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Ostiomeatal complex: want to learn more about it?

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Ostiomeatal complex

The ostiomeatal complex (OMC) is the collection of structures that aids in mucus drainage and airflow between the maxillary sinus, the anterior ethmoid air cells, and the frontal sinus. This article will evaluate the boundaries, composition and anatomical variations of the ostiomeatal complex.

Relation of the OMC with the paranasal sinuses

The paranasal sinuses assist with several mechanical and physiological functions. These include:

  • humidifying the inspired air.
  • Lightening the skull.
  • Regulating intranasal pressure.
  • Enhancing olfaction.
  • Adding resonance to the voice.

Additionally, it has been postulated that the sinuses produce mucus that is free of environmental contaminants. This mucus is then secreted into the superior and middle meatus in order to mitigate the contamination present in the mucus that is in contact with the air and its contaminants.

These functions would be compromised in instances where the paranasal sinuses are filled with fluid and are unable to be drained. The anterior paranasal sinuses (anterior ethmoid air cells, maxillary, and frontal) drain their contents by way of the ostiomeatal complex (unit). This cluster of ostia and their corresponding drainage channels are located on the lateral wall of the nasal cavity, deep to the middle concha. Contents of the anterior paranasal sinuses that enter the ostiomeatal complex will subsequently drain into the middle meatus before traveling into the nasopharynx.

Frontal and maxillary sinuses (medial view)


When the middle concha is reflected superiorly, the borders and components can be more readily appreciated.

  • Anteriorly, the unit is in open communication with the anterior nasal cavity. The agger nasi and atrium of the middle meatus also have an anterosuperior, and anterior (respectively) relations to the complex.
  • Superiorly, the ostiomeatal complex (OMC) is limited by the basal lamella. The basal lamella is a thin piece of lamina papyracea that attaches the middle turbinate (concha) to the lateral wall of the nasal cavity.
  • Posteriorly, The basal lamella continues along the length of the middle turbinate and consequently forms the posterior border of the space.
  • Inferiorly, the ostiomeatal unit has an open communication with the middle meatus. The drained contents of the unit will travel in the meatus along with the superior border of the inferior concha, which forms the floor of the middle meatus.
  • Medially, the complex is limited by the body of the middle concha. Laterally, the lamina papyracea of the ethmoid sinuses borders the complex.

Lateral wall of the nasal cavity (overview)


The most striking feature of the ostiomeatal complex is the laterally protruding structure spanning the middle third of the middle concha, called the bulla ethmoidalis (ethmoid bulla). The convexed bulge is created by the presence of the middle ethmoidal air cells and as a result, it contains an ostium that drains this space.

Ethmoidal bulla (posterior view)

Located anteroinferiorly to the ethmoid bulla, and posterior to the uncinate process is a curved furrow called the hiatus semilunaris. It contains the maxillary ostium and an accessory maxillary ostium towards the inferior aspect of the groove and the ostia of the anterior ethmoidal air cells anteriorly.

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This groove is continuous with the ethmoidal infundibulum, which courses superiorly and deep to the anterior aspect of the middle concha and lateral to the orbital plate of the ethmoid bone. The frontal sinus is, therefore, able to communicate with and drain its contents into the ostiomeatal complex because of the connection between its frontonasal duct (recess) and the ethmoidal infundibulum.

Ethmoidal infundibulum (posterior view)

The uncinate process, which forms the anterior and medial limitation of the hiatus semilunaris and the ethmoidal infundibulum (respectively), is a thin, crescent-shaped, bony leaflet that emerges from the ethmoidal labyrinth posteroinferiorly.

Uncinate process of the ethmoidal bone (posterior view)

Anatomical variations

Several types of anatomical variations, of either pre-developmental or post-developmental aetiologies, have been observed in the ostiomeatal complex. The structures most frequently affected include the uncinate process, nasal septum, and middle turbinate.

Concha bullosa

The middle turbinate may be congenitally filled with air (pneumatized). Clinicians refer to this variation as a concha bullosa. Also, there are instances where the middle turbinate develops in a sigmoid shape – with a superior convexity and an inferior concavity. This condition is referred to as a paradoxical middle turbinate.

Uncinate process deviation

The uncinate process may deviate from its typical posteroinferior course and arise in a medial fashion that obstructs the middle meatus and the ethmoid infundibulum. In cases where hypoplastic maxillary sinuses are present, lateral elevation of the uncinate process until it fuses with the medial orbital wall can impede the integrity of the orbit.

Septal deviation

Congenital or traumatic deviation of the nasal septum can result in compression of the middle meatus and subsequent obstruction of the drainage pathway. Complications of these variations arise when they obstruct the drainage pathway of the respective paranasal sinuses. Pneumatization of respective areas has been associated with reduced ventilation to the sinuses. As a result, stasis of the mucous within the sinus can result in sinopathies such as sinusitis and rhinosinusitis.

Ostiomeatal complex: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

What do you prefer to learn with?

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references


  • Netter, F. (2014). Atlas of Human Anatomy. 6th ed. Philadelphia, PA: Saunders/Elsevier, p.36.
  • Riello, A. and Boasquevisque, E. (2008). Anatomical variants of the ostiomeatal complex: tomographic findings in 200 patients. Radiologia Brasileira, 41(3), pp.149--154.
  • Sinnatamby, C. and Last, R. (2011). Last's Anatomy. 12th ed. Edinburgh: Churchill Livingstone/Elsevier, p.374.
  • Snow, J., Ballenger, J. and Snow, J. (2003). Ballenger's Otorhinolaryngology. 16th ed. Hamilton, Ont.: BC Decker, pp.553, 674.


  • Frontal and maxillary sinuses (medial view) - Yousun Koh 
  • Lateral wall of the nasal cavity (overview) - Yousun Koh  
  • Ethmoidal bulla (posterior view) - Samantha Zimmermann
  • Ethmoidal infundibulum (posterior view) - Samantha Zimmermann
  • Uncinate process of the ethmoidal bone (posterior view) - Samantha Zimmermann
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