Toungue Talk: Anatomy of a Dog's Tongue
By T. J. Dunn, Jr., DVM
It's a radiator, a water-lapper, a healer of wounds, a food conveyor, a register of tastes, a texture sensor, and a wet equivalent of a dog's handshake. A dog's tongue has more responsibilities than any other part of the dog anatomy -- excluding the brain. And oddly enough, for all its duties and actions, it is one of the most maintenance free structures of all the dog's body parts!
Let's take a look at this unique structure and see what we can discover.
On a recent photo shoot with one of my dog trainer/hunter friends, I exposed four rolls of film while he put this three black labs through some off-season training. When I placed the slides on the viewer I was curiously struck by how many action shots captured the charging subjects with their long, flexible tongues literally flopping out there in the breeze. (I'm talking about the dogs here, not the trainer!)
Almost every photo displayed the dog's tongue completely extended with mouth open wide, fully exposing the airway to the onrushing breeze. After seeing these photos, I was amazed that in my busy small animal practice I wasn't seeing more than just occasional tongue injuries.
With that fleshy, vascular flag waving around, frequent injuries should be expected -- but in 25 years of practice in an area pleasantly infested with hunting dogs, tongue problems are just not very common.
Nevertheless, it has happened more than a few times that I would get a frantic call at home from a hunter wanting to rush his gun dog in because "she's bleeding from the mouth like a stuck pig!" So I'd rush in to the animal hospital expecting to perform some heroic surgery only to find the bleeding had stopped and the owner apologetic about all the fuss. Upon examining the mouth, I'd find one or more lacerations -- sometimes not very substantial at all -- that had clotted and nicely sealed.
"Keep her quiet today - turn her loose again tomorrow," I'd say to the relieved owner.
What has happened in this situation is that at the time of the injury, whether the tongue was traumatized by thorns or accidentally pierced by a tooth, barbed wire or other sharp object, the tongue was expanded and engorged with blood.
A major source of heat loss for the exercising dog, the tongue's rich supply of blood vessels all dilate, causing the tongue to swell and extend. Even a tiny puncture at this time will reward the insult with a flow of crimson. And a deep cut can produce some truly scary amounts of blood.
When the owner sees blood "all over the place" the hunt stops, the dog cools off, the blood vessels constrict turning down the flow to normal and the tongue shrinks back to a resting state -- perfect condition for clotting to occur.
So, if you find yourself out in the field or marsh and your canine companion cuts his tongue -- stop the activity, cool the dog down with a short swim and allow a few seconds of a cool drink of water; and consider a trip to the vet if your judgment tells you the bleeding is pretty significant. And don't allow the dog to continue to drink!
All that tongue activity required to lap up the water will only delay the clotting. Plus, if some anesthesia and suturing is required, it is preferable to operate on a patient that has an empty stomach rather than to risk anesthesia-induced vomiting in an unconscious patient.
Examining the Tongue's Anatomy
Essentially the tongue is an elongated muscular organ with the top surface covered with specialized epithelium. Its responsibilities include responding to taste, touch, pain, and aiding in heat dissipation.
When I began researching this article, I quizzed myself and was able to recall only three muscle groups interacting with the tongue. Well, the faithful Miller's Anatomy of the Dog describes no less than eight pairs of muscles whose job it is to control the tongue's activities. They have intimidating Latin names such as genioglossus vertical and oblique, hyoepiglottis, and sternohyoideus.
That band of tissue directly under the tongue holding it down. . . that's called the frenulum; you've got a frenulum too, only not quite so well developed.
And something you don't have that the dog does -- feel just under the tip of the dog's tongue running from front to back along the midline, you'll find a firm cartilaginous, almost bony structure. That's called a lyssa. This little device was considered in ancient times to be a cure for various ailments including rabies!
Gosh, medicine has come a long way, hasn't it? Modern medicine has progressed to the point where we at this time don't even have a clue as to what the lyssa is for!
TASTE: In addition to directing the dog to eat rotten garbage and to be repulsed at the taste of woodcock, the canine tongue is capable of discerning sensations of salt, sweet and sour. The sensation of sour is dispersed somewhat evenly over the top of the tongue, salt along the lateral edges and rear of the tongue and sweet along the edges and front of the tongue. Dogs have a finely tuned ability to taste water, and that trick is performed only by the tip of the tongue.
