Section III—Mouth, Oral Cavity, and Pharynx
Open the mouth by cutting through the angle of the jaw on each side, so that you can reveal the oral cavity and pharynx, as shown in Figure 6.9. Note the large tongue on the floor of the oral cavity.
The tongue is attached anteriorly and folded back into the oral cavity, so that its distal, bifid end lies posteriorly. The tongue is extended to catch insects by rotating it dorsally around its anterior attachment. A single row of small teeth, often easier to feel than to see, lies around the margin of the upper jaw. As described above, these teeth are mostly maxillary teeth. The few premaxillary teeth are near the midline. The teeth lie on the lateral side of the maxillary groove, which extends around the margin of the upper jaw. The pterygoid ridge is medial to the groove. A row of vomerine teeth is present on each of the vomers. These teeth lie farther posteriorly near the midline of the roof of the oral cavity.
FIGURE 6.9 Anterior view of the oral cavity and pharynx of the frog.
A series of openings enter the oral cavity. The internal choanae are prominent and lie posterior to the vomerine teeth. The large posterolateral openings are the auditory tubes, which lead to the middle ear cavities. The floor of the orbits lies between the internal nares and auditory tubes. Pressure on this area will force the eyeballs up into their open position. Ventrally in the oral cavity, posterior to the tongue, is the slit-like glottis, which leads to the lungs (see below). It is on a small projection, the laryngeal prominence, which is formed by cartilages. Laterally on the floor of the oral cavity, on each side of the anterior end of the glottis, is a small opening in males that lead to a vocal sac. The sacs are used in calling during the mating season, but are difficult to find. The entrance into the esophagus is posterior to the glottis. Probe it gently to verify that it does indeed extend posteriorly.
Break the tympanic membrane to expose the middle ear cavity (Figure 6.8b). The columella (see above), which has a cartilaginous distal portion, passes through this cavity to the membrane. Probe the cavity to verify that it connects with the oral cavity through the auditory tube.
Key Terms: Mouth, Oral Cavity, and Pharynx
columella esophagus auditory tube
(Eustachian tube) glottis internal choanae laryngeal prominence lungs
maxillary groove maxillary teeth oral cavity pharynx premaxillary teeth pterygoid ridge tongue vomerine teeth