Dog anatomy comprises the anatomical studies of the visible parts of the body of a canine. Details of structures vary tremendously from breed to breed, more than in any other animal species, wild or domesticated,[1] as dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail.[2] The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.[3] Dog lifespan is 10 -13 years.
- Physical characteristics
Like most predatory mammals, the dog has powerful muscles, a cardiovascular system that supports both sprinting and endurance, and teeth for catching, holding, and tearing.
The dog's ancestral skeleton provided the ability to jump and leap. Their legs can propel them forward rapidly, leaping as necessary to chase and overcome prey. Consequently, they have small, tight feet, walking on their toes (thus having a digitigrade stance and locomotion); their rear legs are fairly rigid and sturdy; the front legs are loose and flexible, with only muscle attaching them to the torso.
The dog's muzzle size will come with the breed. The sizes of the muzzle have different names. Dogs with longer muzzles, such as the German shepherd dog, are called mesocephalic and dogs with a pushed in muzzle, such as the pug, are called brachacephalic.
All dogs (and all living Canidae) have a ligament connecting the spinous process of their first thoracic (or chest) vertebra to the back of the axis bone (second cervical or neck bone), which supports the weight of the head without active muscle exertion, thus saving energy.[4] This ligament is analogous in function (but different in exact structural detail) to the nuchal ligament found in ungulates.[4] This ligament allows dogs to carry their heads while running long distances, such as while following scent trails with their nose to the ground, without expending much energy.[4]
Although selective breeding has changed the appearance of many breeds, all dogs retain the basic characteristics of their ancestors. Dogs have disconnected shoulder bones (lacking the collar bone of the human skeleton) that allow a greater stride length for running and leaping. They walk on four toes, front and back, and have vestigial dewclaws on their front legs and on their rear legs. When a dog has extra dewclaws in addition to the usual one the rear, the dog is said to be "double dewclawed".
The dog's ancestor was about the size of a Dingo, and its skeleton took about 10 months to mature.[citation needed] Today's toy breeds have skeletons that mature in only a few months, while giant breeds such as the Mastiffs take 16 to 18 months for the skeleton to mature. Dwarfism has affected the proportions of some breeds' skeletons, as in the Basset Hound.
- Size
Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail.[2] The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.[3]
Researchers have identified a particular piece of genetic material that is common to every small-dog breed and, in turn, is probably responsible for making them tiny. The study, published in 2007, found a regulatory sequence (not in the coding sequence) next to the gene IGF1; together the gene and regulatory sequence are known as a haplotype that "is a major contributor to body size in all small dogs." Medium and large size dogs do not usually have the regulatory sequence, although the small-size sequence was found in the Rottweiler breed. The study included 3,241 dogs from 143 breeds. The researchers concluded the genetic instructions to make dogs small must be at least 12,000 years old, and it is not found in wolves.[5] Another study has shown that lap dogs (small dogs) are among the oldest dog types.[6]
Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Dogs are predators and scavengers, possessing sharp teeth and strong jaws for attacking, holding, and tearing their food. Although selective breeding has changed the appearance of many breeds, all dogs retain basic traits from their distant ancestors. Like many other predatory mammals, the dog has powerful muscles, fused wristbones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
- Temperature regulation
Primarily, dogs regulate their body temperature through panting,[37] and sweating via their paws. Panting moves cooling air over the moist surfaces of the tongue and lungs, transferring heat to the atmosphere.
Dogs and other canids also possess a very well-developed set of nasal turbinates, an elaborate set of bones and associated soft-tissue structures (including arteries and veins) in the nasal cavities. These turbinates allow for heat exchange between small arteries and veins on their maxilloturbinate surfaces (the surfaces of turbinates positioned on maxilla bone) in a counter-current heat-exchange system. Dogs are capable of prolonged chases, in contrast to the ambush predation of cats, and these complex turbinates play an important role in enabling this (cats only possess a much smaller and less-developed set of nasal turbinates).[38]:88 This same complex turbinate structure help conserve water in arid environments. The water conservation and thermoregulatory capabilities of these well-developed turbinates in dogs may have been crucial adaptations that allowed dogs (including both domestic dogs and their wild prehistoric ancestors) to survive in the harsh Arctic environment and other cold areas of northern Eurasia and North America, which are both very dry and very cold.[38]:87
How do dogs breathe?
A dog breathes only through the nose. This is the misconception of a lot of dog owners. It is also believed that dogs can’t breathe through the mouth as the mouth is only used by the dog to pant and not to breathe. Panting though is a form of heavy breathing. Dogs have no sweat glands and when they are hot or when their heart rate is elevated they will disperse the body heat by hanging out their tongue to pant. Yes, dogs breathe through their noses but not all the time. Like humans dogs breathe both through the nose and the mouth. Have you noticed how your throat gets dry when you breathe through your mouth because your nose is stuffed or blocked because of a cold? Pretty much the same thing happens to a dog. To prove that dogs also breathe through the mouth try holding out your hand on the dog’s mouth and you will feel the dog’s warm breath. Although in most cases breathing is done through the nose breathing can be done using both the mouth and the nose at the same time. This breathing technique that is known as circular breathing or cyclical breathing is a learned thing that is most commonly used by wind instrument players. A dog that has been doing a strenuous exercise or one that is panting is breathing in this manner.
