316 THE PHARYNX. 



The muscles (Fig. 92) cover the back -and sides of the 

 pharynx in one uniform membranous sheet or layer, and 

 are called constrictors. They are three in number, the 

 inferior, middle, and superior constrictors of the pharynx. 

 These are symmetrical muscles, lying upon either side, and 

 connected with the tendinous line or raphe, which runs 

 along the centre of the back part of the pharynx. 



Constrictor pliaryngis inferior, arises from the inferior 

 cornu, and posterior ala of the thyroid cartilage, and from 

 the side of the cricoid. Its fibres radiate, (some ascending, 

 and others transverse,) to be inserted into the raphe on the 

 back of the pharynx, along with its fellow. The superior 

 fibres overlap the middle constrictor. The superior la- 

 ryngeal nerve passes along the upper, and the inferior 

 laryngeal beneath the lower border of this muscle. 



Constrictor pliaryngis medius partly covered by the last, 

 and of a triangular shape, arises from the appendix and 

 cornu of the os-hyoides, and from the posterior thyro-hyoid 

 and styloid ligaments. Its fibres ascend, run transversely, 

 and descend. It is inserted into the mesial line, and by 

 its ascending fibres, into the cuneiform process of the 

 occipital bone. 



Constrictor pharyngis superior is above the last, and 

 separated from it by the stylo-pJiaryngeus muscle, and 

 glosso-pharyngeal nerve. It surrounds the upper and pos- 

 terior part of the pharynx, and arises from the internal 

 pterygoid plate, from the upper jaw, behind the last molar 

 tooth ; from the pterygo maxillary ligament ; from the side 

 of the base of the tongue, and from the posterior portion 

 of the mylo-hyoid ridge. From this extensive origin, the 

 fibres proceed backwards and upwards, and are inserted 

 into the middle line, and cuneiform process of the occipi- 

 tal bone. - r*' 



Function. The constrictor muscles are the prime agents 

 in deglutition, and conduct the food, by their successive 

 contractions, from the pharynx into the oesophagus. 



Stylo-pliaryngeus is a slender muscle arising from the 

 root of the styloid process. It passes to the side of the 



