Page 203 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

Digestive system (apparatus digestorius) 185

They appear as small, mushroom-shaped elevations that
· gustatory papillae (papillae gustatoriae):
VetBooks.ir − fungiform papillae (papillae fungiformes), protrude slightly above the tongue surface. Fungiform
papillae are not as strongly keratinised as mechanical
− vallate papillae (papillae vallatae) and
papillae. It is thought that fungiform papillae may contain
− foliate papillae (papillae foliatae).
thermoreceptors. Occasional taste buds are present in
the epithelium in calves and horses; in carnivores they are
MECHANICAL PAPILLAE abundant. Taste buds are more numerous in young ani-
Mechanical papillae typically have a connective tissue core mals during the suckling period.
housing numerous nerve fibres and mechanoreceptors. Vallate papillae occur at the transition from the body
Tactile stimuli are received by free nerve endings in the to the root of the tongue. Horses and pigs have one pair
epithelium. The papillae are supplied by a dense vascular of vallate papillae; two to three pairs are present in car-
network. nivores. Vallate papillae are most numerous in ruminants
The filiform papillae of horses, pigs and goats mani- (up to 24 on each side in sheep) (Figures 10.8 and 10.9).
fest as soft threads of epithelium that give the surface of Each papilla is surrounded by an annular sulcus, the outer
the tongue a velvet-like smoothness. In cattle, sheep and boundary of which is slightly elevated. The papilla itself
cats, small keratinised spines project towards the pharynx does not protrude beyond the surface of the tongue. The
from a connective tissue core. These are responsible for sulcus is lined by epithelium. On the papillary side, the
the characteristic roughness of the surface of the tongue epithelium contains numerous taste buds (number varies
in these species. In cats, the protruding spines are sup- with species).
ported on their rostral aspect by an additional papilla Tubulo-acinar serous glands (Ebner’s glands, gusta-
(Figure 10.7). tory glands) lie deep to the vallate papillae, between the
Blunt conical papillae are found in carnivores, pigs, cat- tela submucosa and muscle fibre bundles. Their secretory
tle and small ruminants. In neonatal carnivores and piglets, product passes through a branched system of ducts into
the margins of the tongue bear elongated marginal papil- the base of the sulcus. Continuous production of secretion
lae. These form part of the lateral boundary of the oral ensures that dissolved nutrients within the saliva are con-
fissure and facilitate sucking. stantly washed from the surface of the taste buds, allowing
new gustatory sensations to be detected.
GUSTATORY PAPILLAE Foliate papillae are located laterally near the root of
In gustatory papillae, the stratified squamous epithelium the tongue. They are well developed in the horse, less so
contains specialised structures, termed taste buds, that in pigs and carnivores and absent in ruminants. These
are concerned with the perception of taste stimuli (see gustatory papillae consist of folds of mucous membrane
Chapter 16, ‘Receptors and sense organs’). separated by transverse furrows (Figure 10.9). The walls
Fungiform papillae are distributed over the dorsum, of the furrows house numerous taste buds. Dense accu-
margins and parts of the ventral surface of the tongue. mulations of gustatory glands, similar in structure and

10.7 Filiform papilla (cat). This mechanical papilla is characterised by an aborally directed, conical spine aris-
ing from a primary papilla. An additional, supportive papilla lies on the oral aspect of the primary papilla.
Haematoxylin and eosin stain (x32).

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