THE GLOSSOPHARYXGEAL NERVE 



907 



Auricular 



Tympanic 



four filaments to the upper part of the medulla oblongata, in the groove between 

 the olive and the inferior peduncle. 



The sensory fibers arise from the cells of the superior and petrous ganglia, which 

 are situated on the trunk of the nerve, and will be presently described. When 

 traced into the medulla, 

 some of the sensory fibers, 

 probably sympathetic af- 

 ferent, end by arborizing 

 of the 

 a nucleus 



which lies beneath the ala 

 cinerea in the lower part of 

 the rhomboid fossa. Many 

 of the fibers, probably the 

 taste fibers, contribute to 

 form a strand, named the 

 fasciculus solitarius, which 

 descends in the medulla 

 oblongata. Associated with 

 this strand are numerous 

 nerve cells, and around 

 these the fibers of the 

 fasciculus end. The 



so- 



Pharyngeal 



Laryngeal 



FIG. 791. Plan of upper portions of glossopharyngeal, vagus, and 

 accessory nerves. 



matic sensory fibers, few in 

 number, are said to join 

 the spinal tract of the tri- 

 geminal nerve. 



The somatic motor fibers 

 spring from the cells of the 

 nucleus ambiguus, which lies some distance from the surface of the rhomboid fossa 

 in the lateral part of the medulla and is continuous below with the anterior gray 

 column of the medulla spinalis. From this nucleus the fibers are first directed 

 backward, and then they bend forward and lateralward to join the fibers of the 

 sensory root. The nucleus ambiguus gives origin to the motor branches of the 

 glossopharyngeal and vagus nerves, and to the cranial part of the accessory nerve. 



The sympathetic efferent fibers from the nucleus beneath the ala cinerea, the dorsal 

 nucleus, are probably both preganglionic motor fibers and preganglionic secretory 

 fibers of the sympathetic system. The secretory fibers pass to the otic ganglion 

 and from it secondary neurons are distributed to the parotid gland. Some authors 

 describe these fibers as arising from a distinct nucleus the inferior salivatory 

 nucleus, which lies near the dorsal nucleus. 



From the medulla oblongata, the glossopharyngeal nerve passes lateralward 

 across the flocculus, and leaves the skull through the central part of the jugular 

 foramen, in a separate sheath of the dura mater, lateral to and in front of the vagus 

 and accessory nerves (Fig. 792). In its passage through the jugular foramen, 

 it grooves the lower border of the petrous part of the temporal bone; and, at its 

 exit from the skull, passes forward between the internal jugular vein and internal 

 carotid artery; it descends in front of the latter vessel, and beneath the styloid 

 process and the muscles connected with it, to the lower border of the Stylo- 

 pharyngeus. It then curves forward, forming an arch on the side of the neck 

 and lying upon the Stylopharyngeus and Constrictor pharyngis medius. Thence 

 it passes under cover of the Hyoglossus, and is finally distributed to the palatine 

 tonsil, the mucous membrane of the fauces and base of the tongue, and the 

 mucous glands of the mouth. 



