Craniad the pharynx continues, usually, without break into the cavity lying dorsad of the soft palate. But at the time of swallowing the free edge of the soft palate is pushed dorsad against the dorsal wall of the pharynx, while the caudal part of the pharynx is drawn craniad, so as to form a cavity continuous with that of the mouth. In this way the cavity above the soft palate is completely separated at the time of swallowing from the rest of the pharynx. This separated portion is known as the =nasopharynx=: it is strictly a portion of the respiratory passage, as the food does not pass into it. The nasopharynx is continuous craniad by the =choanæ= with the nasal cavity; it forms a horizontal tube between and ventrad of the perpendicular plates of the palatine bones, and has the same craniocaudal extent as the soft palate. Its dorsal wall lies against the basis cranii and the longus capitis muscles; its lateral walls against the pterygoid muscles and the perpendicular plates of the palatine bones; its ventral wall is the soft palate. At the middle of its length, at the junction of its dorsal and lateral wall, are two longitudinal slits about three millimeters long. These are the medial openings of the =Eustachian tubes=, by which the nasopharynx communicates with the tympanic cavity.
The =pharynx proper=, situated caudad of the nasopharynx, is smaller than the latter. It is bounded craniad by the epiglottis and the margin of the soft palate, and is continuous between the two, by the isthmus faucium, with the mouth cavity. Its floor is formed by the cranial end of the larynx. At its caudal end it passes dorsally into the œsophagus, while ventrally it communicates with the larynx. Its walls are muscular.
MUSCLES OF THE PHARYNX (Fig. 96).--=M. glossopharyngeus= (_i_).
_Origin._--Some fibres on the ventral and lateral part of the genioglossus (_f_) leave that muscle near its caudal end. They form a thin band of diverging fibres which pass outside of the cranial horn of the hyoid. A similar sheet of fibres leaves the midventral part of the styloglossus (_e_). The two sheets unite and the united muscle crosses the hyoid, turns dorsad, and has its
_Insertion_ into the median dorsal raphe of the pharynx.