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Paranasal sinuses

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Paranasal sinuses

Paranasal sinuses
Paranasal sinuses seen in a frontal view
Lateral projection of the paranasal sinuses
Details
Latin sinus paranasales
Identifiers
Gray's p.998
MeSH Paranasal+Sinuses
Dorlands
/Elsevier
Paranasal sinuses
TA [1]
FMA FMA:76587
Anatomical terminology

Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity (maxillary sinuses), above the eyes (frontal sinuses), between the eyes (ethmoidal sinuses), and behind the ethmoids (sphenoidal sinuses). The sinuses are named for the facial bones in which they are located.

Structure

Humans possess four paired paranasal sinuses, divided into subgroups that are named according to the bones within which the sinuses lie:

The paranasal air sinuses are lined with respiratory epithelium (ciliated pseudostratified columnar epithelium).

Development

Paranasal sinuses form developmentally through excavation of bone by air-filled sacs (pneumatic diverticula) from the venous blood, with high CO2 and lower O2 level compared to breathing air.[1]

Function

Lateral projection of the paranasal sinuses as seen in an X-ray image

The biological role of the sinuses is debated, but a number of possible functions have been proposed:

  • Decreasing the relative weight of the front of the skull, and especially the bones of the face.
  • Increasing resonance of the voice.
  • Providing a buffer against blows to the face.
  • Insulating sensitive structures like dental roots and eyes from rapid temperature fluctuations in the nasal cavity.
  • Humidifying and heating of inhaled air because of slow air turnover in this region.
  • Regulation of intranasal and serum gas pressures
  • Immunological defense

Despite these various proposals, the paranasal sinuses may not serve any biological function at all, instead developing as spandrels during ontogeny.[2]

Clinical relevance

Inflammation

The paranasal sinuses are joined to the nasal cavity via small orifices called ostia. These become blocked easily by allergic inflammation, or by swelling in the nasal lining that occurs with a cold. If this happens, normal drainage of mucus within the sinuses is disrupted, and sinusitis may occur. Because the maxillary posterior teeth are close to the maxillary sinus, this can also cause clinical problems if any disease processes are present, such as an infection in any of these teeth. These clinical problems can include secondary sinusitis, the inflammation of the sinuses from another source such as an infection of the adjacent teeth.[3]

These conditions may be treated with drugs such as decongestants, which cause vasoconstriction in the sinuses; reducing inflammation; by traditional techniques of nasal irrigation; or by corticosteroid.

Cancer

Malignancies of the paranasal sinuses comprise approximately 0.2% of all malignancies. About 80% of these malignancies arise in the maxillary sinus. Men are much more often affected than women. They most often occur in the age group between 40 and 70 years. Carcinomas are more frequent than sarcomas. Metastases are rare. Tumours of the sphenoid and frontal sinuses are extremely rare.

History

Etymology

Sinus is a latin word meaning a fold or pocket; in particular the front pocket in a toga.

Other animals

Paranasal sinuses occur in many other animals, including most mammals, birds, non-avian dinosaurs, and crocodilians. The bones occupied by sinuses are quite variable in these other species.

Additional images

See also

This article uses anatomical terminology; for an overview, see anatomical terminology.

References

  1. ^ http://jap.physiology.org/content/107/4/1195.long##
  2. ^ Zollikofer, Christopher; Weissman, John (24 October 2008). "A Morphogenetic Model of Cranial Pneumatization Based on the Invasive Tissue Hypothesis". The Anatomical Record 291 (11): 1446–1454.  
  3. ^ Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, p. 68

External links

  • Paranasal+sinuses at eMedicine Dictionary
  • The Anatomy Wiz: CT Paranasal Sinuses
  • Sinus Problems FAQ
  • Sinusitis: Symptoms, Causes, and Treatment
  • University of Texas Medical Branch: Paranasal Sinus Anatomy and Function   [Inactive link, November 2014]
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