Canine olfactory system. Artwork showing the complicated airways inside a dog's nose that allow olfaction (its sense of smell). Shown here is the shape of the airway, which extends from the dog's nostril (naris) to the cranial location above the eye. The cross-section reveals respiratory turbinates in the region of the nose responsible for heating and cooling air breathed in. Further back is the olfactory epithelium, where smells are actually sensed. The dog's brain is behind this. Small chemical molecules in the air (coloured spheres) are drawn in through the nostrils (yellow arrow) to bring them to the olfactory epithelium.