3o6 



COMPARATIVE ANATOMY 



The Pharynx 



The pharynx is that part of the ahmentary canal where the respiratory 

 and digestive passages cross one another. The constricted opening 

 through which the mouth cavity communicates with the pharynx is the 

 isthmus faucium. It is bordered by the soft palate above, the tongue 

 below, and the glossopalatine arch on each side. The glossopalatine arch 

 partially covers the palatine tonsil, a mass of adenoid tissue pitted with 



PARIETAL BONF 

 GYRUS CINGULI 

 PITUITARY, 



RIGHT CEREBRAL HEMISPHERE 



RPUS CALLDSUM 

 FORNIX 



PINEAL GLAND 



SUBDURAL CAVITY- 

 FRONTAL LOBE- 

 FRONTAL BONE 



DURA MATER 



NASAL ^^^^—^^m^S^^^iai^ffi Iwaai^B^Si. ' J \y/'^w'~°^'^^^"'^^ ^°^^ 



SPHENOID BONE- ' j • ^ 



NASAL C0NCHAE-="=*^^^^^^^^^^^^^^3^"^^^^--^ ^"^^^^^^Sa^^^S^^^^^EREBELUW 



EUSTACHIAN TUBE 

 MAXILLA- 

 MOUTH CAVITY- 

 PALATINE BONE- 

 VESTIBULE- 

 SOFT PALATE 

 M. GENIOCLOSSUS 

 MANDIBLE- 

 M. GENIOHYOID--^'^^^^ 



M. MYLOHYOID 



PHARYNX^ 



EPIGLOTTIS'' 



LARYNX ^\?U, ^ - 



ESOPHAGUS' XENTRA 



Fig. 257. — A median longitudinal section of the human head showing the rela- 

 tions between digestive and respiratory passages in the pharyngeal region. (Redrawn 

 after Braus.) 



numerous crypts which tend to be a source of infection. The isthmus is 

 surrounded on all sides by adenoid tissue, the lingual tonsil being included 

 in the ring. The hypertrophy of adenoid tissue, especially that of the 

 soft palate in childhood, interferes with breathing and often requires 

 surgical treatment. (Fig. 257) 



The soft palate is a muscular partition separating digestive and 

 respiratory portions of the pharynx. From its posterior border hangs 

 the uvula. By the action of the palatine muscles, the food pushed by 

 the tongue into the pharynx is forced backwards towards the esophagus 

 and prevented from entering the nasal portion of the pharynx. 



