MUSCLES OF PHARYNX AND PALATE 1137 



the lowest fibres are continuous with the muscular fibres of the oesophagus, and the upper over- 

 lap the middle constrictor (fig. 894). The ?ierve-siipply of all three constrictors is from the 

 pharyngeal nerve. 



Near the upper border the superior laryngeal nerve and artery pierce the thyreo-hyoid 

 membrane to reach the larynx. The inferior laryngeal nerve ascends beneath the lower border 

 immediately behind the crico-thyreoid articulation. 



The middle constrictor is a fan-shaped muscle which arises from the lesser cornu of the 

 hyoid bone and from the stylo-hyoid hgament (chondro-pharyngeus), and from the whole 

 length of the greater cornu (cerato-pharyngeus). The diverging fibres are inserted into the 

 median raphe, and blend with those of the opposite side. The lower fibres of the muscle descend, 

 beneath the inferior constrictor, to the lower part of the pharynx; the upper overlap the superior 

 constrictor, and reach the basilar process of the occipital bone, whilst the middle fibres rxin 

 transversely (fig. 894). 



The glosso-pharyngeal nerve passes downward above its upper border, the stylo-pharyngeus 

 passes between it and the superior constrictor, and near its origin it is overlapped by the hyo- 

 glossus and crossed by the lingual artery. 



The superior constrictor is quadrilateral in shape, pale, and thin (fig. 894). It arises 

 from the lower third of the hinder edge of the median lamina of the pterygoid process and its 

 hamular process (pterygo-pharyngeus), from the pterygo-mandibular ligament (bucco-pharyn- 

 geus), from the posterior fifth of the mylo-hyoid ridge of the mandible (mylo-pharyngeus), 

 and from the side of the root of the tongue (glosso-pharyngeus). The fibres pass backward to 

 be inserted into the median raphe, the highest reaching the pharyngeal tubercle. The Eu- 

 stachian tube and the levator veli palatini are placed above the superior arched border, and the 

 space (sinus of Morgagni) between this and the basilar process, devoid of muscular fibres, is 

 strengthened by the pharyngeal aponeurosis, this portion of it being semilunar in shape. 



The stylo-pharyngeus arises from the base of the styloid process internally. It passes down- 

 ward and medialward to reach the pharynx between the superior and middle constrictors. 

 Its fibres spread out as it descends beneath the mucous membrane. At the lower border of 

 the superior constrictor some of its fibres join fibres of the pharyngo-palatinus (palato-pharyn- 

 geus), and are inserted into the posterior border of the thyreoid cartilage (fig. 894); the rest 

 blend with the constrictors. The nerve-supply of the stylo-pharyngeus is from the glosso-phar- 

 yngeal nerve. 



The levator veli palatini — named from its action on the velum of the soft palate — is some- 

 what rounded in its upper, but flattened in its lower, half. Origin. — (1) The inferior surface 

 of the petrous portion of the temporal, anterior to the orifice of the carotid canal; (2) the lower 

 margin of the cartilage of the auditory (Eustachian) tube. Insertion. — The aponeurosis of 

 the soft palate; the terminal fibres of the muscles of each side meet in the middle line in front 

 of the m. uvulae. Structure. — Its origin is by a short tendon; the muscle then becomes fleshy, 

 and continues so to its insertion. Nerve-supply. — From a pharyngeal branch (plexus) of the 

 vagus. Action. — (1) To raise up the velum of the soft palate, and bring it in contact with the 

 posterior wall of the pharynx; (2) to narrow the pharyngeal opening and to widen the isthmus of 

 the auditory (Eustachian) tube. (According to Cleland, it closes the pharj'ngeal opening of this 

 tube.) 



The tensor veli palatini— named from its action on the velum of the soft palate — is a thin, 

 flat, and narrow sheet. Origin. — (1) The scaphoid fossa of the sphenoid; (2) the angular spine 

 of the sphenoid; (3) the lateral side of the membranous and cartilaginous wall of the auditory 

 (Eustachian) tube. Insertion. — (1) Into the transverse ridge on the under surface of the hori- 

 zontal plate of the palate bone; (2) the aponeurosis of the soft palate. 



Structure. — Its belly as it descends between the pterygoideus internus and the internal 

 pterygoid plate is m.uscular. On approaching the hamular process it becomes tendinous, and 

 continues so to its insertion. A bursa is interposed between the hamular process and the tendon. 

 The belly of the muscle is at nearly a right angle with its tendon. Nerve-supply. — From the 

 mandibular division of the trigeminus through the tensor palati branch of the otic ganglion. 

 Actions. — (1) Tightens the soft palate; (2) opens the auditory (Eustachian) tube during deglu- 

 tition. 



The m. uvulae. — so named by reason of its position in the uvula. Origin. — (1) From the 

 aponeurosis of the soft palate and tendinous expansions of the two tensores veli palatini. In- 

 sertion. — Into the uvula. Structure. — The muscle consists of two narrow parallel strips lying 

 on each side of the middle fine of the palate. Nerve-supply. — From the pharyngeal branch of 

 the vagus. Action. — To draw up the uvula. 



Origin of the muscles. — According to W. H. Lewis, the tensor palati is a derivative of the 

 mandibular arch (probably split off from the pterygoid mass); the levator palati and m. uvulae 

 come with the facial musculature from the hyoid arch; the glosso-palatine, stylo-pharyngeus 

 and pharyngeal constrictors probably from the third visceral arch, in a pre-muscle mass visible 

 in a 9 mm. embryo. The adult innervation of the pharjmgeal muscles does not agree entirely 

 with this, however. The pharyngeal muscles (as above stated) are innervated chiefly from the 

 vagus, whereas if derived from the third arch their innervation from the glosso-pharyngeus 

 would be expected. 



Process of swallowing. — In the act of swallowing, practically aU of the muscles of the mouth, 

 tongue, palate and pharynx are involved. By compression of the lips and cheeks, together 

 with elevation of the tongue, the food is forced backward through the faucial isthmus into the 

 oral pharjTix. Constriction of the faucial isthmus by the glosso-palatine muscles assists in 

 preventing a return to the mouth. By the action of the levator palati, tensor palati, and 

 pharjmgo-palatine muscles, the soft palate is retracted and tightened, with constriction of the 

 pharyngeal isthmus, so as to prevent the passage of the food upward into the nasal pharynx. 

 The pharynx is drawn upward by the stylo-pharyngeus, and the pressure produced by the 

 pharjTigeal constrictors (the contraction beginning above and extending downward) forces 

 the food downward through the laryngeal pharynx and into the oesophagus. Passage of the 

 food into the larynx is prevented by constriction of the superior aperture of the larynx. 

 72 



