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The Structure of the Nasal Cavities
Unit: Olfactory System

The Structure of the Nasal Cavities

The olfactory system is responsible for the sense of smell. This system detects odours that are inhaled through the nose. The nose has two nostrils which open into two nasal passages which in turn open into the nasal cavity which is situated behind the nose. The nasal passages are separated by the septum. The nasal cavity is connected to the back of the throat. Air is inhaled through the nostrils, it enters the nasal passages, travels through the nasal cavity, then passes into the trachea, then onto the lungs. The inside of the nose is lined with a moist, thin layer of tissue called a mucous membrane.

The Function of the Olfactory Receptors and Recognition of Stimuli by the Brain

This membrane is responsible for warming and moistening the air as well as filtering out dust and germs and any other small particles that might irritate the lungs. The olfactory epithelium, situated high in the roof of the nasal cavity, are specialised cells within the mucous membrane. The olfactory epithelium contain receptor cells which are sensitive to the odour molecules that travel through the air. There are at least 10 million of these receptors in the nose. Once stimulated the receptors send signals via the olfactory nerve to the olfactory bulb. The olfactory bulb is situated just above the nasal cavity. In the bulb, the receptor cell fibres connect with the olfactory nerves sending impulses to the brain which then interprets the smells. The cribriform plate separates the olfactory receptors from the olfactory bulb, they are linked by a series of holes in this plate.

The Mechanism of Smell

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