Given your enthusiastic interest in the philtrum we posted about not that long ago, we think you’ll REALLY like the Alar Fold.

When a dog inhales, the “alar fold” opens up to allow air to rush up the dog’s nasal cavity so it can bombard her scent receptor cells with odors. From there, the scent cells carry chemical signals to her olfactory bulb, the part of her brain that analyzes those odors.

Conversely, when she exhales, the alar fold closes off the upper part and pushes air down and out through the lateral slits so that the resulting tiny wind currents coming out of her nose stir up even MORE interesting smells. You know this is happening when your dog is sniffing the ground and small puffs of dust rise up from the ground. This is very cool and we want you to look for it because, well, it’s really cool.

What makes all this REALLY cool is that when she does this for the expressed purpose of sniffing, the process is different from when she’s just breathing normally. Her alar fold is what allows air to flow through the upper area of her nasal passages. A bony pocket up there traps the smelly molecules so they can get dissolved in mucous covered scent receptors (ok, snot). This chemical change is what signals the receptor along her olfactory nerve to the olfactory bulb at the end of each nasal passage.

Your dog is a smelling machine, so the next time you’re praising him or her, be sure to tell him or her what a magnificent alar fold he or she has.

Nose image is from Wikicommons. Yellow arrow isn’t.