The nasal cavity is composed of mucus membranes that serve as filters that stop dirt and germs from getting into the lungs. The same is true in canines although canine noses are far more sensitive than human’s. Dogs have heightened sense of smell because their olfactory bulbs are at least four times bigger than what we humans have. A dog breathes through the nose as by doing so they can sniff not only interesting smells but they can also track and scent a prey. Because of this ultrasensitive sense of smell, dogs are predisposed to breathing through their noses when sleeping. Seldom would you see sleeping dog breathing through the mouth. By breathing through the nose a sleeping dog can detect the detect the presence of predators. Canine noses are different from human noses in design. Notice the slits on the sides of a dog’s nose. This is where exhaled air is released so that it would not taint or pollute the air being inhaled into the nostrils. The nostrils are opened and widened when the dog is tracking or trying to sniff a scent.
A dog’s nose is very sensitive. Breeds with long noses are known to breathe easier than short nosed breeds. The Pug, boxer, Shih Tzu and Boston Terrier are only some of the brachycephalic breeds that are noted to have breathing problems. As mentioned a dog would breathe through the nose and through the mouth. But when you noticed the dog breathing only through its mouth there may be some nasal problems. Dogs have the propensity to sniff and it is possible that the nasal area is blocked by a foreign object. The dog may also have nasal tumor. The dog may have stenotic nares. These are obstructed or abnormally narrow and constricted nostrils that makes breathing through the nose difficult. A dog with this type of disorder would breathe through the mouth as breathing through the nose would naturally be unproductive. This disorder can be detected easily as the dog would make wheezing sounds when it breathes through the nose. This disorder can be easily corrected with surgery.
Interesting Fact: Bad Breath in Dogs
We all know bad breath -- also known as halitosis -- when we smell it. Bad breath is the result of a build-up of odor-producing bacteria in your dog’s mouth, lungs, or gut. Persistent bad breath can indicate that your dog needs better dental care or that something is wrong in his gastrointestinal tract, liver, or kidneys. In all cases, halitosis is a red flag that should be investigated.
What Is Bad Breath Caused By?
Most often, canine bad breath is caused by dental or gum disease, and certain dogs -- particularly small ones -- are especially prone to plaque and tartar. However, persistent bad breath can also indicate larger medical problems in the mouth, respiratory system, gastrointestinal tract, or internal organs.
How Can I Determine the Cause of My Dog’s Bad Breath?
Your veterinarian is the best person to pinpoint the cause. A physical examination and laboratory work may be performed. Be ready to answer questions about your dog’s diet, oral hygiene, exercise habits, and general behavior.
When Is It Time To See the Vet?
If your dog’s breath suddenly has an unusual smell, please consult your veterinarian. The following cases can signal medical problems that need immediate treatment.
-
Unusually sweet or fruity breath could indicate diabetes, particularly if your dog has been drinking and urinating more frequently than usual.
-
Breath that smells like urine can be a sign of kidney disease.
-
An unusually foul odor accompanied by vomiting, lack of appetite, and yellow-tinged corneas or gums could signal a liver problem.
How Is Bad Breath Treated?
Treatment depends on your vet’s diagnosis. If plaque is the culprit, your dog might require a professional cleaning. If it’s an issue of diet, you might have to change your dog’s regular food. If the cause is gastrointestinal or an abnormality in your dog’s liver, kidneys, or lungs, please consult your vet about steps you should take.
How Can I Prevent My Dog From Having Bad Breath?
Many people assume that bad breath in dogs, especially at a certain age, is a “given.” But that’s not the case. In fact, being proactive about your pup’s oral health will not only make your life together more pleasant, it’s smart preventive medicine.
-
Bring your dog in for regular checkups to make sure he has no underlying medical issues that may cause halitosis.
-
Make sure your vet monitors and tracks the state of your dog’s teeth and breath.
-
Feed your dog a high-quality, easy-to-digest food.
-
Brush your dog’s teeth frequently -- every day is ideal. (Please be sure to use toothpaste formulated for dogs as human toothpaste can upset a canine’s stomach.)
-
Provide hard, safe chew toys that allow your dog’s teeth to be cleaned by the natural process of chewing.
-
Give your dog well-researched treats formulated to improve breath odor.
-
Discuss home-use oral health products with your veterinarian to see if there’s a type he or she recommends.
Life span
In general, small dogs enjoy longer lives than do their larger counterparts. A recent analysis of veterinary records revealed that dogs under 20 pounds had an average lifespan of 11 years while those over 90 pounds typically lived for only 8 years. Medium and large dogs fell in the middle at around 11 years.