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Everyone knows dogs have a better sense of smell than humans. But here at the Dolce Vita doggie blog, we always want to know not just what but why. Thanks to Newsday for the informative article giving us what we want:
Sniff sniff sniff.
You can actually see a dog's nose hard at work, picking up a scent wafting through the air, following the invisible trail a rabbit left in the yard, or investigating your pants leg for evidence of a secret meeting with a cat.
No one knows for sure how much more scent-sensitive dogs are than humans: a thousand times? Ten thousand?
But what is known is that a dog's nose has many more odor receptors, and an olfactory (smell) center that takes up much more room in the brain.
Human beings have about 5 million odor receptors, while dogs, depending on the breed, may have more than 220 million. The small human nose devotes only a postage stamp-sized area to odor receptors.
The average dog nose has a mucous-y scent receptor area which, if spread out, would cover a Kleenex tissue. A dog's nose - moist on the outside, as well as the inside - acts as a magnet to scent molecules in the air and on the ground.
Sniffing - a string of quick inhales and exhales - helps a dog rapidly identify a scent. Each deliberate sniff widens the dog's nostrils, allowing him to pull in more scent-laden air.
According to researchers, a sniff also temporarily straightens the dog's nasal cavity, allowing odor molecules to proceed directly to receptors deeper in the nose.
The contact between molecules and receptors generates nerve impulses, which travel along the olfactory nerves to the brain's huge smell center.
Presto: Scent decoded.
(Meanwhile, Jacobson's organ, a special chamber above the roof of a dog's mouth, has its own scent receptors. These transmit nerve impulses to the brain's hypothalamus, an area associated with social and mating behavior.)
The average dog's ability to detect a few scent molecules in a trillion others has created a whole industry built on canine noses.
Dogs sniff for hidden drugs in cars and planes, follow the trails of hikers missing in the woods, and find the remains of people in the rubble left behind by earthquakes and bombings.
Now, scientists are testing the ability of dogs to detect the distinctive smell markers of various cancers.
So far, it seems that dogs are good at detecting melanoma, the deadliest skin cancer. Dogs also have been trained to detect the waste products of lung and breast cancer cells, simply by sniffing a patient's breath. And some dogs can identify people with bladder or prostate cancer by picking up on odors in urine.
Dogs trained to detect certain cancers, scientists say, might someday help screen whole villages of people in remote areas without easy access to lab tests.
A dog's sensitivity to scents can even be used to calm it down, in a kind of canine aromatherapy.
Researchers in Northern Ireland found that dogs riding in a car filled with the odor of lavender spent more time sitting quietly, less time racing from window to window and yapping in the driver's ear.
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More links on the same subject:
Video of a dog's nose in action (from SciencCentral News)
An article from MSNBC.com about dog's potentially diagnosing cancer by smell. Really.