Frog's Oral Cavity
...nd the intrinsic muscle fibers, which run vertically, transversely, and longitudinally, allow it great range of movement. The upper surface is covered with small projections called papillae, which give it a rough texture. The color of the tongue, usually pinkish-red but discolored by various diseases, is an indication of health. The tongue serves as an organ of taste, with taste buds scattered over its surface and concentrated toward the back of the tongue. In chewing, the tongue holds the food against the teeth; in swallowing, it moves the food back into the pharynx, and then into the esophagus when the pressure of the tongue closes the opening of the trachea, or windpipe. It also acts, together with the lips, teeth, and hard palate, to form word sounds. 3. Esophagus, portion of the digestive tube that conducts food from the mouth to the stomach. When food is swallowed it passes from the pharynx into the esophagus, initiating rhythmic contractions (peristalsis) of the esophageal wall, which propel the food along toward the stomach. The walls of the esophagus are lined with mucous glands that continue the lubrication of the food as it is conducted to the stomach. The human esophagus is about 10 in. (25 cm) long and 1 in. (2.5 cm) in diameter. 4. Glottis, opening to the larynx and lungs. Air enters and leaves by way of the glottis. 5. Internal Nares, two small openings inside the frogs mouth, that the frog is able to breathe through its nostrils. 6. External Nares, two small openings outside the frogs, on top of the upper lip, that the frog is able to breathe through its nostrils. 7. Eustachian tube, a hollow structure of bone and cartilage extending from the middle ear to the rear of the throat, or pharynx, technically known as the pharyngotympanic or auditory tube. By permitting air to leave or enter the middle ear, the tube equalizes air pressure on either side of the eardrum. The tube can become blocked, as by enlarged adenoids or the mucous secretions of a cold, so that external and internal pressure become imbalanced. Earache and diminution of hearing may result. The tube may also serve as a pathway to the ear for infections of the throat. A common ear disease known as Otitis Media, usually appearing in early childhood, is thought to be related to the Eustachian tube. The tube tends to be shorter and more horizontal among children, factors which facilitate the spread of infections from upper respiratory diseases to the middle ear, as well as the accumulation of fluids in the region. 8. Tympanum, The outer ear is the visible portion; it includes the skin-covered flap of cartilage known as the auricle, or pinna, and the opening (auditory canal) leading to the eardrum (tympanic membrane). The middle ear, separated from the outer ear by the eardrum, contains three small bones, or ossicles. Because of their shapes, these bones are known as the hammer (malleus), anvil (incus), and stirrup (stapes). Air reaches the middle ear through the Eustachian tube , or auditory tube, which connects it to the throat. 9. Vocal Sacs, most frogs, especially males, are quite vocal. As the frog forces air through the voice box, or larynx, the vocal cords vibrate to make calls distinctive of its species. A much louder sound is produced by the males of species that possess vocal sacs, which swell enormously when the frog calls to attract a mate. The frog’s tongue is attached at the front of the mouth instead of at the rear, and it is covered with a sticky substance, making it an efficient trap. 10. Maxillary teeth, to hold on the food and to grip it tightly 11. Maxilla, The facial bones include the two nasal bones, which constitute the upper portion of the bridge of the nose; the two lacrimal bones, which are located in each eye orbit next to the nose, close to the tear ducts; the maxillary bone, which constitutes the upper jaw; the mandible, which constitutes the lower jaw; the two palatine bones of the hard palate; the vomer, which, with a part of the ethmoid bone, constitutes the nasal septum; and the two inferior turbinates of the nose. 12. Vomerine Teeth, to prevent the escape of any prey before swallowing. 13. Eye, The human eye is a spheroid structure that rests in a bony cavity (socket, or orbit) on the frontal surface of the skull. The thick wall of the eyeball contains three covering layers: the sclera, the choroid, and the retina. The sclera is the outermost layer of eye tissue; part of it is visible as the “white” of the eye. In the center of the visible sclera and pro...