PHARYNGEAL REGIOX. 341 



of the greater cornu of the hyoid bone, from the lesser cormi, and from the 

 stylo-hyoid ligament. The fibres diverge from their origin; the lower ones 

 descending beneath the Inferior Constrictor, the middle fibres passing trans- 

 versely, and the upper fibres ascending and overlapping the Superior Con- 

 strictor. The muscle is inserted into the posterior median fibrous raphe, blending 

 in the middle line with that of the opposite side. 



Relations. This muscle is separated from the Superior Constrictor by the 

 glosso-pharyngeal nerve and the Stylo-pharyngeus muscle ; and from the Infe- 

 rior Constrictor, by the superior laryngeal nerve. Behind, it lies on the verte- 

 bral column, the Longus Colli, and the Eectus Anticus Major. On each side it 

 is in relation with the carotid vessels, the pharyngeal plexus and some lym- 

 phatic glands. Near its origin, it is covered by the Hyo-glossus, from which 

 it is separated by the lingual artery. It lies upon the Superior Constrictor, the 

 Stylo-pharyngeus, the Palato-pharyngeus, and the mucous membrane. 



The Superior Constrictor is a quadrilateral muscle, thinner and paler than the 

 other constrictors, and situated at the upper part of the pharynx. It arises 

 from the lower third of the margin of the internal pterygoid plate and its 

 hamular process, from the contiguous portion of the palate bone and the reflected 

 tendon of the Tensor Palati muscle, from the pterygo-maxillary ligament, from 

 the alveolar process above the posterior extremity of the mylo-hyoid ridge, and 

 by a few fibres from the side of the tongue in connection with the Genio-hyo- 

 glossus. From these points, the fibres curve backwards, to be inserted into the 

 median raphe, being also prolonged by means of a fibrous aponeurosis to the 

 pharyngeal spine on the basilar process of the occipital bone. The superior 

 fibres arch beneath the Levator Palati and the Eustachian tube, the interval 

 between the upper border of the muscle and the basilar process being deficient 

 in muscular fibres, and closed by fibrous membrane. 



Relations. By its outer surface, with the vertebral column, the carotid vessels, 

 the internal jugular vein, the three divisions of the eighth nerve and the ninth 

 nerve, the Middle Constrictor which overlaps it, and the Stylo-pharyngeus. It 

 covers the Palato-pharyngeus and the tonsil, and is lined by mucous membrane. 



The Stylo-pharyngeus is a long, slender muscle, round above, broad and thin 

 below. It arises from the inner side of the base of the styloid process, passes 

 downwards along the side of the pharynx between the Superior and Middle 

 Constrictors, and spreads out beneath the mucous membrane, where some of its 

 fibres are lost in the constrictor muscle, and others joining with the Palato- 

 pharyngeus, are inserted into the posterior border of the thyroid cartilage. The 

 glosso-pharyngeal nerve runs on the outer side of this muscle, and crosses over 

 it in passing forward to the tongue. 



Relations. Externally, with the Stylo-glossus muscle, the external carotid 

 artery, the parotid gland, and the Middle Constrictor. Internally, with the 

 internal carotid, the internal jugular vein, the Superior Constrictor, Palato- 

 pharyngeus and mucous membrane. 



Nerves. The muscles of this group are supplied by branches from the pha- 

 ryngeal plexus and glosso-pharyngeal nerve ; and the Inferior Constrictor, by 

 an additional branch from the external laryngeal nerve. 



Actions. When deglutition is about to be performed, the pharynx is drawn 

 upwards and dilated in different directions, to receive the morsel propelled into 

 it from the mouth. The Stylo-pharyngei, which are much farther removed 

 from one another at their origin than at their insertion, draw the sides of the 

 pharynx upwards and outwards, its breadth in the antero-posterior direction 

 being increased by the larynx and tongue being carried forwards in their ascent. 

 As soon as the morsel is received in the pharynx, the elevator muscles relax, 

 the bag descends, and the Constrictors contract upon the morsel, and convey it 

 gradually downwards into the oesophagus. Besides its action in deglutition, 

 the pharynx also exerts an important influence in the modulation of the voice, 

 especially in the production of the higher tones. 



