olfactory system, the bodily structures that serve the sense of smell. The system consists of the nose and the nasal cavities, which in their upper parts support the olfactory mucous membrane for the perception of smell and in their lower parts act as respiratory passages.

How does the olfactory system work in humans?

Each olfactory neuron has one odor receptor. Microscopic molecules released by substances around us—whether it's coffee brewing or pine trees in a forest—stimulate these receptors. Once the neurons detect the molecules, they send messages to your brain, which identifies the smell.

How many olfactory systems do humans have?

That sounds obvious, but while humans have sniffed around 3,300 different scents for science — out of the trillions possible — the highest number for animals is 81, by spider monkeys.