Q: Why is a cat’s tongue like sandpaper?

A: If you look at a cat’s tongue with a magnifying glass (and good luck trying to do that, by the way!), you’ll see it’s covered with row after row of barbs. For you scientific types, these little structures that line the surface of a cat’s tongue are called filiform papillae. They’re hooked (like the wirery half of Velcro), and are directed toward the throat.

These barbs help to hold prey while eating, and they also help a cat keep her fur in perfect (or should we say purrfect?) condition, pulling out dead and dying hairs along with any debris picked up in the day’s travels. Cats can actually feel when a few hairs are out of place, so that tongue is also a convenient, built-in hairbrush.

It’s the start of an assembly line for some mighty fine hairballs, as well. Since the hooks direct items down the throat — like an auger — it’s difficult for cats to expel fur objects (or yarn, fishing line or other things that rightly ought to be expelled) from their mouths. This is one reason cats swallow rather than spit out fur, and then hack it up as hairballs.

Other papillae of the tongue are involved with taste detection. The filiform papillae can’t taste food, but they do hold food in contact with the tongue long to enable the cat to taste it.

Cats can function with no teeth, but they must have at least half their tongue to survive.

Q: Is a dog’s mouth really cleaner than a human’s?

A: We’re sorry, but … yuk! You don’t have to be an oral hygiene expert to know that any animal who eats cat poop, horse doo and garbage, who licks his own genitalia and is fascinated by the rear ends of other dogs isn’t exactly going to have a clean mouth. It’s hard to imagine how such an idea ever got started, especially when you consider that we humans routinely floss and brush our teeth, gargle, visit the dentist and worry about the germs that cause bad breath.

So is a dog’s mouth cleaner a human’s? Not at all!

Should you let your dog plant a big slurpy kiss on your cheek? Any public health expert will tell you no, but really … you’ll likely be fine.

It’s funny to realize, though, that even when you consider most humans take pride in having kissable breath and most hounds could care less about doggie breath, most people would much rather have a random dog kiss them than be French-kissed by any person they know.

Becker is the resident veterinarian on “Good Morning America.” Spadafori is a syndicated pet columnist. Their two new books, from which these questions are taken, are “Why do Dogs Drink out of the Toilet?” and “Do Cats Always Land on Their Feet?” Look for future dog and cat answers in The (402).