326 THE MUSCULATURE 



elevate and dilate the pharynx and elevate the larynx. The muscles of the pharynx are de- 

 scribed on page 1134. 



The orifices of the various passages into the pharynx are dilated or constricted by muscular 

 action. The orifices of the nasal passages, the Eustachian tubes, and the mouth are controlled 

 mainly by the musculature of the soft palate and pharynx. The orifice of the larynx is con- 

 trolled by special muscles which act in conjunction with those of the suprahyoid group, the 

 tongue, and the pharynx. 



The soft palate is a muscular partition which is continued backward from the hard palate 

 between the buccal cavity and the naso-pharyngeal orifice and then bends downward between 

 the back part of the mouth and the nasal part of the pharynx, terminating in a median pro- 

 jection, the uvula. Above, on each side, back of the fold of tissue {plica salpingo-palatinus) 

 which descends from the ventral border of the orifice of the Eustachian tube and which marks 

 laterally the passage from the nose into the pharynx, there is a muscle, the levator veli palatini 

 (fig. 343'). This arises from the petrous portion of the temporal bone and from the Eustachian 

 tube descends to the middle of the side of the soft palate and then spreads out broadly on its 

 dorsal side. The muscle from each side interdigitates to some extent with that of the other 

 side. These muscles raise the soft palate toward the upper part of the posterior wall of the naso- 

 pharynx and thus shut off the nose from the buccal portion of the pharynx during deglutition. 

 The sides of this portion of the pharynx are, meanwhile, constricted by the superior constrictors 

 of the pharynx and by the pharyno-palatinus muscles described below. Contraction of the 

 levator veli palatini tends to cause folds of tissue to close firmly the opening of the Eustachian 

 tube. This is counteracted by the tensor veli palatini muscles (fig. 343). One of these arises 

 on each side from the pterygoid region of the sphenoid bone, and is inserted into the anterior 

 part of the soft palate by a tendon which passes beneath the hamular process of the pterygoid 

 process. Contraction of this pair of muscles flattens the anterior part of the soft palate and 

 exerts a traction which dilates the orifice of the Eustachian tube. Most authorities state that 

 the Eustachian tube is thus opened each time we swallow. As air is admitted into the middle 

 ear the tensor tympani muscle contracts so as to prevent too sudden an effect on the ear drum 

 (Jonnesco.) 



Dorsal to the fibres of the elevator of the palate in the soft palate next the median line on 

 each side there extends from the hard palate into the uvula a small muscle, the muscle of the 

 uvula, which lifts the tip of this and shortens the soft palate from front to back thus enlarging 

 the opening from the mouth into the pharynx. On each side of the uvula the posterior edge of 

 the soft palate is continued backward and downward into a fold, the arcus pharyngo-palatinus, 

 which contains a muscle, the pharyngo-palatimis (fig. 865). This arises from the soft palate, 

 passes downward and backward on the inner side of the lateral wall of the pharynx and divides 

 into two fasciculi, one of which is attached to the larynx, the other to the median raphe. The 

 muscle constricts the pharynx at the junction between the nasal and buccal portions and elevates 

 the larynx. As the bolus of food is passed from the dorsum of the tongue into the pharynx 

 the bucco-pharyngeal opening is dilated by the contraction of the elevators of the palate and 

 uvular muscles and the opening into the naso-pharynx is closed not only by the soft palate 

 being raised against the posterior wall of the naso-pharynx but also by the lateral folds raised 

 on each side by the pharyngo-palatinus against t he uvula. Meanwhile the larynx is raised by 

 the pharyngo-palatinus and the stylo-pharyngeus, as well as by the suprahyoid muscles, and 

 carried forward by the hyo-mandibular subdivision of the latter muscles so that the opening 

 from the pharynx into the oesophagus is dilated for the passage of food. At the same time the 

 opening into the larynx is constricted from above, the larynx being carried forward beneath the 

 tongue so that the epiglottis slants somewhat backward. This backward slant is aided by the 

 constriction of the thyreo-hyoid muscle which raises the thyreoid cartilage toward the hyoid 

 bone and by the stylo-glossus muscle which pulls the tongue backward over the larynx. The 

 opening into the larynx is constricted at the sides and behind by the contraction of muscles 

 which run in the aryepiglottic folds and by the thyreo-arytenoid and transverse arytenoid 

 muscles. At the end of deglutition the larynx is pulled back from beneath the base of the 

 tongue by the middle and inferior constrictors of the pharynx and the opening is again dUated. 

 The buccal cavity may be shut off from the pharynx by the action of the muscles which pass 

 in. the glosso-palatal folds from the soft palate to the mouth in front of the tonsils. These 

 glosso-palntal muscles elevate the folds in which they lie, depress the soft palate, and, if the 

 dorsum of the tongue be raised, shut off the buccal cavity. The muscles of the soft palate are 

 described on p. 1134. 



The uvular muscle, the levator veli palaini, the glosso-palatinus and the pharyngo- 

 palatinus muscles are supplied by the pliaryngeal plexus. The tensor veli palatini is sup- 

 plied by the mandibular division of the fifth nerve. The pharyngeal muscles are supplied 

 by the glosso-pharyngeal, the vagus, and the spinal accessory cranial nerves. 



The larynx lies in the neck, but since the intrinsic muscles of the larynx from the standpoint 

 of embryology and comparative anatomy belong with the musculature of the head, it is con- 

 venient to refer to them i)riefly hero rather than to treat of them with the intrinsic muscles of the 

 neck. A full description of The laryngeal muscles is given in the section on the larynx (fig. 981) . 

 They develop from tissue wliich corresponds with that which in fishes gives rise to the muscles 

 of the gills and arc innervated l)y the nerves which in the fishes innervate the gills, the tenth 

 pair fvagus) of cranial nerves. The movements of the laryngeal cartilages are such as to 

 approximate or draw apart the vo(;al cords and to loosen or make them tense. The approxi- 

 mation of the vocal cords is produced by the rotation medialward of the vocal processes of the 

 arytenoid cartilages brought about by the lateral crico-arytcnoid and transverse arytenoid 

 muscles. The drawing apart of the vocal cords is produced l)y the posterior crico-arytenoids. 

 The vocal cords are made long, thin and tense by the crico-thyreoid. They are shortened and 

 thickened by the Ihyreo-ar ijtenoid (externus) and the vocalis. The inferior laryngeal branch of 



