The photograph, left, was so good in terms of showing the hard (not that hard, more firm) almost invisible hair like structures on the tongue that we can feel when licked by our cat, that I had to post an article about it.
We know that the cat's tongue is multipurpose. It is used to groom the cat, grab food and hold liquid (and lick us).
The "hairs" are called papillae. As can be clearly seen in the photograph, they point backwards like barbs almost. They contain the same material that makes our fingernails and the claws of the cat (keratin) , which provides the necessary hardness to the papillae that makes them so useful.
The highly effective hair-like structures not only help to grab and strip the food from the surface it is on, they also helps to push the food to the back of the mouth and down the throat. When the cat has hunted and grabbed prey the papillae helps to secure the prey in place. It is impressive to see my cat grab prawns from a flat plate solely with her tongue (no hands Dad, look....)
Grooming is essential for a cat. Without the tongue this simply would not be possible. You can read a bit about the less well known and obvious reasons for grooming by clicking on this link. The spiny surface of the cats tongue acts like a comb. As they groom saliva wets the fur, which is licked dry. Dirt and loose hair is removed. A kitten is taught by the mother how to do this. And grooming is often mutual between siblings and for example dogs and cats sometimes.
A fine photo and detailed close up - by Malingering (Flickr)
A cat's sense of taste is acute (as is the cat's hearing and sense of smell - it must feel as if you are bombarded with stimuli if you are a cat). The sense of smell apparently comes from taste buds on papillae at the tip and sides of the tongue. These taste buds are also located at several locations on the roof and back of the mouth. Cats have a limited ability to taste sweet flavours. It is said, in fact, that cats cannot taste sweet food. This is probably a simply adaptation to the fact that the cat is an obligate carnivore; flesh, high in protein and fats contains almost no simple sugars (src: The Cat by Linda P Case).
Cat are probably more concerned with the smell of food which often dictates whether it is eaten or not. The sensation of flavour is a combination of taste and smell. When there is little left on the plate my cat will smell the plate for particles of food that remains; her eyesight being almost redundant at this stage.
A cat's tongue is also sensitive to the texture of the food (called mouthfeel). And as is the case for humans, the tongue is sensitive to temperature as well.
Finally it is astonishing to see how effective a cat can lap up liquid with her or his tongue. Recent research, at the Massachusetts Institute of Technology, Virginia Tech and Princeton University in the USA, has explained how this is achieved. "Sophisticated hydrodynamics" are employed - yes, it's very scientific and shows how anatomically sophisticated the humble domestic cat is.
The cat by the way is far superior at licking up liquid to the dog! The dog slurps and splashes. The cat expertly uses the forces of gravity and inertia in a carefully balanced manner.
The study shows that, when drinking, the curled tongue (it is not always curled - see video below) is the only part of the tongue to touch the liquid. It is the only part of the cat to touch the liquid, in fact. The tongue brushes the surface and as it does this a "column of fluid forms between the moving tongue and the liquid's surface. The cat then closes its mouth, pinching off the top of the column to drink"1.
Gravity, of course, pulls the liquid off the tongue while inertia keeps it on the tongue as inertia creates a tendency for the liquid to carry on moving in the direction it has been pulled. It is a question of timing for the cat. If the cat delays in closing the mouth and drinking, gravity will pull the liquid off the tongue. In other words, gravity overtakes inertia if there is a delay. The video below is a slo-mo version of a cat's tongue in action.
A domestic cat laps up liquid about 4 times per second, each time bringing up 0.1 milliliters of liquid. The big cats lap up liquid at a slower rate apparently but the balance between inertia and gravity is maintained.
The cat's sophisticated innate intelligence allows it to judge how fast to move the tongue to maximise liquid uptake.
All cats whether they are wild or domesticated employ the same technique.
Photograph at top of page: copyright Gossamer1013
From Cats Tongue to Cat Anatomy
1. Daily Mail Nov 12th 2010.