Sniffing Your Way to Better Hospital Experiences – Materials

5 - Designed to Sniff - Turbinates

Designed to Sniff – Turbinates

In humans, the sense of smell is relegated to a small region on the roof of our nasal cavity, which happens to be along the main airflow path. So the air we smell just goes in and out with the air we breathe. When we inhale, we smell and breathe through the same airways within our nose. We can’t wiggle our nostrils independently. Dogs can. When dogs inhale, a fold of tissue just inside their nostril helps to separate these two functions.

Dr. Brent Craven, a bioengineer at Pennsylvania State University who modeled airflow and odor transport using high-resolution MRI scans of the canine nose found that when airflow enters the nose it splits into two different flow paths, one for olfaction and one for respiration. Craven’s team also found that in dogs about 12 percent of the inspired air, detours into a recessed area in the back of the nose that is dedicated to olfaction, while the rest of the incoming air sweeps past that recess and flows down through the pharynx to the lungs. Within the recessed area, the air filters through a labyrinth of scroll-like bony structures called turbinates that sieves odor molecules based on different chemical properties. Olfactory receptors within the turbinates, in turn, “recognize” these odor molecules by their shape and dispatch electrical signals to the brain for analysis. Craven and colleagues are working to reverse-engineer the canine nose, in part to aid in the design of artificial “noses” that can sniff out odors with the same level of acuity as our canine companions. (Craven, 2010)

A dog can even smell adrenaline and pheromones that we cannot; this allows them to anticipate a fight or flight response from a person or another dog before we have a clue.

In his book The Dog’s Mind, Dr. Bruce Fogle cites studies from the 1970’s that showed dogs can detect butyric acid – one of the components of human perspiration – at up to a million times’ lower than we can. (Fogle, 1990)

Although it should be noted – a dog cannot rationalize and distinguish why a person is emitting adrenaline in their presence. It may be that the human is terrified of dogs, but the dog won’t know this, only that this person is gearing up to fight or flee and should be carefully watched for any sign of an attack. The dog’s olfactory system appears to be more sensitive than anything we can replicate with modern technology.

With this keen sense of smell, dogs have a remarkable ability to detect and discriminate scents. As such, this has enabled dogs to be trained as service dogs for detecting drugs, explosives, landmines, agricultural products, and even more esoteric things like bedbugs and termites. Recently, dogs have been used to identify criminals via a process called a “scent lineup” and are able to locate everything from forensic cadaver material to disaster survivors buried underneath piles of rubble.

(Craven, 2010) Craven, B.A. et al. 2010. “The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of macrosmia.” Journal of the Royal Society Interface, 6 June 2010, 7(47): 933-943.
(Fogle, 1990) Fogle, B. 1990. The Dog’s Mind: Understanding Your Dog’s Behavior. MacMillan.