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PHYSIOLOGY 



The efferent fibres of the ninth and tenth nerves are derived partly 

 from the dorsal nucleus of the vagus and accessory nerves lying 

 externally to the nucleus of the twelfth nerve, and partly from the 

 nucleus ambiguus, a mass of grey matter lying deeper in the medulla 

 (Fig. 206). 



The ninth or glossopharyngeal nerve supplies motor fibres to the 

 muscles of the pharynx and the base of the tongue, and secretory 

 fibres to the parotid gland. The sensory fibres convey impulses from 

 the tongue, the mouth, and pharynx, the fibres originating outside 

 the central nervous system in the ganglion-cells of the ganglion 

 petrosum and the ganglion superius. It also contains inhibitory 

 fibres to the respiratory centre. 



FIG. 206. Plan of the origin of the tenth and twelfth nerves. 



pyr, pyramid ; nXII, nucleus of hypoglossal ; XII, hypoglossal nerve ; 

 dnX, XI, dorsal nucleus of vagus and accessory ; n.amb, nucleus ambiguus ; 

 fs, fasciculus solitarius (descending root of vagus and glossopharyngeal) ; 

 fsn, its nucleus ; X, crossing motor fibre of vagus ; g, cell in ganglion of 

 vagus giving origin to a sensory fibre ; (IV, descending root of fifth ; cr, 

 corpus restiforme. 



The tenth nerve, vagus or pneumogastric, is joined by the accessory 

 part of the spinal accessory, so that the two nerves may be con- 

 sidered together. It has both afferent and efferent functions. 

 Efferent functions : 



Motor to levator palati and three constrictors of pharynx. 



Motor to muscles of larynx. 



Inhibitory to heart. 



Motor to muscular walls of oesophagus, stomach, and small 



intestine. 



Motor to unstriated muscle in walls of bronchi and bronchioles. 

 Secretory to glands of stomach and possibly to pancreas. 



