Inside the Mouth

[BrokenWing]

BrokenWing Chronicles
Inside the Mouth

Inside of the mouth, the oropharynx, contains the tongue, glottis, choana, palate, salivary glands, esophagus, opening of the avian equivalent of the Eustachian tubes (the  pharyngotympanic tubes) and larygeal mound. The tongue has a bone in it. The tongue is adapted for collecting food, manipulating food and swallowing. For example, the tongue of the birds in the lory and lorikeet families is the most specialized of the parrots. The lory tongue is called a '"brush-tongue," which refers to a cluster of elongated papillae that are normally only visible when the bird is feeding on liquid or soft foods, or when preening another bird.

At the base of the tongue, the glottis and the laryngeal mound are located. The larynx of mammals is used for vocalization, but it is the syrinx, located down much further, that is responsible for sound production in birds. The glottis is the opening to the windpipe, or trachea. The choana is located on the roof of the mouth. It is a slit that connects through some passages to the nostrils. One really neat difference that birds have is that the glottis will fit snugly into the choanal slit when the bird closes its mouth, and the bird will then have a closed connection from the nostrils to the windpipe. When a human breathes through the nostrils, the air goes through the back of the throat, which is an open area, to the trachea through the larynx. There are little projections, called papillae, that normally are found at the edges of the choanal slit. Other papillae, pointing towards the back of the throat, may be found in the oropharynx. A second, smaller slit is located behind the choanal slit. This is the opening to the middle ears, the infundibular cleft, of birds, connected by a tube, called the pharyngotympanic tube. Birds with middle ear infections often have a red, swollen cleft. This cleft is important for birds that fly at great altitudes, as it helps equalize pressure in the middle ear. I'll bet you never thought that birds ears might pop when they ascend during flight, like ours do when we humans fly!

In the past, it was thought that birds had a poorly developed sense of taste. Taste buds lie at the base of the tongue, in most species of birds. Some birds have taste buds on the inside of the tip of the lower and upper bills and there are several sites on the roof of the oropharynx, near the choana. In parrots, the taste buds are on the roof of the oropharynx on either side of the choana, and on the floor of the oropharynx at the front end of the laryngeal mound. Mallard ducks have less than 500 taste buds, compared to the 10,000 of a human and 17,000 in the rabbit. Birds do have a sense of taste, and do show definite taste preferences, as we all know!

Examination of the oropharynx is extremely important when a bird is evaluated by an avian vet. I use a strong, focal light source and magnification to closely evaluate the choana, papillae and infundibular cleft. It gives the experienced avian vet a tremendous amount of information regarding the overall health of the bird. If the choana is swollen, if the papillae are blunted or absent, if the infundibular cleft is reddened, if abscesses are present, or if thick, white ropy mucus is present, it gives the vet a good idea if malnutrition, vitamin A deficiency, bacterial or yeast infection or middle ear infections may be present, to name just a few. Internal papillomatous disease (papillomas) can occur throughout the gastrointestinal tract, and lesions may be present in the oropharynx. They may look like small, pink wart-like lesions. If your vet does not closely examine this area during a check-up, ask her why. It should be examined in every bird!

The oropharynx is variably colored in different species of birds. It may be pink, black or mottled. It takes experience to determine if the throat is blotchy pigmented, or if disease is present. For example, the oropharynx of the blue and gold macaw may be uniformly black, or it may contain pink areas. Pink areas could indicate internal papillomatous disease, or they could be normal. I always recommend that breeders get into the habit of examining the oropharynx of all of their baby birds daily, to look for changes that could be a problem. It is easy to begin learning the normals from the abnormals, if a breeder looks at the throats every day.


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