Olfactory epithelium

Source: Wikipedia, the free encyclopedia.
Olfactory epithelium
olfactory placode and neural crest
SystemOlfactory system
NerveOlfactory nerve
Identifiers
THH3.11.07.0.01001
FMA64803
Anatomical terminology]

The olfactory epithelium is a specialized

smell
. In humans, it measures 5 cm2 (0.78 sq in)[1] and lies on the roof of the nasal cavity about 7 cm (2.8 in) above and behind the nostrils.[2] The olfactory epithelium is the part of the olfactory system directly responsible for detecting odors.

Structure

Olfactory epithelium consists of four distinct cell types:[3]

Olfactory sensory neurons

The

mitral cells in the glomeruli of the olfactory bulb
.

Supporting cells

Analogous to neural

c-KIT cell surface protein.[6]

Basal cells

Resting on or near the basal lamina of the olfactory epithelium, basal cells are stem cells capable of division and differentiation into either supporting or olfactory cells. While some of these basal cells divide rapidly, a significant proportion remain relatively quiescent and replenish olfactory epithelial cells as needed. This leads to the olfactory epithelium being replaced every 6–8 weeks.[7]

Basal cells can be divided on the basis of their cellular and histological features into two populations: the horizontal basal cells, which are slowly dividing reserve cells that express p63; and globose basal cells, which are a heterogeneous population of cells consisting of reserve cells, amplifying progenitor cells, and immediate precursor cells.[8]

Brush cells

A

brush cell is a microvilli-bearing columnar cell with its basal surface in contact with afferent nerve endings of the trigeminal nerve
(CN V) and is specialized for transduction of general sensation.

Olfactory (Bowman's) glands

Tubuloalveolar serous secreting glands lying in the lamina propria of the olfactory mucosa. These glands deliver a proteinaceous secretion via ducts onto the surface of the mucosa. The role of the secretions are to trap and dissolve odiferous substances for the bipolar neurons. Constant flow from the olfactory glands allows old odors to be constantly washed away.[5]

Development

olfactory ensheathing cell

The olfactory epithelium derives from two structures during

embryonic development: the olfactory placode, which was long believed to be its sole origin; and neural crest cells, whose contributions have been identified more recently through fate mapping studies.[9]

The embryonic olfactory epithelium consists of fewer cell types than in the adult, including apical and basal

gonadotropin-releasing hormone neurons form a "migratory mass" that travels towards the olfactory bulb.[9][10] At the end of the embryonic stage, the epithelium develops into a pseudostratified columnar epithelium and begins secondary neurogenesis.[9]

Olfactory placode

FGF8.[14] The resulting regulated downstream expression of transcription factors, such as Pax6, Dlx3, Sox2, and others, within the presumptive olfactory placode are crucial for sub-regionalization within the future olfactory epithelium and is responsible for the diversity of cells that compose the future epithelium.[9][12][15]

Similar to the other embryonic placodes, the olfactory placode gives rise to both neural and non-neural structures, ultimately resulting in the formation of the nasal epithelium.[16] The specification of neural versus non-neural tissue involves signals both within the olfactory placode, and between the olfactory placode and the underlying mesenchymal compartment.[12] Continued signaling by BMP, FGF, and RA, the morphogens that initially induced placode formation, collectively coordinate the patterning of olfactory placode tissue into the future distinct cell types that make up the olfactory epithelium.[16] The cell types derived from the olfactory placode include:[17]

However, there is significant evidence for an additional neural crest-origin for many of these cell types as well.[13]

Olfactory sensory neuron development

transduction proteins on non-motile cilia that extend from the dendritic knob in addition to projecting their axons to the olfactory bulb.[19]

The cells of the olfactory epithelium, including olfactory sensory neurons, begin to

telencephalon.[10] As development of the olfactory pathway progresses, more axons innervate the olfactory bulb, which develops from the rostral-most region of telencephalon. The organization and subsequent processing of odorant information is possible due to the convergence of olfactory sensory neuron axons expressing the same odorant receptors onto the same glomerulus at the olfactory bulb.[21]

Clinical significance

The olfactory epithelium can be damaged by inhalation of toxic fumes, physical injury to the interior of the nose, and possibly by the use of some nasal sprays. Because of its regenerative capacity, damage to the olfactory epithelium can be temporary but in extreme cases, injury can be permanent, leading to anosmia.

Additional images

  • Composition of the Olfactory receptor neuron (captions in German)
    Composition of the Olfactory receptor neuron (captions in German)
  • olfactory epithelium pig
    olfactory epithelium pig

See also

References

  1. ^ Gizurarson, S. (2012). Anatomical and Histological Factors Affecting Intranasal Drug and Vaccine Delivery. Current Drug Delivery, 9(6), 566–582. doi:10.2174/156720112803529828 10.2174/156720112803529828
  2. S2CID 25263022{{citation}}: CS1 maint: numeric names: authors list (link
    )
  3. ^ Ross, MH, Histology: A Text and Atlas, 5th Edition. Philadelphia: Lippincott, Williams and Wilkins, 2006. page 615-616.
  4. ^ "Dendritic knob". yeast genome.org. Retrieved 28 July 2019.
  5. ^ a b Ross, MH, Histology: A Text and Atlas, 5th Edition. Philadelphia: Lippincott, Williams and Wilkins, 2006. page 616.
  6. PMID 26016700
    .
  7. ^ Purves, Dale; Augustine, George J.; Fitzpatrick, David; Katz, Lawrence C.; LaMantia, Anthony-Samuel; McNamara, James O.; Williams, S. Mark (2001-01-01). "The Olfactory Epithelium and Olfactory Receptor Neurons". {{cite journal}}: Cite journal requires |journal= (help)
  8. PMID 27560601
    .
  9. ^
    PMID 25662265. {{cite book}}: |journal= ignored (help
    )
  10. ^ .
  11. .
  12. ^
    PMID 25662264. {{cite book}}: |journal= ignored (help
    )
  13. ^ .
  14. .
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  16. ^ .
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  19. ^ Purves, Dale; Augustine, George J.; Fitzpatrick, David; Katz, Lawrence C.; LaMantia, Anthony-Samuel; McNamara, James O.; Williams, S. Mark (2001-01-01). "The Transduction of Olfactory Signals". {{cite journal}}: Cite journal requires |journal= (help)
  20. PMID 25688305
    .
  21. .

External links