THE NINTH OR GLOSSOPHARYNGEAL NERVE 1Q05 



Its (apparent) superficial origin is by three or four filaments, closely connected, 

 from the upper part of the medulla oblongata, in the dorsolateral groove (Fig. 743). 



The central connections are described on page 882. The small motor component 

 arises from cells in the nucleus ambiguus. The real origin of the sensor fibres 

 of the glossopharyngeal must be looked for in the jugular and petrosal ganglia 

 which are developed from the neural crest. 



From its superficial origin it passes outward across the flocculus, and leaves 

 the skull at the central part of the jugular foramen, in a separate sheath of the 

 dura external to and in front of the vagus and spinal accessory nerves (Fig. 744). 

 In its passage through the jugular foramen it grooves 

 the lower border of the petrous portion of the temporal 

 bone, and at its exit from the skull passes forward 

 between the jugular vein and internal carotid artery," 

 and descends ventrad of the latter vessel, and beneath 

 the styloid process of the temporal bone and the 

 muscles connected with it, to the lower border of the 

 Stylopharyngeus muscle. The nerve now curves in- 

 ward, forming an arch on the side of the neck, and 

 lying upon the Stvlopharyngeus muscle and the Middle 

 constrictor of the pharynx. It then passes beneath 



the Hyoglossus muscle, and is finally distributed to eaS^S^^SSS^ 

 the mucous membrane of the fauces and base of the and eleventh cramai nerves. 

 tongue, and the mucous glands of the mouth and tonsil. 



In passing through the jugular foramen the nerve presents, in succession, two 

 gangliform enlargements. The superior and smaller is called the jugular ganglion; 

 the inferior and larger, the petrous ganglion or the ganglion of Andersch. 



The superior or jugular ganglion (ganglion superius) is situated in the upper 

 part of the groove in which the nerve is lodged during its passage through the 

 jugular foramen. It is of very small size, and involves only part of the trunk of 

 the nerve. It is usually regarded as a detached portion from the lower ganglion. 



The inferior or petrous ganglion (ganglion inferius) is situated in a depression 

 in the lower border of the petrous portion of the temporal bone; it is larger than 

 the superior ganglion and involves the whole of the fibres of the nerve. From 

 this ganglion arise those filaments which connect the glossopharyngeal with the 

 vagus and sympathetic nerves. 



Branches of Communication. The branches of communication are with the 

 symathetic, and facial. 



The branches to the vagus are two filaments, arising from the petrous ganglion, 

 one of which passes to the auricular branch of the vagus, and one to the upper 

 ganglion of the vagus. 



The petrous ganglion is connected by a filament with the superior cervical 

 ganglion. 



The branch of communication with the facial perforates the posterior belly of 

 the Digastric muscle. It arises from the trunk of the nerve below the petrous 

 ganglion, and joins the facial just after its exit from the stylomastoid foramen. 



Branches of Distribution. The branches of distribution are the tympanic, 

 carotid, pharyngeal, muscular, tonsillar, and lingual. 



The Tympanic Branch or Jacobson's Nerve (n. tympanicus) arises from the petrous 

 ganglion, and enters a small bony canal in the lower surface of the petrous portion 

 of the temporal bone, the lower opening of which is situated on the bony ridge 

 which separates the carotid canal from the jugular fossa. It ascends to the tym- 

 panum, enters that cavity by an aperture in its floor close to the inner wall, and 

 divides into branches which are contained in grooves upon the surface of thv? 

 promontory. These branches form a tympanic plexus (plexus tympanicus}. This 



