124 DISSECTION OF THE PHARYNX. 



jugular vein and the accompanying cranial and sympathetic nerves. Behind 

 it is the spinal column, covered by muscles, viz., longus colli and rectus 

 capitis anticus major. 



In front the pharynx is united to the larynx, the hyoid bone and the 

 tongue, and to the bony framework of the nasal cavity ; but behind it is 

 unattached, and is formed chiefly of thin, fleshy strata. In the posterior 

 wall are contained elevator and constrictor muscles ; and at the upper part 

 the bag is further completed by an aponeurotic expansion which fixes it to 

 the base of the skull. The whole is lined by mucous membrane. 



The aponeurosis of attachment is seen at the upper part of the pharynx, 

 win-re the muscular fibres are absent, to connect the tube to the base of the 

 skull, and to complete the posterior boundary. Superiorly it is fixed to 

 the basilar process of the occipital, and the petrous part of the temporal 

 bone, as well as to the cartilage between the two ; but inferiorly it becomes 

 thin, and extends between the muscular and mucous strata. On this mem- 

 brane some of the fibres of the constrictor muscles terminate. 



The CONSTRICTORS are three thin muscles, which are arranged like 

 scales, the lower partly overlaying the middle, and the middle the upper. 



The inferior constrictor (fig. 28, A ), the most superficial and lowest, 

 arises from the side of the cricoid cartilage ; from the oblique line and 

 upper and lower borders of the thyroid cartilage, arid from the part of the 

 latter which is behind the oblique line. The origin is small when com- 

 pared with the insertion, for the fibres are directed backwards, radiating, 

 and are inserted into a raphe along the middle line, where it meets the 

 corresponding muscle of the opposite side. 



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

 carotid artery, and with the muscles covering the spinal column. The 

 lower border is straight, and is continuous with the fibres of the Gesopha- 

 gus ; whilst the upper border overlaps the fibres of the middle constrictor 

 (B). The recurrent nerve and vessels ( 5 ) enter beneath the lower border. 



The middle constrictor (fig. 28 B ) has nearly the same shape as the pre- 

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

 fibres arise from the great cornu of the os hyoides, from the small cornu 

 of the same bone, and from the stylo-hyoid ligament. From this origin 

 the fibres radiate, and are blended along the middle line with the other 

 muscles. 



The surfaces have connections similar to those of the preceding con- 

 strictor. The upper border is separated from the superior constrictor by 

 the stylo-pharyngeus muscle D, and ends on the aponeurosis of the pharynx, 

 about an inch from the base of the skull. The lower border descends 

 beneath the inferior constrictor ; and opposite the interval between the two 

 is the upper laryngeal nerve ( 3 ). 



The superior constrictor (fig. 28 ) is the least strong of the three 

 muscles, and wants the usual conical form. Its origin is extensive, and 

 is connected successively, from above down, with the inner surface of the 

 internal pterygoid plate (the lower third or less), with the pterygo-maxil- 

 lary ligament, with the posterior part of the mylo-hyoid ridge of the lower 

 jaw, and with the mucous membrane of the mouth and the side of the 

 tongue. The fleshy fibres ]>;i>s backwards, and are inserted on the aponeu- 

 rosis of the pharynx, as well as into the raphe along the middle line. 



The. parts in contact externally with this muscle are, the deep vessels 

 and nerves of the neck ; and internally it is lined by the aponeurosis and 

 the mucous membrane. The upper border consists of arched fibres which 



