View source for Paranasal sinuses

{{Short description|Air-filled spaces surrounding the nasal cavity}}
{{Redirect2|Sinuses|Sinus cavity|other sinuses|Sinus (disambiguation){{!}}Sinus}}
{{Infobox anatomy
| Name        = Paranasal sinuses
| Latin       = sinus paranasales
| Image       = Paranasal Sinuses ant.jpg
| Caption     = Paranasal sinuses seen in a frontal view
| Width       = 300
| Image2      = Paranasal Sinuses lat.jpg
| Caption2    = Lateral projection of the paranasal sinuses
| Precursor   = 
| System      = 
| Artery      = 
| Vein        = 
| Nerve       = 
| Lymph       = 
}}
'''Paranasal sinuses''' are a group of four paired [[skeletal pneumaticity|air-filled spaces]] that surround the [[nasal cavity]].<ref name="emed">{{cite web|title=Paranasal sinuses|date=23 December 2021 |url=http://emedicine.medscape.com/article/1899145-overview}}</ref> The [[maxillary sinus]]es are located under the [[eye]]s; the [[frontal sinus]]es are above the eyes; the [[Ethmoid sinus|ethmoidal sinuses]] are between the eyes, and the [[sphenoidal sinus]]es are behind the eyes. The [[sinus (anatomy)|sinuses]] are named for the [[Facial skeleton|facial bones and sphenoid bone]] in which they are located. The role of the sinuses is still debated.

==Structure==
Humans possess four pairs of paranasal sinuses, divided into subgroups that are named according to the [[bone]]s within which the sinuses lie. They are all innervated by branches of the [[trigeminal nerve]] (CN V).
* The [[maxillary sinus]]es, the largest of the paranasal sinuses, are under the [[Human eye|eye]]s, in the [[maxillary bones]] (open in the back of the [[semilunar hiatus]] of the nose). They are innervated by the [[maxillary nerve]] (CN V2).<ref name=":0">{{Cite web|date=2016-08-24|title=Paranasal Sinus Anatomy: Overview, Gross Anatomy, Microscopic Anatomy|url=http://emedicine.medscape.com/article/1899145-overview}}</ref>
* The [[frontal sinus]]es, superior to the eyes, in the [[frontal bone]], which forms the hard part of the [[forehead]]. They are innervated by the [[ophthalmic nerve]] (CN V1).<ref name=":0" />
* The [[ethmoid sinus|ethmoidal sinus]]es, which are formed from several discrete air cells within the [[ethmoid bone]] between the [[human nose|nose]] and the eyes. They are innervated by the [[ethmoidal nerves]], which branch from the [[nasociliary nerve]] of the ophthalmic nerve (CN V1).
* The [[sphenoidal sinus]]es, in the [[sphenoid bone]]. They are innervated by the ophthalmic and maxillary nerve (CN V1 and V2).<ref name=":0" />

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

==Functions==
{{Needs expansion|date=April 2024}}
One known function of the paranasal sinuses is the production of [[nitric oxide]], which also functions as a facilitator of oxygen uptake.<ref name="pubmed">{{cite journal|title=Nitric oxide and the paranasal sinuses|first1=Jon O|last1=Lundberg|journal=The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology|date=November 2008|volume=291|issue=11|pages=1479–1484|doi=10.1002/ar.20782|pmid=18951492|doi-access=free}}</ref>

== Development ==
Paranasal sinuses form developmentally through excavation of bone by air-filled sacs ([[skeletal pneumaticity|pneumatic diverticula]]) from the [[nasal cavity]]. This process begins prenatally (intrauterine), and it continues through the course of an organism's lifetime.{{cn|date=October 2025}}

The results of experimental studies suggest that the natural ventilation rate of a sinus with a single [[sinus ostium]] (opening) is extremely slow. Such limited ventilation may be protective for the sinus, as it would help prevent drying of its mucosal surface and maintain a near-sterile environment with high [[carbon dioxide]] concentrations and minimal [[pathogen]] access. Thus composition of gas content in the maxillary sinus is similar to [[venous blood]], with high carbon dioxide and lower [[oxygen]] levels compared to breathing air.<ref name="physiology">{{cite journal|first1=C. M. |last1=Hood |first2=R. C. |last2=Schroter |first3=D. J. |last3=Doorly |first4=E. J. S. M. |last4=Blenke |first5=N. S. |last5=Tolley |url=http://jap.physiology.org/content/107/4/1195.long|title=Computational modeling of flow and gas exchange in models of the human maxillary sinus|journal=Journal of Applied Physiology|date=1 October 2009 |volume=107 |issue=4 |pages=1195–1203 |doi=10.1152/japplphysiol.91615.2008 |pmid=19608923 |access-date=2017-09-07|archive-date=2017-09-04|archive-url=https://web.archive.org/web/20170904021832/http://jap.physiology.org/content/107/4/1195.long|url-status=dead|url-access=subscription }}</ref>

