Page 929 - Fundamentals of anatomy physiology

916 Unit 5 Environmental Exchange
geniohyoid and mylohyoid muscles. p. 375 The palatine
processes of the maxillary bones and the horizontal plates
of the palatine bones form the hard palate. A prominent cen-
tral ridge, or raphe (RA. -fee), extends along the midline of the
hard palate. The mucosa lateral and anterior to the raphe is
thick, with complex ridges. When your tongue compresses food
against the hard palate, these ridges provide traction. The soft
palate lies posterior to the hard palate. A thinner and more deli-
cate mucosa covers the posterior margin of the hard palate and
extends onto the soft palate.
The posterior margin of the soft palate supports the uvula
(U. -vu. -luh), a dangling process that helps prevent food from
entering the pharynx too soon (Figure 24–6a). On either
side of the uvula are two pairs of muscular pharyngeal arches
(Figure 24–6b). The more anterior palatoglossal (pal-a-to. -
GLOS-al) arch extends between the soft palate and the base
of the tongue. A curving line that connects the palatoglossal
arches and uvula forms the boundaries of the fauces (FAW-se. z),
the arched opening between the soft palate and the base of the
tongue. The fauces serve as the passageway between the oral
cavity and the oropharynx. The more posterior palatopharyn-
geal (pal-a-to. -fa-RIN-je. -al) arch extends from the soft palate to Three pairs of salivary glands secrete into the oral cavity
the pharyngeal wall. A palatine tonsil lies between the palato-
glossal and palatopharyngeal arches on either side.
The Tongue
24 The tongue (Figure 24–6) manipulates food inside the mouth
and occasionally brings in foods (such as ice cream on a
cone). The primary functions of the tongue are (1) mechani-
cal processing by compression, abrasion, and distortion;
(2) manipulation to assist in chewing and to prepare food for
swallowing; (3) sensory analysis by touch, temperature, and
taste receptors; and (4) secretion of mucins and the enzyme
lingual lipase.
We can divide the tongue into an anterior body, or oral
portion, and a posterior root, or pharyngeal portion. The superior
surface, or dorsum, of the body contains a forest of fine projec-
tions, the lingual papillae. p. 594 The thickened epithelium
covering each papilla assists the tongue in moving materials. A
V-shaped line of vallate papillae roughly marks the boundary
between the body and the root of the tongue, which is located
in the oropharynx (Figure 24–6a).
The epithelium covering the inferior surface of the tongue
is thinner and more delicate than that of the dorsum. Along the
inferior midline is the lingual frenulum (FREN-u. -lum; frenum,
bridle), a thin fold of mucous membrane that connects the
body of the tongue to the mucosa covering the floor of the oral
cavity (Figure 24–6a). Ducts from two pairs of salivary glands
open on either side of the lingual frenulum, which serves to
prevent extreme movements of the tongue. However, an overly
restrictive lingual frenulum hinders normal eating or speech.
Properly diagnosed, this condition, called ankyloglossia (ang-ki-
lo. -GLOS-e. -uh), can be corrected surgically.
The tongue’s epithelium is flushed by the secretions of
small glands that extend into the underlying lamina propria.
These secretions contain water, mucins, and the enzyme ­lingual
lipase. This enzyme works over a broad pH range (3.0–6.0),
enabling it to start lipid digestion immediately. Because lin-
gual lipase tolerates an acid environment, it can continue to
break down lipids—specifically, triglycerides—for a consider-
able time after the food reaches the stomach.
The tongue contains two groups of skeletal muscles. The
large extrinsic tongue muscles perform all gross movements
of the tongue. p. 374 The smaller intrinsic tongue muscles
change the shape of the tongue and assist the extrinsic muscles
during precise movements, as in speech. Both intrinsic and ex-
trinsic tongue muscles are under the control of the hypoglossal
cranial nerves (N XII).
Salivary Glands
(Figure 24–7a). Each pair has a distinctive cellular organization
and produces saliva, a mixture of glandular secretions, with
slightly different properties:
1. The large parotid (pa-ROT-id) salivary glands lie infe-
rior to the zygomatic arch deep to the skin covering the
lateral and posterior surface of the mandible. Each gland
has an irregular shape. It extends from the mastoid process
of the temporal bone across the outer surface of the mas-
seter muscle. The parotid salivary glands produce a serous
secretion containing large amounts of salivary amylase. This
enzyme breaks down starches (complex carbohydrates). The
Clinical Note
Mumps The mumps virus most often targets the salivary
glands, especially the parotid salivary glands, but other
o­ rgans can also be infected. Infection typically occurs at
5–9 years of age. The first exposure stimulates the produc-
tion of antibodies and, in most cases, confers permanent
immunity. In postadolescent males, the mumps virus can
also infect the testes and cause sterility. Infection of the
pancreas by the mumps virus can produce temporary or
permanent diabetes. Other organ systems, including
the central nervous system, are affected in severe cases.
A mumps vaccine effectively confers active immunity.
Widespread administration of that vaccine has almost
eliminated mumps in the United States.