Page 393 - Anatomy and Physiology of Farm Animals, 8th Edition

378 / Anatomy and Physiology of Farm Animals

(A) (B)
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Figure 20-8. (A) Fungiform papillae from rabbit tongue (4×). Notice the presence of taste buds on the
lateral sides of papillae (circle). (B) Close up of taste buds (40×). Arrowhead indicates pore at apex of taste
bud through which dissolved substances can reach the taste cells of the bud. Source: photomicrographs
courtesy of Gretchen Delcambre, Colorado State University, Colorado, USA.

which is thickly covered with prominent Care must be exercised not to enter this
conical papillae. Similar cornified projec­ diverticulum while passing a stomach tube
tions cover the inside of the lips and cheeks. or giving medications via a balling gun.

Tonsils
Pharynx
Tonsils are more or less circumscribed
The pharynx (pl. pharynges) is the com­ aggregations of lymphatic nodules found
mon passage for food and air, is caudal to in association with the mucous membranes
oral and nasal cavities, and is lined by of the mouth and pharyngeal region
mucous membrane and surrounded by (Fig. 20‐10). The histologic organization of
muscles. The pharynx can be divided into tonsils is described in Chapter 16.
nasal (nasopharynx), oral (oropharynx), In humans, each of two obvious pala-
and laryngeal (laryngopharynx) portions, tine tonsils lies in a pocket on the lateral
so named for their association with these wall of the pharynx ventral to the soft pal­
regions (see Fig. 19‐2). ate and adjacent to the base of the tongue
The muscles of the walls of the pharynx (these are readily seen with a mirror as
are responsible for the orderly directing of elongate nodules on each side of your
air, food, and liquids in such a way that air throat, unless, of course, they have been
from the nasal cavity is directed into the lar­ removed). In the horse, ox, and sheep,
ynx and food and liquids are directed into the these palatine tonsils are in about the same
esophagus. Thus, the paths of air and swal­ relative position, within the submucosa,
lowed substances must cross in the pharynx; and completely covered by mucous mem­
pharyngeal dysfunction can have severe brane. In other words, the tonsils do not
consequences for the airway, which must be project into the pharynx at all in these ani­
protected from foodstuffs (Fig. 20‐9). mals. The ruminant palatine tonsil features
The pharyngeal recess in the horse is a a deep cleft, the tonsillar crypt, which
median niche at the caudodorsal angle of increases the surface area through which
the nasopharynx (Fig. 20‐10). The pig has a the lymphatic tissue may come in contact
pharyngeal diverticulum that opens into with antigens (Figs. 19‐2 and 20‐7). In the
the dorsal wall of the pharynx near the pig the palatine tonsils lie within the sub­
beginning of the esophagus. stance of the soft palate.