At birth, only the [[maxillary sinus]] and the [[ethmoid sinus]] are developed but not yet pneumatized; only by the age of seven are they fully aerated. The [[sphenoid sinus]] appears at the age of three, and the [[frontal sinus]]es first appear at the age of six, and fully develop during adulthood.<ref>{{cite journal |last1=Towbin |first1=Richard |last2=Dunbar |first2=J. Scott |date=1982 |title=The paranasal sinuses in childhood |journal=RadioGraphics |volume=2 |issue=2 |pages=253–279 |doi=10.1148/radiographics.2.2.253 |doi-access=free }}</ref>

===CT scans, radiographs (X-rays) and other illustrations===
<gallery>
File:CT Paranasal Sinuses Coronal MPR Soft Tissue Window.ogg|[[Coronal_plane|Coronal]] [[Computed tomography|CT]] scan of the paranasal sinuses (soft tissue)
File:CT Paranasal Sinuses Coronal MPR Bone Window.ogg|Coronal CT scan of the paranasal sinuses (bone)
File:Paranasal sinuses radiograph occipitofrontal.jpg|Paranasal sinuses radiograph (occipitofrontal)	
File:Paranasal sinuses radiograph occipitomental.jpg|Paranasal sinuses radiograph (occipitomental)	
File:Paranasal sinuses radiograph lateral.jpg|Paranasal sinuses radiograph (lateral)
File:3DPX-002305 Upper respiratory cast 3DFile Nevit Dilmen.stl|3D cast of maxillary, frontal, ethmoid and sphenoid sinuses, nasal cavity and hypopharynx
</gallery>

==Clinical significance==
===Inflammation===
{{Main|Sinusitis}}
The paranasal sinuses are joined to the [[nasal cavity]] via small orifices called [[Sinus ostium|ostia]]. These become blocked easily by allergic inflammation, or by swelling in the nasal lining that occurs with a [[common cold|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.<ref>Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, p. 68</ref>

These conditions may be treated with drugs such as [[decongestant]]s, which cause [[vasoconstriction]] in the sinuses; reducing inflammation; by traditional techniques of [[nasal irrigation]]; or by [[corticosteroid]].{{Medical citation needed|date=September 2023}}

===Cancer===
Malignancies of the paranasal sinuses comprise approximately 0.2%<ref>{{Cite journal |first1=Dario |last1=Consonni |first2=Simona |last2=Stella |first3=Nerina |last3=Denaro |first4=Alessandra |last4=Binazzi |first5=Barbara |last5=Dallari |first6=Sabrina |last6=Rugarli |first7=Flavia |last7=Borello |first8=Enzo |last8=Coviello |first9=Carolina |last9=Mensi |date=January 2024 |title=Survival of Patients with Sinonasal Cancers in a Population-Based Registry, Lombardy, Italy, 2008–2023 |journal=Cancers |language=en |volume=16 |issue=5 |page=896 |doi=10.3390/cancers16050896 |pmid=38473258 |pmc=10930825 |doi-access=free |issn=2072-6694 }}</ref> 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. [[Carcinoma]]s are more frequent than [[sarcoma]]s. Metastases are rare. [[Neoplasm|Tumours]] of the sphenoid and frontal sinuses are extremely rare.

==Etymology==
''Sinus'' is a [[Latin]] word meaning a fold, curve, or bay. Compare ''[[sine]]''.

==Animals==
Paranasal sinuses occur in many animals, including most [[mammal]]s, [[bird]]s, and [[crocodilia]]ns. They have also been discovered in non-avian [[dinosaur]]s. The bones occupied by sinuses vary with species.

==Illustrations==
<gallery>
File:Paranasal sinuses numbers.svg|Paranasal sinuses
File:Blausen 0800 Sinusitis.png|Illustration depicting sinusitis
</gallery>

==See also==
{{Anatomy terms}}

==References==
{{Reflist}}

==External links==

{{Nose anatomy}}

{{Authority control}}

[[Category:Human head and neck]]
[[Category:Bones of the head and neck]]
[[Category:Rhinology]]
[[Category:Otorhinolaryngology]]