PAPILLAE: These odd projections from the surface of the tongue are of five different types. The slightly shredded look to the front and side of the dog's tongue (especially noticeable in newborn pups) are called marginal papillae and those funny bumpy things on the back of the tongue are vallate. Now the next time you see your buddy curiously peering into his dog's mouth and he suddenly exclaims, "Hey, what the heck are these weird doofangles on Cinder's tongue?", you can tell him they're called papillae and there are five kinds of them and casually walk away.
WHAT MAKES THE TONGUE WET? Every dog has four pairs of salivary glands with tiny drainage tubes transporting the saliva into the mouth. One salivary gland is located just beneath and lateral to the eye underneath the "cheekbone". One gland is situated at the base of the ear-canal cartilage; and one just behind the angle of the jaw and the smallest in front of the angle of the jaw. These glands produce the preponderance of moisture in the mouth, secreting a thick (mucoid) saliva and a watery-thin (serous) saliva. Plus, the surface of the tongue itself harbors numerous tiny salivary glands secreting both serous and mucoid fluid. So the dog's tongue doesn't really sweat, but the net effect of the salivary glands of the tongue amounts to the same thing -- cooling by evaporation.
TONGUE COLORS: Have you ever heard some "dog expert" say, "See that black coloring in there on the dog's tongue? Means he's got some wolf blood in 'em." Duh! All dogs, from Chihuahua's to Bernese Mountain Dogs have, through selective breeding over eons, evolved from a wolf-like common ancestor.
Black pigments (technically a result of microscopic melanin granules) in patches on a dog's tongue, gums and inner lips are common and have no medical significance. That is as long as the dark patches are not raised up higher than the surrounding non-pigmented tissue. If you ever see dark, pigmented tissue anywhere on your dog that actually looks like a bump or is raised up above the neighboring tissue, have your veterinarian examine it. It may be a dangerous form of cancer called melanoma. Another nasty form of cancer accounting for about half of all types found in the tongue is called squamous cell carcinoma. Two other types of cancer of the tongue are granular cell tumor and mast cell tumor. If found early, these may be treatable and complete cures are possible, however, plan on surgery and possible radiation therapy.
INFECTIONS: Because it is so richly supplied by nourishing blood vessels, infections of the tongue are not common. Generally, when they do occur, a foreign body such as a fox tail awn, porky quill, thorn or wood splinter is the culprit and can be removed under anesthesia. (Anyone who lets their dog chew on lumber, please stand up ... uh huh. Okay, everybody can sit down now.) Split firewood and 2x4's sure can make a dog proud and happy, but those woody splinters can wreak havoc in the dog's mouth and gastrointestinal tract. Wood is indigestible, you know. Throw them a tennis ball and forget the timber!
It's a good idea to really examine your dog's mouth routinely -- say every Saturday morning just before you start on those chores you've been putting off. Maybe if you're lucky, you'll find something suspicious requiring an immediate trip to the animal hospital and thereby a legitimate postponement of the chores until the following Saturday!
WIRING: The canine tongue is uniquely constructed to do so many things. And to perform all these diverse and intricate functions the tongue requires five separate pairs of nerves coming directly from the brain through tiny openings in the dog's skull. These are called Cranial Nerves since they do not arise from the spinal cord, but directly from the base of the brain itself. In many an idle moment I've pondered what effect on my shooting success there would be if I had a fancy cranial nerve connected to my right forefinger rather than an ordinary spinal nerve ... hmmm.
Remember, the tongue is king. Everything else in the mouth is an assistant. Keep a close watch, though, for ulcers, bruises or bleeding from the tongue, gums or palate. Check for broken teeth that can irritate the tongue or bumps arising anywhere within the oral cavity. Work your finger under each side of the tongue and force it upward so you can inspect the underside of the tongue. I've found some pretty odd things wedged or otherwise hiding beneath the tongue.
You really should reward that tongue once in while by allowing it a full, wet slap on your face just before its owner bounds off on a walk with you -- just for fun -- no dummies, no whistles, no check cords or leashes. Odds are that the tongue will reward you at the end of your playful excursion.
Image: B Rosen / via Flickr
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