THE CONSTRICTOR MUSCLES. 657 



The INFERIOR CONSTRICTOR (fig. 232, A), the most superficial, Lower 

 irises from the side of the cricoid cartilage, and from the inferior arises from 

 x>rnu. oblique line, and upper border of the thyroid cartilage. The laiynx 

 >rigin is small when compared with the insertion, for the fibres the middle" 

 radiate as they pass backwards, to be inserted along the middle line, line: 

 where the muscles of opposite sides join. 



The outer surface of the muscle is in contact with the sheath of parts in 

 he carotid vessels, and with the muscles covering the spinal column. SStMt* 

 The lower border is nearly horizontal, and beneath it the inferior 

 aryngeal nerve and vessels ( 5 ) pass ; while the upper border ascends 

 very obliquely and overlaps the middle constrictor. A few of the 

 owest iibres of the muscle turn downwards, and are continued into 

 ;he longitudinal fibres of the oesophagus. 



The MIDDLE CONSTRICTOR (fig. 232, B) has a similar shape to the pre- Middle 

 ceding, that is to say, it is narrowed in front and expanded behind. constnctor 

 Its fibres arise from the great and small cornua of the hyoid bone on JJ?| f J . 

 i deeper plane than the hyo-glossus and from the stylo-hyoid liga- 

 nent. From this origin the fibres radiate, and are blended along the 

 niddle line with those of the opposite muscle. 



The posterior surface of this muscle is to a great extent concealed relations, 

 jy the inferior constrictor. Laterally, it touches the carotid sheath ; 

 ind its origin is beneath the hyo-glossus muscle, the lingual artery 

 passing between the two. Its upper border is separated from the 

 superior constrictor by the stylo-pharyngeus ; and in the interval 

 Between the origins of the middle and inferior constrictors are the 

 superior laryngeal nerve and vessels. 



The SUPERIOR CONSTRICTOR is thinner than the others, and of a Upper 

 quadrilateral form. It has a broad origin from the following parts 

 n succession, commencing above, the lower end of the internal pterygoid 

 pterygoid plate and the hamular process, the pterygo-maxillary jaw and 

 igament, the hinder part of the mylo-hyoid ridge of the lower jaw, to 

 the mucous membrane of the mouth, and the side of the tongue. 

 The fibres pass backwards, and are inserted by joining those of the inserted 

 fellow muscle along the middle line, where a tendinous raphe is 

 formed between the two for the upper half of their depth. Some of 

 the highest fibres reach the tubercle on the under surface of the 

 oasi-occipital and others end on the aponeurosis of the pharynx. 



The parts in contact with this muscle externally are the deep relations: 

 vessels and nerves of the neck at the side, the middle constrictor 

 and prevertebral muscles behind : internally are the aponeurosis of 

 the pharynx and the palato-pharyngeus muscle. The upper border interval 

 forms an arch with the concavity upwards extending from the ptery- mwfe'iuQd 

 goid plate to the basilar process ; and the space between it and the skun - 

 base of the skull is occupied by the aponeurosis of the pharynx, which 

 projects outwards above the muscle, and by the levator palati, Eusta- 

 chian tube and inferior palatine artery. The attachment to the 

 pterygo-maxillary ligament corresponds with the origin of the bucci- 

 nator muscle (i) between the two maxillary bones. 



Action of constrictors. The muscles of both sides contracting at the use of 



constrictors 

 D.A. U U 



