THE PHARYNX 407 



laryngis occupies the greater part of the ventral wall or floor of the pharynx; it 

 is open except during deglutition. Behind this is the aditus oesophagi, the entrance 

 to the oesophagus. 



The wall of the pharynx comprises, from without inward, the muscles, the 

 pharyngeal aponeurosis, and the mucous membrane. 



The muscles of the pharynx (Mm. pharyngis) (Figs. 332, 333) are covered 

 by the pharyngeal fascia, which is attached to the base of the skull, the great cornu 

 of the hyoid bone, and the thyroid cartilage of the larynx. They are as follows: 



1. The stylo-pharyngeus arises from the medial surface of the dorsal third 

 of the great ?ornu of the hyoid bone, passes ventro-medially, and enters the wall of 

 the pharynx by passing between the pterygo-pharyngeus and palato-pharjaigeus. 

 Its fibers radiate, many bundles passing forward, others inward or backward be- 

 neath the hyo-pharyngeus. It raises and dilates the pharynx to receive the bolus 

 in swallowing. 



2. The palato-pharjmgeus arises chiefly by means of the aponeurosis of the 

 soft palate from the palatine and pterygoid bones; some fibers are attached to the 

 anterior wide part of the Eustachian tube. Its fibers pass backward on the lateral 

 wall of the pharynx, and are inserted in part into the .upper edge of the thyroid 

 cartilage, in part turn inward to end at the median fibrous raphe. Its action is to 

 shorten the pharynx, and to draw the larynx and oesophagus toward the root of the 

 tongue in swallowing.^ 



3. The pterygo-pharjmgeus is flat and triangular. It lies on the anterior part 

 of the lateral wall of the pharynx. It arises from the pterygoid bone above the 

 preceding muscle, — from which it is not distinctly separated, — crosses the levator 

 palati, and is inserted into the median raphe. . Its action is similar to the preceding. 



4. The hyo-pharyngeus may consist of two parts : 



(o) The kerato-pharyngeus is a small and inconstant muscle which arises 

 from the medial surface of the great cornu of the hyoid bone near its ventral end. 

 It passes upward and backward on the lateral face of the palato-pharyngeus, 

 turns toward the raphe, and spreads out under the next muscle. 



(b) The chondro-pharyngeus, broad and fleshy, arises from the thyroid cornu 

 of the hyoid bone and by a thin fasciculus from the lamina of the thyroid cartilage. 

 The bundles spread out and end at the median raphe. The posterior part dips 

 under the thyro-pharyngeus, while the anterior part overlies the pterygo- and 

 palato-pharyngeus. 



5. The thyro-pharyngeus arises from the lateral surface of the lamina of the 

 thyroid cartilage on and behind its oblique line. Its fibers pass forward and 

 medially to the median raphe. 



6. The crico-pharyngeus arises from the lateral part of the arch of the cricoid 

 cartilage and ends at the raphe. The fibers are directed upward, forward, and 

 inward; they blend behind with the longitudinal fibers of the oesophagus. 



The last three muscles are constrictors of the pharynx. 



The pharyngeal aponeurosis is attached to the base of the cranium. It is 

 well developed on the medial face of the palato-pharyngeus muscle and forms a 

 median raphe pharyngis dorsally, which is wide in its posterior part. 



The mucous membrane of the pharynx is continuous with that of the several 

 cavities which open into it. It is thin and closely adherent to the base of the skull 

 in the vicinity of the posterior nares, where the muscular wall is absent. Behind 

 the Eustachian openings there is a median cul-de-sac, the pharyngeal recess (Re- 

 cessus pharyngeus) . The recess is somewhat variable, but is usually about an inch 

 in depth and will admit the end of the finger. In the ass and mule it is much deeper. 

 Here also the muscular wall is absent and the mucous membrane lies against the 



1 Vermeulen states that the pharyngeal orifice of the Eustachian tube is opened by the 

 contraction of that part of the muscle which is attached to the tube. 



