Dogs have a huge olfactory lobe that helps them process all of the scent-related information that they take in. The size and complexity of this structure in the brain is one reason that dogs have such an amazing sense of smell and can detect bombs, cancer, drugs, lost people and even the tiniest trace of dog treats that I’ve accidentally left in my work bag. The dog brain is only one part of the anatomy responsible for their extraordinary sniffing abilities. The canine nose also contains key features that contribute to dogs’ superior skill at smelling, but only recently have people studied how the structures in the nose develop.
The olfactory epithelium is a specialized tissue that lines the nasal cavity. It contains olfactory neurons—the cells that actually detect odors. There is a correlation across species between the surface area of the olfactory epithelium and olfactory abilities. Humans have around 10 square centimeters of this tissue lining the roof of the nasal cavity. Dogs have about 170 square centimeters of it. In dogs, the olfactory epithelium is sprawled out over a craggy, mazelike set of projections that folds and curls within the dog’s nose. The projections are bony structures called turbinates. A recent study explored the development of the canine olfactory epithelium and the turbinates.
In a paper called “FGF20-Expressing, Wnt-Responsive Olfactory Epithelial Progenitors Regulate Underlying Turbinate Growth to Optimize Surface Area”, graduate student Lu M. Yang and several collaborators report that a recently discovered type of stem cell (FEP) controls the extent of the surface area of the olfactory epithelium. These stem cells signal the turbinates to grow by sending out a molecule specific to this purpose. The type and extent of this signaling regulates the final surface area of the olfactory epithelium. Without these molecular signals, the growth of the turbinate and the olfactory epithelium are stunted.
The growth of the olfactory epithelium and the underlying turbinates are part of what allows dogs to have their extraordinary sense of smell. Knowing how these structures develop is an important step towards further understanding how dogs developed such incredible olfactory abilities.
No matter how much scientists learn about canine olfaction, I will still affectionately refer to dogs as “noses with paws”. That sounds so much better than “olfactory epithelia and turbinates with paws”.