Dog Basics

Introduction Dogs are descendants of wolves that

roamed wild over much of the world in ancient times.

Humans have associated with dogs for thousands of years, originally domesticating them as beasts of burden or guard animals.

Today dogs still work but the primary role is that of a loyal companion.

Description and Physical Characteristics

Dogs look very different from humans but share many of the same internal organs such as: Heart (Circulatory System) Lungs (Respiratory System) Monogastric digestive tract

Body Size Dogs come in many shapes and sizes. The smallest breeds include the toy and

miniature varieties such as the Toy Poodle and the Chihuahua.

These dogs usually weigh only 5 pounds. Medium-sized dogs include many terriers

and spaniels which weigh in the 10-50 pound range.

Body Size Larger still, are the retrievers, shepherds

and setters which weigh 65 to 100 pounds.

The Giant breeds such as the Mastiff, Komondor and the Saint Bernard can apprach or exceed 200 pounds.

Metabolism Dogs have a higher metabolism than

people. They breathe faster, pump blood faster,

mature faster, and have a higher normal body temperature than humans.

Young dogs seem to have more energy that children, however, this high metabolism come with a shorter life span.

Dog Years vs Human Years

A common rule of thumb is that 1 dog year equals about 10-12 human years for the first 2 years of life and then 4 people years (per dog year) after that.

Actual life span depends on the health and size, with small breeds generally living longer that larger ones.

Dog Years vs Human Years

Dog Years Human Years6 to 12 months 10 to15 years12 to 18 months 15 to 20 years18 to 24 months 20 to 24 years4 years 32 years6 years 40 years8 years 48 years10 to 12 years 56 to 64 years13 to 14 years 68 to 72 years15 to 20 years 76 to 96 years

Temperature Regulation Dogs are generally better at conserving

heat than cooling themselves. The fur acts a blanket, thus insulating

and retaining heat generated by metabolism.

Dogs cannot sweat but instead loose heat through panting

Temperature Regulation The rapid breaths (in panting) are an

attempt to lose heat through evaporation by moving hot, moisture filled air in and out.

During panting, little air can be exchanged in the lungs and a dog must periodiocally stop panting and take a good respiratory breath.

Temperature Regulation Drinking water can also help cool dogs

down. Because the cooling system for dogs is

relatively poor, hot, humid summer situations can be life threatening.

Measures should be taken to cool them (AC, misters, wade pool, etc)

The Senses Dogs have the same 5 senses that

people have, but to very different degrees.

The Senses: Sight Dogs can see movement and light much

better than humans. Dogs have more of a specific type of cell

called a rod, which is good at collecting dim light.

This gives them better night vision

The Senses: Sight A reflective layer in the eye, called the

tapetum lucidum, magnifies incoming light.

This layer is what gives the eye a blue/green tint when a light is shined in the eye.

The Senses: Sight

The Senses: Sight Dogs do not have as much visual acuity

as humans. (They cannot distinguish fine details)

Dogs cannot differentiate colors as well as humans because they have fewer cells in the retina called cones, which are responsible for color vision.

The Senses: Sight A unique feature of the dog eye is the

nictitating membrane. (third eye) This additional eyelid is whitish pink in

color and is found under the other eyelids in the inside corner (near nose) of the eye.

The third eyelid extends up when needed t protect the eyelid from scratches or in response to inflammation.

The Senses: Sight Nictitating Membrane

The Senses: Hearing The ear canal of the dog is much deeper

that that of humans and creates a better funnel to carry sound to the ear drum.

The average dog can hear 4 times better than the average human.

Dogs are better at distinguishing the direction of sound. (adaption useful for hunting)

The Senses: Hearing

The Senses: Hearing Unfortunately, the deeper ear canal

predisposes dogs to ear problems. Grease, wax and moisture buildup can

lead to inflammation and infection. Floppy ears or hair within the ears can

exacerbate the problem limiting ventilation.

The Senses: Smell & Taste

Dogs have an extraordinarily acute sense of smell, about a million times more sensitive than that of humans.

