See the bump? This is my dog Rudy’s incisive papilla. Your dog has one, also (humans do, too)! It is a bump (papilla) on the roof of the mouth, behind the top front (incisor) teeth. Its purpose is to transfer odor particulate from the mouth up into vomeronasal organ (often called the Jacobson organ), which passes information on to the amygdala.
The vomeronasal organ works both independently and cooperatively with the dog’s nose: while the nose collects dry particulate in the air, which is interpreted through olfactory sensory cells, the incisive papilla collects wetter particulate and air, then transfers it to the vomeronasal organ. Biologists suspect (but have not yet proven) that that vomeronasal organ also gives “alternative pictures” of the same information, when dry particulate is moistened in the dog’s mouth and then processed through the incisive papilla, and transferred to the vomeronasal organ.
The flehman response: You may notice a dog “engaging” her incisor papilla by lifting her top lip (which partially closes the nostrils) and cycling air through her mouth. It sounds a little like panting, and can look like snarling, but is actually just a way of collecting more information. This is called the flehman response, and usually suggests a higher level of interest or engagement with a particular odor, or set of odors.
We are still learning about the vomeronasal organ, how exactly it works, and the precise mechansims of the incisor papilla. There are several mysteries about the incisor papilla and vomeronasal organ still being researched. For more information, I recommend “Inside of a Dog,” by Alexandra Horowitz.
Thanks to Eileen Anderson for this video of the flehman response!
The Dog Guy 