TME HEAD AND NECK 1265 



Insertion. — ^The median raphe on the posterior vrall of the 

 pharynx, where it meets its fellow of the opposite side. 



The muscle is fan-shaped, and its fibres consequently diverge 

 very much as they pass round to reach the raphe. The inferior 

 fibres descend very obhquely, and are overlapped by the upper 

 fibres of the inferior constrictor, the internal laryngeal nerve and 

 superior lar5mgeal artery- passing to the thyro-hyoid membrane 

 between the two muscles anteriorly. The middle fibres pass more 

 or less transversely. The superior fibres ascend obhquely, and reach 

 the basilar process of the occipital bone. They overlap the loWer 

 portion of the superior constrictor, and the stylo-pharyngeus muscle 

 and glosso-pharyngeal nerve pass between the two. The lingual 

 artery rests upon the muscle at the great comu of the hyoid bone. 



Superior Constrictor — Origin. — (i) The lower third of the posterior 

 border of the internal pterygoid plate, and the hamular process of 

 the sphenoid bone; (2) the posterior aspect of the pterygo-mandi- 

 bular ligament, along which it meets the buccinator muscle ; (3) the 

 posterior extremity of the mylo-hyoid ridge of the lower jaw; (4) the 

 mucous membrane of the mouth; and {5) the side of the tongue. 



Insertion. — The median raphe on the posterior wall of the pharynx, 

 where it meets its fellow of the opposite side. A feW of the highest 

 fibres are inserted into the pharyngeal tubercle on the under surface 

 of the bcisilar process of the occipital bone. 



The muscle is somewhat four-sided. The fibres for the most part 

 pass horizontally, but the lower fibres radiate in a downward 

 direction, whilst the upper fibres curve backwards and upwards. 

 The lower portion of the muscle is overlapped by the upper part 

 of the middle constrictor, the stylo-phan^ngeus muscle and glosso- 

 pharyngeal nerve passing between the two. Between the upper, 

 concave border and the base of the skull there is an interval 

 occupied by the pharyngeal aponeurosis, which is here stronger than 

 elsewhere, and so compensates for the absence of muscular fibres. 

 This interval is semilimar, and is known as the sinus of Morgagni. 



Nerve-supply of the Constrictor Muscles. — The nerves are derived 

 from the pharyngeal plexus, which is formed by the pharyngeal 

 branch of the pnevmiogastric, the pharyngeal branches of the 

 glosso-pharyngeal, and sympathetic filaments. The motor fibres 

 of the plexus are derived from the pharyngeal branch of the 

 pneumogastric, but their ultimate source is the bulbar portion of 

 the spinal accessory nerve. The inferior constrictor muscle also 

 receives twigs from (i) the external larjTigeal branch of the superior 

 larj-ngeal nerve, and (2) the inferior or recurrent larjoigeal nerve 

 as it passes beneath the lower border of the muscle. 



Action. — The constrictor muscles are concerned in the act of 

 deglutition. The superior constrictor and upper portion of the 

 middle constrictor act upon the naso-pharynx, that is, the compart- 

 ment of the pharynx which hes above the soft palate, and is in 

 communication with the nasal fossje through the posterior nares. 

 They narrow the naso-pharjTix in the lateral direction, and this 



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