The Digestive System
Te superior tongue surface bears papillae, peglike projec-
tions of the underlying mucosa
. Te conical
roughen the tongue surface, helping us lick
semisolid foods (such as ice cream) and providing friction for
manipulating foods. Tese papillae, the smallest and most nu-
merous type, align in parallel rows on the tongue dorsum. Tey
contain keratin, which stiﬀens them and gives the tongue its
whitish appearance. Te mushroom-shaped
are scattered widely over the tongue surface. Each has a vas-
cular core that gives it a reddish hue. ±en to twelve large
are located in a V-shaped row at the back of the tongue.
Tey resemble the fungiform papillae but have an additional
surrounding furrow. Pleatlike
are located on the
lateral aspects of the posterior tongue.
Te fungiform, vallate, and foliate papillae house taste buds,
but those on the foliate papillae function in taste primarily in
infancy and early childhood. Serous cells just beneath the foliate
and vallate papillae secrete
a fat-digesting enzyme
that operates in the acid environment of the stomach.
Immediately posterior to the vallate papillae is the
, a groove that distinguishes the portion of the tongue
that lies in the oral cavity (its body) from its posterior portion in
the oropharynx (its root). Te mucosa covering the root of the
tongue lacks papillae, but it is still bumpy because of the nodular
, which lies just deep to its mucosa (Figure 23.8).
Check Your Understanding
How does the oral vestibule differ from the oral cavity proper?
Which structure forms the roof of the mouth?
Besides preparing food for swallowing, the tongue has
another role. What is it?
For answers, see Appendix H.
internally by the gums and teeth is the
Te area that lies within the teeth and gums is the
u-lum) is a median fold that
joins the internal aspect of each lip to the gum (Figure 23.7b).
, forming the roof of the mouth, has two distinct
parts: the hard palate anteriorly and the so² palate posteriorly
(Figure 23.7). Te
is underlain by the palatine bones
and the palatine processes of the maxillae, and it forms a rigid
surface against which the tongue forces food during chewing.
Te mucosa on either side of its
fe), a midline ridge, is
slightly corrugated, which helps create friction.
is a mobile fold formed mostly of skeletal muscle
that rises reﬂexively to close oﬀ the nasopharynx when we swallow.
±o demonstrate this action, try to breathe and swallow at the
Laterally, the so² palate is anchored to the tongue by the
and to the wall of the oropharynx by the more
. Tese two paired folds
form the boundaries of the
arched area of the oropharynx that contains the palatine tonsils.
Projecting downward from the free edge of the so² palate is the
occupies the ﬂoor of the mouth (Figure 23.7). Te
tongue is composed of interlacing bundles of skeletal muscle
ﬁbers, and during chewing, it grips the food and constantly
repositions it between the teeth. Te tongue also mixes food
with saliva forming it into a compact mass called a
lus; “a lump”), and then initiates swallowing by pushing the bo-
lus posteriorly into the pharynx. Te versatile tongue also helps
us form consonants (k, d, t, and so on) when we speak.
Te tongue has both intrinsic and extrinsic skeletal muscle
are conﬁned in the tongue and are
not attached to bone. Teir muscle ﬁbers, which run in several
diﬀerent planes, allow the tongue to change its shape (but not
its position), becoming thicker, thinner, longer, or shorter as
needed for speech and swallowing.
extend to the tongue from their points
of origin on bones of the skull or the so² palate, as described in
Chapter 10 (see ±able 10.2 and Figure 10.8). Te extrinsic muscles
alter the tongue’s position. Tey protrude it, retract it, and move
it from side to side. Te tongue has a median septum of connec-
tive tissue, and each half contains identical muscle groups. A fold
of mucosa called the
secures the tongue to the
ﬂoor of the mouth and limits its posterior movements.
Children born with an extremely short lingual frenulum are o²en
referred to as “tongue-tied” because restricted tongue movement
distorts speech. Tis congenital condition, called
(“fused tongue”), is corrected surgically by snipping the frenulum.
Dorsum of tongue
of the tongue
Dorsal surface of the tongue, and the tonsils.