A number of other muscles have been described in the soft palate of the
cat; they are, however, poorly developed and not easily distinguished.
For an account of these, see Stowell, Proceedings of the Am. Soc. of
Microscopists, 1889.
2. =The Pharynx.=--At the caudal end of the mouth cavity the passage
for the food and that for the air cross; at the cranial end the
food-passage (mouth) is ventral, the respiratory passage (nasal cavity)
dorsal. Farther caudad the food-passage (œsophagus) is dorsal, while the
respiratory passage (larynx and trachea) is ventral. In the region of
crossing there is therefore for a certain distance a common passageway
for food and air, and this is known as the =pharynx=. It extends from
the isthmus faucium, at the free caudal margin of the soft palate, to
the beginning of the œsophagus, at the dorsal or caudal margin of the
opening of the larynx. The dorsal wall of the pharynx is separated from
the base of the skull and the centra of the cervical vertebræ only by
intervening muscles (=longus capitis=, =levator scapulæ ventralis=, and
=longus colli=, Fig. 72, page 143). Its lateral and ventral walls are
supported by the hyoid bone and the cartilages of the larynx.
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.
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