buccinator muscle, which is supplied by 

 the facial nerve (p. 82). 



3. The Inferior Alveolar (Dental) Nerve enters the 

 mandibular canal and supplies all the teeth of the lower 

 jaw. Its terminal branch, termed the mental nerve -, emerges 

 on the outer surface of the mandible through the mental 

 foramen and supplies the skin of the lower lip, the chin and 

 adjoining areas and the mucous membrane of the lower lip 

 (Fig. 40). 



4. The Lingual Nerve descends under cover of the ramus 

 of the mandible and passes forwards deep to the body of the 

 bone to enter the submaxillary region and reach the tongue 

 (Fig. 49). It supplies the mucous membrane of the floor of 

 the mouth and the anterior two-thirds of the tongue with 

 ordinary sensation. When a spatula is introduced into the 

 mouth, no unpleasant sensations are aroused as long as the 

 instrument is in contact with the area supplied by the 

 lingual nerve, but if it touches the posterior third or the 

 posterior part of the middle third, for the nerves supplying 

 adjoining areas overlap one another in their distribution 

 the glosso-pharyngeal nerve is stimulated and the pharyngeal 

 reflex is set up. 



In the first part of its course, the lingual nerve is joined by 

 the chorda tympani (p. 84), through which it supplies taste 



