Air enters the nose via the nostrils.
The lungs draw air into the body via the nose and mouth. As air enters through the nostrils, it flows through long hairs which trap large particles. Inside the nasal cavity, odor molecules hit the olfactory epithelium on the roof to send the brain scent signals. Tiny hairs called cilia and mucus grab foreign matter missed by the larger hairs inside the nostrils. At the back of the nasal cavity, the air gets pulled into the larynx and down to the lungs.
Odor molecules from freshly baked cookies send signals to the brain via the nose.
Inside the nasal cavity, sensory organs called olfactory epithelium detect odor molecules carried in the air. When they do, they send a signal to the brain via the olfactory nerve and olfactory bulb. The brain then translates those signals into reactions learned from previous exposures to smells.
