226 



CHORDATE ANATOMY 



adenoid tissue pitted with numerous crypts which tend to be a source of 

 infection. The hypertrophy of adenoid tissue, especially that of the soft 

 palate in childhood, interferes with breathing and often requires surgical 

 treatment. The soft palate is a muscular partition separating digestive 

 and respiratory portions of the pharynx. From its posterior border 

 hangs the uvula. (Fig. 213) 



Seven cavities open into the pharynx — the mouth, the two nasal 

 passages, the two Eustachian tubes, the larynx, and the esophagus. 



PARIETAL BONP 

 GYRUS CINGULI 

 PITUITARY, 

 SUBDURAL CAVITY- 

 FRONTAL LOBE- 

 FRONTAL BONE- 



RIGHT CEREBRAL HEMISPHERE 



ORPUS CALUDSUM 



NASAL BONE 

 SPHENOID BONE- 

 NASAL CONCHAE 

 EUSTACHIAN TUBE 

 MAXILLA 

 MOUTH CAVITY- 

 PALATINE BONE- 

 VESTIBULE- 

 SOFT PALATE 

 M. GENIOGLOSSUS 

 MANDIBLE- 

 M. GENIOHYOID 



M. MYLOHYOID 



FORNIX 



PINEAL GLAND 



DURA MATER 

 -OCCIPITAL BONE 

 EREBELLUM 



PHARYNX- 

 EPIGLOTTIS- 



LARYNX>==^ 



SPINAL CORD 

 SPLENIUS 

 TRAPEZIUS 



SEMISPINALIS 

 CERVICIS 



ESOPHAGUS' 



Fig. 213. — A median longitudinal section of the human head sho-wing the relations 

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

 Braus.) 



Three divisions may be distinguished, oral, nasal, and laryngeal. The 

 palatine tonsils lie in the oral portion, the nasal passages and Eustachian 

 tubes open into the nasal portion, while the larynx opens into the laryngeal 

 portion. When food enters the pharynx the entire pharynx is raised by 

 the contraction of the stylo-pharyngeal muscles while the constrictor 

 muscles of the pharynx squeeze the bolus towards the esophagus. The 

 nerve supply of the pharynx comes chiefly from the glossopharyngeal. 

 Since the pharyngeal region is closely associated with the respiratory 

 organs of vertebrates, the description of the evolution and development 

 of the pharynx is omitted here and will be found in the following chapter. 



