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Why Dogs Have a Better Sense of Smell Than Humans

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A dog smelling

Scientists have discovered clues to the differences in scent ability between humans and dogs.

The olfactory epithelium in both species plays an important role in the sense of smell, per a study published in Developmental Cell. In humans, the olfactory epithelium is a single flat sheet lining the roof of the nasal cavity. In dogs, it is a complex maze that curls over a number of bony protrusions (turbinates). The researchers believe that this complexity is what produces the variety in scent ability.

"We think the surface area of the sheet matters in how well animals smell and in the types of smells they can detect," said David M. Ornitz, Ph.D., professor of developmental biology for Washington University School of Medicine. "One reason we think this stems from differences in the complexity of these turbinates. Animals that we think of as having a great sense of smell have really complex turbinate systems."

The Role of Stem Cells in Smell

Scientists recently began to piece together the link between stem cells and the olfactory epithelium.

In the study, Lu M. Yang, a graduate student in Ornitz's lab, found that stem cells, dubbed FEP cells, control the size of the olfactory epithelium's surface area and signal growth to the molecules beneath the turbinates. When the stem cells can no longer signal, turbinates and the epithelium surface experience an arrested development. This can account for the differences in the epithelium surface across different species. Further studies with mice can help examine the complexity of olfactory systems and how they impact a species' sense of smell.  

"Before our study, we didn't know how the epithelium expands from a tiny patch of cells to a large sheet that develops in conjunction with complex turbinates," Yang said. "We can use this to help understand why dogs, for example, have such a good sense of smell. They have extremely complex turbinate structures, and now we know some of the details about how those structures develop."