September 25

Husky. Photo Credit: Clipart.com. Photo Credit: Clipart.com.

Science Fact

A Dog's Sense of Smell

A dog's sense of smell is 10,000–100,000 times as strong as a person's. 

Dogs have evolved to have a strong sense of smell, with approximately 900 genes that code for smell receptors, versus humans, who have fewer than 400. They also have 125–300 million olfactory receptors, compared to our six million.

A dog's nose works differently from a person's, with these differences being crucial to a heightened sense of smell. First, a dog's nostrils are independent from each other. This allows a dog to quickly determine from what direction a scent has come. Second, while a person's scent receptors are located along the passageway air flows through to the lungs, a dog has nasal tissue that channels 12% of air into a separate area at the back of the nose, where mucus helps to trap it. This area is used exclusively to break down the chemical makeup of odors in the air, which is forced through bony structures called turbinates.

Olfactory receptors in the lining of the turbinates recognize the chemicals' molecular shapes and transmit that information to the dog's brain for analysis. The olfactory lobe in a dog is, proportionately, 40 times larger than a person's, and some estimates suggest it may occupy up to a third of the brain's work.

Additionally, a dog also has a unique olfactory organ: the vomeronasal or Jacobson's organ. This organ, located at the bottom of the dog's nasal passage, picks out pheromones, or body scents useful to mating, in the air using receptors that are distinct from those elsewhere in the nose.

Finally, while humans breathe in and out through the same passageway, diluting scents, a dog exhales through the slits on the sides of its nose, leaving scents at full power for longer and stirring the air coming into the nose in such a way as to magnify odor potency. This also lets a dog keep sniffing without the need to stop to exhale.

Humans make use of dogs' exceptional sense of smell by training them to locate missing people, cadavers, drugs, explosives, weapons, tumors, and agricultural items.

Celebrate this and the other amazing abilities of "man's best friend" during National Dog Week, Sept. 24–30. The celebration was first established in 1928 by Will Judy, author of a number of books including The Dog Encyclopedia, publisher of Dog World Magazine, and founder of the Dog Writers Association of America. 2018 marks the 90th anniversary of the celebration.

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