LATERAL AND PK^EVEETEBEAL MUSCLES OF THE NECK. 467 



It descends, between the internal pterygoid muscle and the medial pterygoid 

 lamina, and ends in a tendon which hooks round the pterygoid hamulus. The 

 tendon is inserted, beneath - the levator veli palatini, into the posterior border of 

 the hard palate, and into the aponeurosis of the soft palate. 



M. Glossopalatinus. The glossopalatinus (O.T. palatoglossus), occupying 

 the inferior surface of the soft palate and the glosso-palatine arch, has already been 

 described with the muscles of the tongue (p. 463). 



Nerve-Supply. The muscles of the soft palate (except the tensor veli palatini, which is 

 innervated through the otic ganglion by the trigeminal nerve) are supplied through the pharyn- 

 geal plexus by the accessory nerve. 



Actions of the Muscles of the Pharynx and Soft Palate. The muscles of the pharynx 

 and soft palate are chiefly brought into action in the act of swallowing. This act is divided into 

 a voluntary stage, in which the bolus lies anterior to the arches of the fauces, and an involuntary 

 stage, during which the food passes from the mouth through the pharynx. The movements 

 occurring during the passage of food through the mouth are'as follows : the cheeks are compressed 

 by the action of the buccinator muscles; the tongue, hyoid bone, and thyreoid cartilage are 

 successively raised upwards by the action of the muscles which close the mouth and elevate the 

 hyoid bone. By these means the food is pushed backwards between the palatine arches. 



At the same time, by the contraction of the glosso-palatinus and pharyngo-palatinus, the 

 palatine arches of the fauces are narrowed, while the muscles of the soft palate, contracting, 

 tighten the soft palate, and by bringing it in contact with the posterior wall of the pharynx, 

 shut off the nasal portion of the cavity. The elevation of the tongue, hyoid bone, and larynx 

 simultaneously causes the elevation of the epiglottis and the superior aperture of the larynx, 

 which is closed by the approximation of the aryteenoid cartilages and the combined action of 

 laryngeal muscles (aryteenoideus, thyreoarytsenoideus, and thyreoepiglotticus). The food thus 

 slips over the anterior surface of the epiglottis and the closed superior aperture of the larynx, 

 and between the palatine arches on either side, into the pharynx. It is now clasped by 

 the constrictor muscles, which, by their contractions, force it down into the 03sophagus. The 

 contraction of the constrictor muscles results in a flattening of the pharynx and elevation of its 

 anterior attachments. 



During the act of swallowing, it is generally thought that the auditory tube is opened by 

 the contraction of the tensor veli palatini muscle, which arises from it. It has been held, on 

 the other hand, that the auditory tube is closed during swallowing by the compression of ita 

 wall by the contraction of the levator veli palatini. 



Deep Lateral and Prsevertebral Muscles of the Neck. 



Three series of muscles are comprised in this group : (1) vert ebro- costal (scaleni, 

 anterior, medius, and posterior), (2) vertebro- cranial (longus capitis and rectus 

 capitis anterior, and lateralis), and (3) vertebral (longus colli). They clothe the 

 anterior surface of the cervical portion of the vertebral column for the most part, 

 and are in relation anteriorly with the pharynx and oesophagus, and the large 

 vessels and nerves of the neck. 



M. Scalenus Anterior. The scalenus anterior (O.T. anticus) arises from the 

 anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth 

 cervical vertebrae. 



. It descends, posterior -to the carotid sheath and subclavian vein, to be inserted 

 into the scalene tubercle and ridge on the first rib (Fig. 414, p. 468). 



It is separated posteriorly from the scalenus medius by the roots of the brachial 

 plexus, the subclavian artery, and the pleura, and it is concealed by the sterno- 

 mastoid muscle. 



M. Scalenus Medius. The scalenus medius arises from the posterior tubercles 

 of the transverse processes of the cervical vertebras, from the second to the sixth 

 inclusive. 



It descends in the posterior triangle, behind the subclavian artery and the 

 roots of the brachial plexus, to be inserted into the rough impression on the first 

 rib behind the subclavian groove (Fig. 414, p. 468). The muscle is pierced by the 

 dorsal scapular and long thoracic nerves. 



It is separated from the scalenus anterior by the subclavian artery and the 

 roots of the brachial plexus. 



M. Scalenus Posterior. The scalenus posterior arises, behind the scalenus 

 medius, from the posterior tubercles of the fourth, fifth, and sixth cervical transverse 

 processes. It is inserted into an impression on the outer side of the second rib. 





