68 TOPOGRAPHICAL ANATOMY OF THE 



contributed to the sympathetic, hypoglossal and second cervical nerves, 

 and to the pharyngeal plexus, as well as to the sterno-hyoid, omo-hyoid, 

 sterno-thyroid and ventral straight muscles of the head. 



Dissection. — Make a longitudinal incision through the lateral wall <•£ 

 the pharynx. 



The pharynx. — The pharynx ^ is a funnel-shaped muscular and 

 membranous tube, some 15 cm. in length, extending from the clioanfe 

 and mouth, on the one hand, to the beginning of the oesophagus, on the 

 other. Functionally, it belongs to the respiratory as well as to the 

 digestive system, since through it pass both air and food. 



By means of the muscles entering into the formation of its wall, the 

 pharynx is attached to the pterygoid, palatine and hyoid bones, and the 

 thyroid and cricoid cartilages of the larynx ; while its mucous lining is 

 continuous with that of the nose, mouth, larynx and (esophagus. Its 

 relations are numerous, and among the more important the following 

 should be noted. Dorsally it is in contact with the diverticula of the 

 auditory tubes and a small part of the base of tlie cranium, while 

 ventrally it overlies the larynx. Its lateral relations include the 

 internal pterygoid muscle, the submaxillary gland, the great cornu of 

 the hyoid bone, the external carotid and external maxillary arteries, and 

 the ninth and twelfth cerebral and the cranial laryngeal nerves. 



Dissection of the wall of the tube reveals four layers, namely : 

 (1) a thin layer of pharyngeal fascia; (2) a layer of muscular tissue; 

 (3) an aponeurotic layer; and (4) a lining of mucous membrane. 

 The muscles of the pharynx have already been examined. The 

 aponeurotic layer is intimately connected with the muscles, and gives 

 attachment to some of their fibres. It is continuous with the 

 periosteum covering the bones of the base of the skull and with the 

 other connections of the pharynx, and it forms the raphe pharyngis. 



Except where it is adherent to the bones in the neighbourhood of 

 the choanse, the mucous membrane is of some thickness and contains 

 nnmerous small glands (glandulae pharyngese), the minute openings of 

 whose ducts can be detected on careful examination. Considerable 

 masses of lymphoid tissue are present in the upper part of the pharynx 

 between the openings of the auditory tubes, where they form the 

 pharyngeal tonsil (tonsilla pharyngea). This is best marked in young 

 animals. Along each lateral wall of the cavity there is a very distinct 

 fold of mucous membrane, the 'pharyngo-palatinearch (arcus pharyngo- 

 palatinus), that extends from the soft palate to above the entrance into 

 the oesophagus, where it joins the corresponding fold of the other side. 



1 (pdpvy^ (pliaryii.x) [Gr.], the throat. 