They can detect odors at extremely low levels and differentiate.

The Senses: Smell & Taste

Odor molecules dissolve in the moisture that coats the inside of the canine nose.

Signals are then sent from the olfactory membranes in the nose to the olfactory center of the brain which is 40 times bigger in dogs than in humans.

The Senses: Smell & Taste

Dogs have the vomeronasal organ on the roof of their mouth that allows them to “taste” certain smells.

Dogs however, have about 1/6 the number of taste buds when compared to humans and have a poor sense of taste.

Locomotion Dogs have the same muscles, tendons,

joints, and ligaments as people and all 4 limbs are maximized for locomotion.

In gait comparision, dogs move much like the horse (walk, trot, canter, gallop)

The canine bones that are comparable to the long bones of our hands and feet are located in the dogs lower legs.

Locomotion The angular hock in the hind legs in

comparable to the ankle in people.

Pads and Nails The canine paw contains specialized

structures that help the animal move over different surfaces.

The bottom of the paw is covered by thick, resilient pads that become callused after years of steady wear.

These pads protect the paw and help provide a secure grip on many types of surfaces.

Pads and Nails The toenails provide traction while

running and are used for digging. Canine toenails are thick, brittle

structures made up of a protein called keratin.

A large blood supply runs down the middle and feeds the cuticle (quick) of the growing nail.

Pads and Nails Dogs have rudimentary equivalents of

human thumbs called dew claws that are found on the middle side of the front paws or lower legs.

Dew claws have no function They are commonly removed when the

animal is a puppy or when spayed or neutered.

Skin and Hair Canine skin has several layers, including

an outer epidermis that is constantly being replaced and an inner dermis that contains nerves and blood vessels.

Canine skin is thinner and much more sensitive than humans.

Dogs should only be shampooed with products that are made for dogs.

Skin and Hair Canine fur grows from hair follicles in the

skin. Dogs have compound hair follicles, with a

central (guard) hair surrounded by 3 to 15 secondary hairs growing out of the same pore.

Sebaceous (oil) glands within the skin lubricate the hair, keeping the coat shiny and water resistant.

Skin and Hair The main function of the hair coat is to

protect the skin and to help regulate temperature.

Fur traps air which provides a layer of insulation against the cold.

Teeth and Mouth Dogs are carnivores with teeth designed

for rending and tearing meat. They have 28 deciduous (baby) teeth

that are replaced by 42 permanent (adult) teeth between 2 and 7 months of age.

Teeth and Mouth The front teeth, which include 12 incisors

and 4 large canine teeth are designed for grasping and tearing.

The rearward premolar and molar teeth grind food into smaller pieces that can be swallowed.

Teeth and MouthType of Tooth Number

(Upper/Lower)Age (Months) at Eruption

Function

Incisors 6/6 2 to 5 GraspingCanines 2/2 5 to 6 TearingPremolars 8/8 4 to 6 GrindingMolars 4/6 4 to 7 Grinding

Digestive and Urinary Tracts

The gastrointestinal tract includes the stomach, the small intestine, and the large intestine (colon).

This system digests food in to useful nutrients, absorbs water and eliminates waste.

Digestive problems show up as vomiting or diarrhea, which can have many causes: Stress Worms Ingestion of bones, sticks, or other foreign material

Digestive and Urinary Tracts

The urinary system eliminates nitrogenous wastes from protein breakdown and helps control fluid levels.

Waste products are filtered by the kidneys and then sent through the ureters t the urinary bladder for storage.

Urine is passed out of the body by the urethera.

Anal Glands Rump rubbing or “scooting” is usually

associated with impacted anal glands. The anal glands are located in the 4 and

8 o’clock positions around the anus. These scent glands contain a foul

smelling secretion that is normally expressed during a bowel movement.

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Anal Glands The secretions often thicken which can

plug the duct, causing pressure and irritation that can lead to infection.

Many dogs need to have their anal glands manually emptied by their veterinarian on a regular schedule.