The nose knows.

Why do we need our sense of smell?
Though it is not fully understood, the sense of smell is more important than you may think. It is directly related to the sensation of taste, because the brain requires both smell and taste to be able to distinguish most flavors. 

Olfactory nerve cells (smell receptor cells) are located in the upper nasal cavity and connect directly to the brain. These nerve cells have tiny cilia (like tiny little hairs) that are stimulated by different chemicals in the odors around us. When stimulated, the cilia send nerve impulses to the brain, and the brain perceives the smell. 

Research indicates that people who have a diminished or lost sense of smell experience a reduced appetite and food "just doesn't taste right." This can affect our enjoyment of eating, socializing and quality of life. 

Our sense of smell also alerts us to potential harm, such as a fire, hazardous chemicals or gases, and spoiled food. (Click here for one patient's story.) For these reasons, a sense of smell and taste is especially important for people who work in certain fields, such as cooking or fire protection.

Why do we have sinuses?
The main purpose of the sinuses is not fully understood. Some experts maintain that they exist to lighten the weight of the skull, while others note that the sinuses improve the resonance of your voice. 

Another theory claims the sinuses are there to ensure that, in the event of severe trauma, the facial skeleton will crumple and collapse in order to absorb most of the force of the trauma and protect the brain from injury.