464 THE MUSCULAR SYSTEM. 



(2) Movements of the Thyreoid Cartilage. The thyreoid cartilage is raised and lowered 

 during speech and deglutition. 



(3) Movements of the Tongue. The chief movements of the tongue in speech and de- 

 glutition are elevation and depression, protrusion and retraction, and lateral movements. 



(4) Movements of the Head. The sterno-mastoid muscles, acting together, flex the head on 

 the vertebral column, assisted by the supra-hyoid and infra-hyoid muscles. The sterno-mastoid 

 muscle of one side, acting alone, bends the head to the same side, and simultaneously rotates it 

 to the opposite side, as seen in torticollis (wryneck). 



(5) Movements of the Shoulder Girdle. The omo-hyoid and sterno-mastoid muscles have 

 already been included among the elevators of the shoulder girdle. 



(6) Respiration. The muscles in the front of the neck are auxiliary muscles in extraordinary 

 or difficult inspiration. The masseter and temporal muscles fix the mandible ; the hyoid bone 

 is raised and fixed by the supra-hyoid muscles ; and the sternum is raised by the sterno-mastoid 

 and infra-hyoid muscles. 



The Muscles of the Pharynx. 



The muscular envelope of the pharynx is composed of two strata. The externa 

 or circular layer consists of the three fan-shaped constrictor muscles ; the inter na 

 or longitudinal layer consists of the fibres of the Stylopharyngeus and pharyngo 

 palatinus muscles. 



M. Constrictor Pharyngis Superior. The superior constrictor muscle 

 arises successively from the inferior half of the posterior border of the media 

 lamina of the pterygoid process (pterygopharyngeus), from the pterygo 

 mandibular raphe (buccopharyngeus), from the mylo-hyoid line of the mandible 

 (mylopharyngeus) (Fig. 410, p. 461), and from the mucous membrane of the 

 floor of the mouth (glossopharyngeus). 



The muscular fibres radiate backwards, and are inserted, for the most part, intc 

 a raphe extending down the posterior wall of the pharynx in the median plane 

 The highest fibres are attached to the pharyngeal tubercle of the occipital bon< 

 (Fig. 396, p. 444), and the lowest fibres are overlapped by the middle constrictor 

 A crescentic interval occurs above the muscle, below the base of the skull, in whicl 

 the auditory tube and the levator and tensor veli palatini muscles appear. It 

 lower border is separated from the middle constrictor by the stylopharyngeu 

 muscle. 



M. Constrictor Pharyngis Medius. The middle constrictor muscle arise 

 from the stylo -hyoid ligament and from both cornua of the hyoid bone (chondrc 

 pharyngeus, ceratopharyngeus). 



From its origin the muscular fibres radiate backwards, to be inserted into th 

 median raphe on the posterior aspect of the pharynx. 



