Before you can truly appreciate the beauty of a dog's paws, you should first understand their anatomy.
A dog's paws are made up of four digits - the equivalent of the human fingers. The thumb though has been atrophied. Dog paws are also equipped with digital pads, which are different from human finger pads.
Let's take a closer look at each of these parts to gain a better understanding of how a dog walks and uses his paws.
Understanding paw anatomy of your dog is therefore essential for maintaining his healthy life.
Anatomy of Dog Paws
In dogs, the third and fourth digits are the major weight-bearing footpads.
The large, central pad of your dog's front paw is known as the metacarpal pad. The central pad of your dog's rear paw is instead known as metatarsal pad.
These larger-heart shaped paw pads help absorb shock while the dog is walking, and help distribute weight evenly.
A dog's front paws also have a dewclaw, an extra claw on the lower side of the front leg. Some breeds have dewclaws on all four legs.
Some dogs have a significant amount of webbing in between their toes. This webbing helps animals paddle through the water and creates a wide, flat foot. Some dogs have all the webbing, while others only have a small amount.
Breeds with webbed feet include the Portuguese water dog, Chesapeake Bay retriever, and Redbone Coonhound. Other breeds with webbed feet include the German short-haired pointer, Portuguese water dog, and Newfoundland.
Dog Paw Pad Material
What are paw pads made of? Dog paw pads are made of thick layers of fat and connective tissue.
The dog's paw pads outer surface consists of the thickest and toughest skin of the dog's body.
All in all, a dog's paw pads are composed by five layers of skin, with the stratum corneum being the thickest layer of all the others combined.
Paw pads in dogs are meant to absorb shock and support the weight of the dog while walking and cushion its joints and bones.
The pads help attenuate the force of the foot making contact with the ground along with protecting the dog's musculoskeletal system since they're the only dog body parts making direct contact with the ground.
A study conducted by researchers in Japan showed that dogs have a special thick layer of adipose tissue in their paws, which helps prevent freezing. Furthermore, they have veins that are close to arteries on their footpad, allowing heat to conduct through it.
Presence of Conical Papillae
If you look at the bottom of your dog's metacarpal pad or metatarsal pad, you may notice how the surface is made of several conical papillae. These may smoothen out centrally with lots of walking on rough surfaces and can even become abraded.
"I have seen a few dogs that became very excited while their owners were swimming in the backyard pool. These dogs ran around and around the pool for hours and the paws became abraded," observes Mary Ann Seagren in Clinical Anatomy and Physiology Laboratory Manual for Veterinary Technicians.
Presence of Sweat Glands
The pads also contain eccrine sweat glands, allowing dogs to sweat from their feet, although this isn't part of the dog's primary cooling system.
Paw pads are therefore very important! They provide cushioning, traction, abrasion resistance and protection from freezing temperatures.
Presence of Pacinian Corpuscles
Pacinian corpuscles consist of sensory receptors which allow dogs to feel vibration and deep pressure. The vibrational role may be used by dogs for the purpose of detecting surface texture, for example differentiating between walking over a rough or smooth surface.
They were first found by German anatomist Abraham Vater in 1741, and then rediscovered in 1835 by Pacini.
Anatomy of a Dog's Toes
If we look at the toes of many animals, we may notice that the general standard is to have five toes at the end of a limb.
Humans have 5 toes and so do bears, primates, weasels, bats, and several types of reptiles and birds.
Some animals such as dogs, foxes, wolves and coyotes though have though four fully functional toes instead of five.
What do these four-toed animals have in common?
Fossil evidence shows that animals that show a loss of digits are for the most part animals who were required to maintain high speeds for long distances, explains John Buckwalter, Emeritus of Biology at Alfred State College.
Such animals are known as "cursorial animals" and they are distinguished for their long limbs, shortened digits and reduced number of toes.
In order to become swift runners, a change in basic physiology was necessary so several speed adaptations were necessary.
An extra toe may weigh just a few ounces, but its extra weight on the foot may ultimately have an impact when it's carried along for the ride as an animal runs to catch his dinner or runs for his life.
So evolution decided that it was in the dog's best interest to not have a fully developed 1st digit, which is the equivalent of our thumb.
Reduced weight is also a plausible explanation as to why a dog's legs has concentrated muscle mass at the top, while at the bottom the legs get more slender with a lighter foot.
"An increase in limb length adds to stride length, whereas reduction in limb weight especially distally, enhances stride rate, "says S. M. Kisia in the book "Vertebrates: Structures and Functions."
Anatomy of a Dog's Dewclaw
It would be wrong though to say that the dog has totally lost his fifth toe. In reality, that extra digit is still there, but it's just been reduced.
You may stumble on it if you take a look at your dog's foreleg and notice a claw that's located higher up and that doesn't normally touch the ground as the other toes.
That claw is known as the "dewclaw" and it's a remnant of that original fifth digit dogs used to have in the past. In technical terms, it's a vestigial structure, meaning that it has lost its original function and therefore has atrophied.
It would be wrong though to say that a dog's dewclaws have completely lost their functionality. Turns out, contrary to what we may have heard, those dewclaws at times actually touch the ground, but because it happens when dogs run at high speeds, we hardly ever notice it.
Christine Zink, a veterinarian working with canine athletes, has found that those dewclaws that many people chop off and think of them as useless appendages, actually help prevent torque on the leg especially when the dog is galloping and making tight turns, as often seen in canine sports.
Without the dewclaw, there are risks that leg may twist which over time can lead to problems such as carpal arthritis and other injuries to the dog's elbow, shoulder and toes!
Note: If you don't see this fifth digit on your dog's front feet it likely was removed shortly after birth to give the dog a cleaner look or to prevent it from getting caught on things.
A Lesson in Comparative Anatomy
While us humans and bears are plantigrades, meaning that we place our whole foot on the ground with a rolling heel-to-toe action, dogs are digitigrades, meaning that they only walk on their digits, a quality that makes them faster and quieter runners as their heels are not required to touch the ground, explains Stanley Coren, in the book "Do Dogs Dream? Nearly Everything Your Dog Wants You to Know."
This means that the bones of the dog's wrist (carpals), palm (metacarpals), sole (metatarsals) and ankle (tarsals) are kept off the ground. We therefore make a mistake when we compare our dog's paws with our hands and feet.
In reality, we are mainly looking at their toes as seen in these illustrations. Basically, the bones that correspond to our wrists and ankles are set much higher than we would think which explains why many people often confuse the dog's ankles (tarsal, hock) for the dog's knee (stifle).
- Veterinary Anatomy of Domestic Mammals ,Textbook and Colour Atlas By Horst Erich König, H. Bragulla, Hans-Georg Hans-Georg · 2007
- Colville, T. P., Bassert, J. M. (2009). Clinical Anatomy and Physiology Laboratory Manual for Veterinary Technicians. United Kingdom: Mosby.