Nasal concha

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Turbinate
)
Nasal concha/turbinate
Lateral wall of nasal cavity, showing ethmoid bone in position. (Superior and middle in pink, and inferior in blue.)
Details
Identifiers
Latinconchae nasales
MeSHD014420
FMA57456
Anatomical terms of bone
Illustration of upper respiratory system

In

bone that protrudes into the breathing passage of the nose in humans and various animals. The conchae are shaped like an elongated seashell, which gave them their name (Latin concha from Greek κόγχη). A concha is any of the scrolled spongy bones of the nasal passages in vertebrates.[3]

In humans, the conchae divide the nasal airway into four groove-like air passages, and are responsible for forcing inhaled air to flow in a steady, regular pattern around the largest possible surface area of nasal mucosa. As a ciliated mucous membrane with shallow blood supply, the nasal mucosa cleans and warms the inhaled air in preparation for the lungs.

A rapidly dilating arteriolar circulation to these bones may lead to a sharp increase in the pressure within, in response to acute cooling of the body core. The pain from this pressure is often referred to as "

brain freeze", and is frequently associated with the rapid consumption of ice cream. The shallowness of the venous blood supply of the mucosa contributes to the ease with which nosebleed
can occur.

Structure

Conchae are composed of

medially and downward into the nasal airway. Each pair is composed of one concha in either side of the nasal cavity, divided by the septum.[4]

The superior conchae are smaller structures, connected to the middle conchae by nerve-endings, and serve to protect the olfactory bulb. The superior conchae attach to the ethmoid bone. The openings to the posterior ethmoidal sinuses exist under the superior meatus.[3] The sphenoid sinus ostium exists medial to the superior turbinate.[5]

The

middle meatus.[3] In humans, they are usually as long as the little finger
.

The inferior conchae are the largest turbinates, can be as long as the index finger in humans, and are responsible for the majority of airflow direction, humidification, heating, and filtering of air inhaled through the nose.[3]

The inferior conchae are graded 1–4 based on the inferior concha classification system (known as the inferior turbinate classification system) in which the total amount of the airway space that the inferior concha takes up is estimated. Grade 1 is 0–25% of the airway, grade 2 is 26–50% of the airway, grade 3 is 51–75% of the airway and grade 4 is 76–100% of the airway.[7]

There is sometimes a pair of supreme conchae superior to the superior conchae. When present, these usually take the form of a small crest.

Function

The conchae comprise most of the

fifth cranial nerve), allowing for tremendous erectile capabilities of nasal congestion and decongestion, in response to the weather conditions and changing needs of the body.[4] In addition, the erectile tissue undergoes an often unnoticed cycle of partial congestion and decongestion called the nasal cycle. The flow of blood to the nasal mucosa in particular the venous plexus of the conchae is regulated by the pterygopalatine ganglion
and heats or cools the air in the nose.

The nasopulmonary and nasothoracic

intercostal muscles, and the diaphragm
.

The conchae are also responsible for

filtration, heating, and humidification of air inhaled through the nose. Of these three, filtration is achieved mostly by other more effective means such as mucous and cilia. As air passes over the conchae, it is heated to 32–34 °C (89–93 °F), humidified (up to 98% water saturation) and filtered.[4]

Immunological role

The

micrometers. The respiratory epithelium also serves as a means of access for the lymphatic system, which protects the body from being infected by viruses or bacteria.[3]

Smell

The conchae provide, first and foremost, the humidity needed to preserve the delicate olfactory epithelium, which in turn is needed to keep the olfactory receptors healthy and alert. If the epithelial layer gets dry or irritated, it may cease to function. This is usually a temporary condition but, over time, may lead to chronic anosmia.[4] The turbinates also increase the surface area of the inside of the nose, and, by directing and deflecting airflow across the maximum mucosal surface of the inner nose, they are able to propel the inspired air. This, coupled with the humidity and filtration provided by the conchae, helps to carry more scent molecules towards the higher, and very narrow regions of the nasal airways, where olfaction nerve receptors are located.[3]

The superior conchae completely cover and protect the nerve axons piercing through the

cranial nerve).[4]
Research has shown that there is a strong connection between these nerve endings and activation of the olfactory receptors, but science has yet to fully explain this interaction.

Clinical significance

Dysfunction

Large, swollen conchae, often referred to clinically as turbinates, may lead to blockage of nasal breathing.

Allergies, exposure to environmental irritants, or a persistent inflammation within the sinuses can lead to turbinate swelling. Deformity of the nasal septum can also result in enlarged turbinates.[8]

Treatment of the underlying allergy or irritant may reduce turbinate swelling. In cases that do not resolve, or for treatment of

deviated septum
, turbinate surgery may be required.

Surgery

Main article: Turbinectomy

inferior turbinates
).

