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Dogs are born to sniff

Original Publication Date: February 16, 2015
By C. Sue Furman, Ph.D.

A dog sees the world with their eyes, but their super sense of smell gives them a much more interesting and detailed picture.

Their moist spongy nose catches many scents that humans miss.

Breathing and smelling are two separate functions. Humans have only one air passageway for both.

The dog's nose is much more sophisticated. Their two nostrils breathe independently, and they can even determine in which nostril an odor arrived.

A fold of tissue just inside the dog's nose forms two pathways. Air for respiration takes one path and is sent to the lungs. About 12 percent of the air is meant for smelling and takes the other pathway where several hundred million special olfactory receptor cells detect the many scents as they pass by.

In both human and dog noses, air passes over a labyrinth of bony scroll-shaped plates, called turbinates. Scent receptor cells in the tissues that line the turbinates recognize odor molecules by their shape and send nerve signals to the brain for analysis. In humans, about 5 million scent receptors are concentrated in about one square inch or an area the size of a postage stamp.

If one could unfold the turbinates of a dog, they would cover about 60 square inches or the area the size of a sheet of typing paper. The dog's turbinates contain many millions of receptors. The actual number varies with the breed.

It is estimated that a Dachshund has 125 million nerve endings that sense smells, while a German Shepherd has 225 million and a Bloodhound tips the scale with 300 million scent receptors.

With so much information entering, it is not surprising that the percentage of a dog's brain specialized for analyzing scents is 40 times larger than that of a human, and his sense of smell is 10,000 to 100,000 more acute. You could smell a spritz of perfume in a room. A dog could detect the same spritz of perfume in an enclosed stadium and distinguish the ingredients.

Dogs have a second olfactory capability in the vomeronasal organ or Jacobson's organ located in the bottom of the nasal passage. It detects odorless pheromones that tell a dog if another dog or human is male or female, what they ate, where they have been, what they have touched, and if they are ready to mate.

Human pheromones tell the dog if a person is stressed, ill, happy, or angry.

Dog noses have another unique feature. We exhale air out the same way it came in, which forces out any incoming odors. Dogs exhale through the slits in the side of their nose so new aromas can enter the nostrils.

Humans see and hear a single moment. A dog's sense of smell allows him to perceive a story through time. His nose sees a whole world beyond our eyes.

Sue Furman, Ph.D, has published two books and a DVD on canine massage and teaches classes in pet massage, acupressure, first aid and CPR. See her schedule and submit questions at