Functional Anatomy of the Goat - Goat Science and Production - page 109

ease the understanding of the functional anatomy of the
digestive system, it may be divided in two major groups
of structures: the prediaphragmatic and the postdiaphrag-
matic digestive systems. FunctioFnally, the former is
adapted to prehension, mastication, insalivation, and deglu-
tition of the alimentary bolus, whereas the latter is respon-
sible for the digestion of food and elimination of wastes.

called the oral vestibulum. The space surrounded by the
teeth is called the oral cavity proper, where the tongue lies.
As annex glands of the prediaphragmatic digestive system,
the salivary glands will be described later. They are located
around the oral cavity, but their product, the saliva, is
emptied into the oral cavity.

T HE T ONGUE
The tongue is a very mobile organ; however, it is not used
in prehension of food. A root, a body, and an apex can be
distinguished with ease. On the surface of the body, an ele-
vation called torus linguae is characteristic for all rumi-
nants. The tongue is capable of a wide variety of movements,
and it is covered by a mucosa provided with papillae.
The lingual papillae are fi liform (with a cornifi ed tip),
fungiform (mushroom-shaped), and vallate (mushroom-
like papillae embedded into the lingual mucosa and sur-
rounded by a circular groove). The fi liform papillae have
a mechanical role, whereas the other two types bear taste
buds and are involved functionally as the primary stage in
the perceiving of taste (through the gustatory system; see
the Gustatory Organ in the Sense Organs). The fi liform
papillae may be lens-shaped (lenticular papillae) or coni-
cal-shaped (conical papillae). The fi liform papillae are
scattered on the surface of the tongue, the fungiform papil-
lae are numerous along the borders of the apex, and the
vallate papillae, in numbers of 12-18, form two irregular
rows on the torus linguae.
The muscles moving the tongue originate from the
hyoid apparatus. The narrow symmetrical space between
the tongue and the mandible is called the lateral sublingual
recess. The tongue is supplied by the hypoglossal nerve (to
the muscles), by the trigeminal, facial, glossopharyngeal,
and vagus nerves (for the taste buds) and the mucosa for
tactile, pain, and temperature stimuli.

The Prediaphragmatic Digestive System

T HE O RAL C AVITY
The oral cavity, or the mouth, is located in the head, under
the nasal cavity. It starts with the superior (upper) and
inferior (lower) lips and continues caudally with the oro-
pharynx. The roof of the oral cavity is represented by the
hard palate covered by a mucosa. The fl oor is rostrally
bony and caudally muscular. The lateral walls (the cheeks)
are muscular (Figure 6.22).
Goat lips are very mobile. The upper lip lacks the phil-
trum (present in the sheep), which favors the grasping and
tearing of browse (Smith and Sherman, 1994). The lips and
the incisive teeth are responsible for the prehension of
food.
The hard palate is covered by a mucosa with transversal
palatine ridges, having the mechanical role of holding the
alimentary bolus within the oral cavity (notice that while
grazing, the head is oriented toward the ground). At the
level of the fi rst ridge, the incisive papilla can be identifi ed.
In front of the latter, the mucosa of the hard palate is very
thick and called the dental pad. This structure replaces the
upper incisive teeth. The hard palate continues caudally
with the soft palate. The bony fl oor of the oral cavity is the
incisive part of the body of the mandible, whereas muscles
support the tongue. The lateral walls of the oral cavity are
muscular, including the masseter muscle, involved in
mastication.
The mucosa of the oral cavity is provided with papillae
of different colors, sizes, and shapes, which play a similar
mechanical role as the palatine ridges, holding the alimen-
tary bolus within the oral cavity. One symmetrical eleva-
tion of the mucosa in the upper oral vestibulum is the
parotid papilla, where the parotid duct opens. On the fl oor
of the oral cavity proper, a symmetrical sublingual car-
uncle can be seen, like a mucosal fl ap protecting the open-
ings of the mandibular and major sublingual salivary ducts.
The mucosa of the oral cavity is supplied by the trigeminal
nerve.
The tongue and the teeth are the major structures inside
the oral cavity. When the mouth is closed, the space
between the teeth and the lips and the lateral walls is

T EETH
There are three categories of teeth: incisors, premolars, and
molars. The premolars and molars are collectively called
“cheek teeth.” All teeth are implanted into dental alveoli—
bony sockets in some bones of the skull. There are only
four inferior incisors on each side in all ruminants. From
the midline to the periphery, they are called central,
fi rst intermediate, second intermediate, and corner inci-
sors. The latter are considered canine teeth that have
migrated rostrally. The superior incisors are replaced by
the mucosal dental pad. Three superior and inferior pre-
molars and three molars are on each side. There are decidu-
ous teeth, which appear immediately after birth. Some of
them are replaced by permanent teeth. Therefore, there are