654 



TEXT-BOOK OF PHYSIOLOGY 



reflex actions which are highly essential to the life of the individual, e.g., 

 respiration, the heart-beat, blood-pressure, etc., all of which have been con- 

 sidered in foregoing pages. 



THE ELEVENTH NERVE. THE SPINAL ACCESSORY 



The eleventh cranial nerve, the spinal accessory, consists of peripherally 



coursing fibers which bring the nerve-cells 

 from which they arise into relation with 

 separate but functionally related muscles, 

 such as those entering into the formation 

 of the larynx. It consists of two por- 

 tions, the medullary or bulbar and the 

 spinal. 



Origin. The axons comprising the 

 medullary portion arise from a group of 

 nerve-cells in the extreme lower part of 

 the nucleus ambiguus, known as the nidus 

 laryngei. From this origin the axons 

 pass forward and outward to emerge from 

 the medulla just below and in series with 

 the roots of the vagus nerve. 



The axons comprising the spinal por- 

 tion have their origin in nerve-cells in 

 the lateral margin of the anterior horn 

 of the gray matter in the cervical portion 

 of the cord as far down as the fifth cer- , 

 vical vertebra. From this origin the 

 fibers pass to the surface of the cord to 

 emerge between the ventral and dorsal 

 roots in from six to eight filaments, after 

 which they unite from below upward to 

 form a distinct nerve. This enters the 

 cranial cavity through the foramen mag- 

 num, where it joins with the medullary 

 portion to form the common trunk, which 

 then passes forward to emerge from the 

 cranium through the jugular foramen. 

 (Fig. 269.) 



Distribution. After emerging from 

 the cranial cavity the nerve soon sepa- * 

 rates into two branches: 

 i. An internal or anastomotic branch, 

 consisting chiefly of filaments com- 

 ing from the medulla oblongata. It 

 soons enters the trunk of the vagus, 

 from which fibers pass through the 

 pharyngeal plexus to the superior 



and inferior constrictor muscles of the pharynx, to the palato-pharyngeus, 

 to the levator palati and azygos uvulae muscles (Beevor and Horsley) ; to 



FIG. 269. SPINAL ACCESSORY NERVE. 

 i. Trunk of the facial nerve. 2, 2. 

 Glosso- pharyngeal nerve. 3, j.Pneumo- 

 gastric. 4,4,4. Trunk of the spinal acces- 

 sory. 5. Sublingual nerve. 6. Superior 

 cervical ganglion. 7, 7. Anastomosis of 

 the first two cervical nerves. 8. Carotid 

 branch of the sympathetic. 9, 10, u, 

 12, 13. Branches of the glosso-pharyngeal. 

 14, 15. Branches of the facial. 16. Otic 

 ganglion. 17. Auricular branch of the 

 pneumogastric. 18. Anastomosing branch 

 from the spinal accessory to the pneu- 

 mogastric. IQ. Anastomosis of the first 

 pair of cervical nerves with the sublingual. 

 20. Anastomosis of the spinal accessory 

 with the second pair of cervical nerves. 21. 

 Pharyngeal plexus. 22. Superior laryn- 

 geal nerve. 23. External laryngeal nerve. 

 24. Middle cervical ganglion. (Hirsch- 

 jeld.) 



