The image at left shows the dorsal surface of the tongue, and the
most common of the lingual papillae, the filiform
type. These are slender projections of cornified epithelium,
sometimes "swallow tailed" in shape. They're distributed all
over the surface of the tongue, and raked backwards. The
"spines" on a cat's tongue are a nice example of this type of
papilla, and they're what gives the tongue its rough feel and velvety
appearance. They have no sensory function.
In large animals, such as cows, the filiform papillae can be very
large, up to perhaps 5.0 mm long. When they get this big, they
sometimes have a "core" of CT inside. But in smaller animals
they are pretty much entirely epithelial in nature.
