Anatomy of Nasal Sinuses
The nasal sinuses are air-filled cavities lined with pseudostratified ciliated columnar epithelium that develop at different ages during childhood, with the maxillary sinus developing first (between birth and 12 months) followed by the ethmoid, frontal, and sphenoid sinuses. 1
Paranasal Sinus Development
- Maxillary sinus: First to develop, begins significant pneumatization between birth and 12 months; reaches the level of the nasal floor by approximately 12 years of age 1
- Ethmoid sinuses: Present as rudimentary structures at birth; reach adult size by 12-14 years of age 1
- Frontal and sphenoid sinuses: Develop later than the maxillary and ethmoid sinuses 1
Anatomical Structure and Location
Maxillary Sinuses
- Paired sinuses located in the maxillary bones
- Drain through the ostiomeatal complex into the middle meatus 1
- Intimately related to the roots of posterior maxillary teeth, explaining dental pain during sinusitis 2
- Floor often reaches the level of the nasal floor in adults
Ethmoid Sinuses
- Complex honeycomb-like structure of multiple air cells
- Divided into anterior and posterior ethmoid cells
- Anterior ethmoid cells drain into the middle meatus via the ostiomeatal complex 1
- Posterior ethmoid cells drain into the superior meatus
- Positioned centrally within the nasal complex, explaining why ethmoid disease often spreads to other sinuses 3
Frontal Sinuses
- Located in the frontal bone above the orbits
- Drain through the frontal recess into the middle meatus via the ostiomeatal complex 1
- Due to their location, infections here have greater propensity to cause intracranial complications 1
Sphenoid Sinuses
- Located in the body of the sphenoid bone
- Drain into the sphenoethmoidal recess
- Critical anatomical relationships: adjacent to the optic nerve, cavernous sinus, and carotid artery 1
- Infections or tumors can affect these vital structures 1
The Ostiomeatal Complex
- Critical anatomical region where the maxillary, anterior ethmoid, and frontal sinuses drain 1
- Located in the middle meatus of the nasal cavity
- Consists of:
- Middle turbinate
- Uncinate process
- Ethmoid infundibulum
- Hiatus semilunaris
- Maxillary sinus ostium 1
- Most frequently involved region in sinusitis due to its location and exposure to environmental factors 1
- Obstruction of this complex can predispose to the development of sinusitis affecting multiple sinuses 1
Sinus Physiology
- Sinuses are lined with pseudostratified ciliated columnar epithelium interspersed with goblet cells 1
- Cilia sweep mucus toward the ostial openings in a specific pattern (mucociliary clearance) 1
- Blood flow in the maxillary sinus is approximately 100 mL/100 g tissue per minute (similar to nasal blood flow) 1
- Obstruction of sinus ostia can lead to:
Clinical Significance of Anatomical Variations
Anatomical variations that may predispose to sinusitis:
Variations with potential impact on surgical safety:
- Anterior clinoid process pneumatization (18%)
- Infraorbital ethmoid cells (12%)
- Sphenomaxillary plate (11%)
- Supraorbital recess (6%) 4
Relationship to Dental Structures
- The maxillary sinus floor is intimately related to the roots of maxillary teeth, particularly premolars and molars 2, 5
- Sinusitis can cause dental pain due to pressure changes in the sinus cavity affecting adjacent dental roots 2
- Sinusitis-related dental pain typically affects multiple teeth and may worsen with position changes, unlike primary dental pain which is usually localized to a specific tooth 2
Understanding the complex anatomy of the nasal sinuses is essential for diagnosing and treating sinus pathologies, as well as for safe surgical intervention. The central position of the ethmoid sinus and the critical role of the ostiomeatal complex in sinus drainage highlight why obstruction in these areas often leads to widespread sinus disease.