. Cunningham's Text-book of anatomy. Anatomy. 1142 THE DIGESTIVE SYSTEM. neighbouring cavities (Eig. 901). These are the two choanae ( posterior nares) on the anterior wall of the pars nasalis, and the two tubae auditivae ( Eusta- chian tubes) on its lateral walls; the isthmus of the fauces leading into the mouth from the oral part; the orifice of the larynx on the anterior wall of the laryngeal part of the cavity ; and finally, the opening of the oesophagus at its inferior end. Pars Nasalis( Naso-Pharynx) (Figs. 901and902).—Although morphologic- ally and developmentally this is a
. Cunningham's Text-book of anatomy. Anatomy. 1142 THE DIGESTIVE SYSTEM. neighbouring cavities (Eig. 901). These are the two choanae ( posterior nares) on the anterior wall of the pars nasalis, and the two tubae auditivae ( Eusta- chian tubes) on its lateral walls; the isthmus of the fauces leading into the mouth from the oral part; the orifice of the larynx on the anterior wall of the laryngeal part of the cavity ; and finally, the opening of the oesophagus at its inferior end. Pars Nasalis( Naso-Pharynx) (Figs. 901and902).—Although morphologic- ally and developmentally this is a portion of the true pharynx, it is functionally an annexe to the respiratory portion of the nasal cavities, and both anatomically and Posterior end of middle concha Pharyngeal tonsil Maxillary sinus Posterior end of inferior concha Glands in hard palate Third molar. Orbit Posterior edge of nasal septum Torus tubarius Pharyngeal orifice of auditory tube Glosso-palatine arch Palatine tonsil Buccinator (cut) Pharyngo-palatine arch. Pharyngo-nasal isthmus Tongue Fig. 902.—The Nasal Part of the Pharynx from the Front. frontal section was made through the upper part of the head ; this passed immediately in front of the posterior edge of the nasal septum, and extended into the mouth below. Through the choanse, the nasal part of the pharynx is seen. The prominence of the posterior margin of the ostium pharyn- geum of the auditory tube, and the lymph nodules constituting the pharyngeal tonsil, should be noted. The palatine arches and tonsils, and an unusually wide pharyngo-nasal isthmus, are also seen. functionally it is distinctly marked off from the digestive tube. It differs from the rest of the pharynx in that its cavity remains, under all conditions, a distinct open chamber incapable of obliteration, owing to the fact that all its walls, with the single exception of the floor, are practically immovable. The cavity of the pars nasalis is irregular in shape, and is enclosed by si
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