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Olfactory nerve (CN I)

Learning objectives

After working through this study unit you will be able to:

  1. Describe the structure, function and relations of the olfactory nerve.
  2. Discuss the olfactory pathway and make-up of the olfactory mucosa.

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The olfactory nerve (CN I) is a special sensory (special visceral afferent [SVA]) nerve that carries the sensation of smell (olfaction) via a series of nervous structures, which make up the olfactory pathway to the brain. This allows us to detect various odors. Each olfactory nerve proper is actually one of 15-20 olfactory fiber bundles, which consist of bipolar olfactory sensory neurons located in the olfactory mucosa of the roof of the nasal cavity. These fiber bundles course through small tiny foramina in the cribriform plate of the ethmoid bone to enter the cranial cavity, where they join the olfactory bulb.

In the olfactory bulb, the olfactory nerve fibers synapse with primary dendrites of projection neurons (known as mitral and tufted cells) to form an olfactory glomerulus. Axons from these neurons project posteriorly as the olfactory tract. As it courses posteriorly, each olfactory tract bifurcates at the olfactory trigone into the medial and lateral olfactory striae. The olfactory striae project into areas of the olfactory cortex, allowing perception of smell. The olfactory bulb also receives efferent fibers which synapse on granular cells and subsequently interact with mitral and tufted cells to modulate the sensation of smell.

This video will help you learn more about the olfactory nerve and olfactory pathway.

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Test your knowledge with our quiz on the olfactory nerve and related structures:

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Browse atlas

Take a look at our atlas galleries to further review the structures of the olfactory pathway, as well as the microscopic anatomy of the olfactory organ and bulb.


Key points about the olfactory nerve and pathway
Olfactory organ (Olfactory part of nasal mucosa)
Olfactory sensory/receptor neurons (contain olfactory cilia), supporting cells, and basal (stem) cells
Lamina propria:
Olfactory glands (Bowman's glands)
Olfactory nerve Cranial nerve I (CN I): Collective term for 15-20 olfactory fiber bundles which cross the cribriform plate on each side
Olfactory bulb Contains olfactory glomeruli, cell bodies of projection neurons (mitral and tufted cells), granule cells, periglomerular cells; serves as a relay station of the olfactory pathway
Olfactory tract Axons of projection neurons (afferent fibers of olfactory bulb)
Anterior olfactory nucleus
Efferent (centrifugal) fibers of olfactory bulb
Olfactory striae Medial and lateral divisions of olfactory tract
Olfactory cortex Medial olfactory stria: Subcollosal area, paraterminal gyrus, anterior commissure
Lateral olfactory stria:
Olfactory tubercle, piriform cortex, anterior cortical amygdaloid nucleus, periamygdaloid cortex, and lateral entorhinal cortex
Function/type of fibers Smell/olfaction
Special sensory/special visceral afferent

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