In the case of

turbinate reduction surgery. Risks of reduction of the inferior or middle turbinates include empty nose syndrome.[8] Dr. Houser: "this is especially true in cases of anterior inferior turbinate (IT) resection because of its important role in the internal nasal valve."[9]

sinus ostia and can result in recurrent sinusitis. In some cases, the concha bullosa
may be resected to help resolve persistent symptoms.

Other animals

nares
(nostrils) which expand during exercise. The nasal passages have two turbinates on either side which increase the surface area to which air is exposed.
1 : Concha nasalis dorsalis  
2 : Concha nasalis media    
3 : Concha nasalis ventralis

Generally, in animals, nasal conchae are convoluted structures of thin bone or cartilage located in the

respiratory
turbinates are found in most mammals and birds.

Animals with respiratory turbinates can breathe faster without drying out their lungs, and consequently can have a faster metabolism.

gray wolf ancestors) to survive in the harsh Arctic environment and other cold areas of northern Eurasia and North America, which are both very dry and very cold.[13]

cartilaginous. The possibility has also been raised that these ridges are associated with an olfactory epithelium rather than turbinates.[16] Nonetheless, the possible presence of maxilloturbinates suggests that Glanosuchus may have been able to rapidly breathe without drying out the nasal passage, and therefore could have been an endotherm.[10][14][16]

The bones of nasal turbinates are very fragile and seldom survive as fossils. In particular none have been found in fossil birds.

cynodonts, such as Thrinaxodon and Diademodon. This suggests that they may have had fairly high metabolic rates.[18][19][20][21] The paleontologist John Ruben and others have argued that no evidence of nasal turbinates has been found in dinosaurs. All the dinosaurs they examined had nasal passages that they claimed were too narrow and too short to accommodate nasal turbinates, so dinosaurs could not have sustained the breathing rate required for a mammal-like or bird-like metabolic rate while at rest, because their lungs would have dried out.[15][22][23] However, objections have been raised against this argument. Nasal turbinates are absent or very small in some birds, such as ratites, Procellariiformes and Falconiformes. They are also absent or very small in some mammals, such as anteaters, bats, elephants, whales and most primates, although these animals are fully endothermic and in some cases very active.[24][25][26][27] Furthermore, ossified turbinate bones have been identified in the ankylosaurid dinosaur Saichania.[28]

See also

This article uses anatomical terminology.

Additional images

  • Nasal conchae: Blocked/free
    Nasal conchae: Blocked/free
  • Normal Nose CT Front cross section
    Normal Nose CT Front cross section
  • Coronal section of nasal cavities
    Coronal section of nasal cavities
  • Right nasal airway passage
    Right nasal airway passage
  • Nasal conchae
    Nasal conchae
  • Nasal concha
    Nasal concha

Notes

  1. ISBN 978-0-12-811837-5
    . In man, the three conchae define the meatuses: Inferior meatus: between inferior concha/turbinate and floor of nasal cavity; Middle meatus: between middle concha/turbinate and inferior concha; Superior meatus: between superior concha/turbinate and middle concha.
  2. S2CID 79294211
    .
  3. ^ a b c d e f Anatomy of the Human Body Archived 2013-01-21 at the Wayback Machine Gray, Henry (1918) The Nasal Cavity.
  4. ^ a b c d e f Turbinate Dysfunction: Focus on the role of the inferior turbinates in nasal airway obstruction. Archived 2006-06-22 at the Wayback Machine S.S. Reddy, et al. Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
  5. S2CID 20061049
    .
  6. S2CID 5720770
    .
  7. S2CID 34156218
    .
  8. ^ a b Reduction/Removal of the Inferior Turbinate From the Sinus Info Center.
  9. ^ Houser SM. Surgical Treatment for Empty Nose Syndrome. Archives of Otolaryngology Head & Neck Surgery\ Vol 133 (No.9) Sep' 2007: 858–863.
  10. ^ a b Zimmer, C. (1994). "The Importance of Noses". Discover. 15 (8).
  11. S2CID 39880287
    .
  12. ^ a b c Wang (2008) p. 88.
  13. ^ a b Wang (2008) p. 87.
  14. ^
    PMID 28568303
    .
  15. ^
    doi:10.1093/icb/40.4.585
    .
  16. ^
    doi:10.1111/j.1096-3642.2006.00226.x
    .
  17. S2CID 7328047
    .
  18. ^ Brink, A.S. (1955). "A study on the skeleton of Diademodon". Palaeontologia Africana. 3: 3–39.
  19. ISBN 978-0-12-404120-2
    .
  20. S2CID 89393753
    .
  21. PMID 7778882
    .
  22. doi:10.1126/science.278.5341.1267.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  23. S2CID 84693210.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  24. PMID 5965973
    .
  25. PMID 5133493
    .
  26. S2CID 32082759
    .
  27. S2CID 38947951.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  28. ^ Maryańska, T. (1977). "Ankylosauridae (Dinosauria) from Mongolia". Palaeontologia Polonica. 37: 85–151.

References

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