THE DEEP MUSCLES OF THE FRONT OF THE NECK. 309 



from the third division of the fifth nerve ; the levator palati, azygos uvulae, palato-glossus and 

 palato-pharyngeus are probably supplied by the bulbar portion of the spinal accessory nerve 

 through the pharyngeal plexus. (For a summary of the evidence bearing upon the innerva- 

 tion of the palatal muscles see W. A. Turner in Journ. Anat. and Phys., xxiii, 523.) 



Actions of the muscles of the pharynx and soft palate. In considering the mode of 

 action of the constrictor muscles it is to be observed that their so-called insertion takes place 

 into a part which, owing to its connections, cannot be moved forwards, and that the constric- 

 tion of the pharynx takes place therefore mainly by movement backwards of its anterior wall, 

 the cavity being thus converted into a transverse slit. The hyoid bone and larynx are at the 

 same time carried somewhat upwards as well as backwards, in consequence of the oblique 

 direction of the larger number of the fibres of the middle and lower constrictors. The upper 

 part of the superior constrictor differs from the rest in the circumstance thab, Fcing placed 

 above the level of the palate, it cannot act directly on the food, and also that its fibres are 

 attached at both ends to parts which are immoveable. The effect of its contraction is conse- 

 quently to flatten the side-walls of this part of the pharynx, and thus to assist in approximating 

 the posterior pillars of the fauces. The stylo-pliaryngeus is the principal elevator of the pharynx 

 and larynx. The paLato-ylo^l^ besides depressing the soft palate and elevating the tongue, 

 also bring together the anterior pillars of the fauces, and thus shut off the mouth-cavity 

 from the pharynx. The palato-pliaryngei similarly depress the soft palate and raise the 

 pharynx, but their principal action is to bring together the posterior pillars of the fauces, 

 thus separating the nasal and buccal portions of the pharynx. The azyr/os uvula; raises and 

 shortens the uvula. The action of the levator palati is expressed by its name, while the tensor 

 not only tightens and supports the soft palate against pressure from below, and against the 

 traction of the depressor muscles, but is also, in the opinion of most anatomists, the agent by 

 which the Eustachian tube is opened during deglutition. It is proper, however, to remark 

 that a different view is taken by Cleland, who holds and in this he, to some extent, agrees 

 with Luschka that the tube is closed during deglutition by the thickening which 

 accompanies the contraction of the levator palati, pressing up the membranous floor of the 

 canal against the upper and outer wall, so as completely to obliterate the opening (Journ. 

 Anat., iii, 97). 



The muscles of the pharynx and soft palate are so arranged as to accomplish, in conjunc- 

 tion with those of the tongue and hyoid bone, the action of deglutition that is to say, the 

 propulsion of food into the oesophagus without any portion being permitted to pass into the 

 nasal cavity or larynx. The first stage of this operation is effected by the mylo-hyoid, stylo- 

 glossus and palato-glossus muscles, which press the tongue against the palate, and so force 

 the food backwards through the isthmus of the fauces, the hyoid bone being at the same time 

 raised by its proper elevators. The larynx is then carried upwards under the hyoid bone by 

 the thyro-hyoid and stylo-pharyngeus muscles, and the root of the tongue being drawn back- 

 wards by the stylo-glossi, the epiglottis is pressed downwards over the superior aperture of the 

 larynx, which is thus protected. Simultaneously the soft palate is raised and fixed by its 

 superior muscles, and the palato-pharyngei bring together the posterior pillars of the fauces, 

 which nearly touch one another (the uvula lying in the small interval between them) and 

 prevent the passage of the food towards the upper part of the pharynx or the posterior nares. 

 while they form an inclined surface for its guidance into the lower part of the pharynx. The 

 food being thus thrown into the grasp of the constrictors of the pharynx, these muscles 

 contract rapidly from above downwards and force it into the tube of the gullet below. 



DEEP LATERAL AND PRE VERTEBRAL MUSCLES OF THE NECK. 



The SCALENI muscles form a group of strong muscular columns, which are 

 usually three in number, but sometimes only two. All of them are subdivided 

 above into musculo-tendinous slips, corresponding in number with their vertebral 

 attachments. 



The scalenus anticus muscle is attached superiorly to the anterior tubercles 

 of the transverse processes of the third, fourth, fifth and sixth cervical vertebraa, 

 and inferiorly by a thick flattened tendon to the scalene tubercle on the upper 

 surface of the first rib. 



Relations. This muscle is deeply placed under cover of the sterno-mastoid ; on its 

 anterior surface lie the subclavian vein, omo-hyoid muscle and phrenic nerve ; behind are the 

 scalenus medius. the nerves of the brachial plexus, the subclavian artery and the pleura. On 

 its inner side the rectus anticus major arises from the same transverse processes, and the 

 ascending cervical artery lies .in the groove between the two muscles, while the internal 

 jugular vein is in front. Below the sixth cervical transverse process the vertebral vessels pass 

 backwards between the scalenus anticus and the longus colli. 



x 2 



