The Olfactory System

The olfactory system subserves the sense of smell. In humans, it plays an integral role in daily life, for example by imparting much of the "richness" in the flavor of food. In animals, the olfactory system is of critical importance to immediate survival-in tasks such as food selection and predator identification-but it also impacts significantly on social interactions, reproductive function and many other aspects of behavior. The olfactory system can be divided into two main components: (1) the main olfactory system which consists of the main olfactory epithlium in the nasal cavity where transduction of volatile odors occurs, and the main olfactory bulb and its connections with other parts of the brain; and (2) the accessory olfactory system comprised of the vomeronasal organ where transduction of non-volatile pheremones occurs, and the accessory olfactory bulb and its connections with other brain areas. The accessory olfactory system plays a particularly robust role in regulating many aspects of animal behavior, but its function in humans remains conjectural. This chapter reviews anatomical, physiological and functional aspects of these two components of the olfactory system.