Anatomy of Smell

Olfaction

• Sense of smell receptors located in superior and middle nasal conchae of ethmoid bone and upper part of nasal septum
• Three types of cells:
  • Supporting cells: form columnar epithelium of mucous membrane lining the nose
  • Olfactory cells: neurons with axon and dendrite, dendrite terminates in 6-8 cilia (olfactory hairs) that react with odors and stimulate olfactory cells
  • Basal cells: produce supporting cells

Conditions for Smelling

• Substance must be capable of becoming a gas or in the form of gaseous particles to enter nostrils
• Substance must be water-soluble to dissolve in nostril mucus and contact olfactory cells
• Substance must be lipid-soluble to pass through plasma membrane of olfactory hairs and initiate impulse

Olfactory Pathway

• Axons of olfactory cells unite to form olfactory nerve
• Olfactory nerve passes through cribriform plate of ethmoid bone
• Terminates in olfactory bulbs (two masses of gray matter beneath frontal lobe)
• Dendrites of neurons in bulbs synapse with axons of olfactory nerve
• Olfactory tract conveys impulses to primary olfactory area of cerebral cortex, where odors are interpreted

Smell Perception

• Smell part of brain in limbic region, connected to frontal lobe where feelings and memory are processed
• Odor particles drift into nose and cause smell receptors to send messages to brain

This quiz covers the structure and function of the sense of smell, including the types of cells involved in olfaction.