Meatuses (Superior, Middle, Inferior)

1. Overview

The nasal meatuses are curved, narrow air passages located within the lateral walls of the nasal cavity, beneath each corresponding nasal concha. There are three paired meatuses: the superior meatus, middle meatus, and inferior meatus. These channels play vital roles in airflow regulation, drainage of paranasal sinuses, and humidification of inhaled air. Each meatus serves as a drainage route for adjacent sinuses or ducts, integrating the upper respiratory and sinus systems.

2. Location

The nasal meatuses are located on the lateral walls of the nasal cavity, formed by the overhanging superior, middle, and inferior nasal conchae (also called turbinates). Their positions are as follows:

• Superior meatus: Beneath the superior nasal concha

• Middle meatus: Beneath the middle nasal concha

• Inferior meatus: Beneath the inferior nasal concha, and above the floor of the nasal cavity

3. Structure

Each meatus is a narrow groove or channel formed by the bony nasal conchae projecting medially from the lateral nasal wall. They are lined by:

• Pseudostratified ciliated columnar epithelium (respiratory epithelium)

• Mucus-secreting goblet cells for trapping debris

Each meatus has anatomical openings for various sinuses or ducts:

Superior Meatus

• Drains the posterior ethmoidal air cells

Middle Meatus

This is the most complex and clinically important meatus. It contains the osteomeatal complex, a key region for sinus drainage:

• Hiatus semilunaris: Crescent-shaped groove leading to the ethmoid infundibulum

• Ethmoid bulla: A bulge formed by middle ethmoidal air cells

• Drainage:

  • Anterior ethmoidal air cells

  • Frontal sinus (via frontonasal duct)

  • Maxillary sinus

Inferior Meatus

• Receives the opening of the nasolacrimal duct, which drains tears from the eyes

4. Function

The nasal meatuses facilitate several critical functions:

• Airflow regulation: Direct and distribute inspired air within the nasal cavity

• Drainage channels: Serve as exit points for mucus produced in the paranasal sinuses and lacrimal apparatus

• Air conditioning: Help warm, moisten, and filter incoming air through mucosal contact

5. Physiological Role(s)

The meatuses contribute significantly to upper respiratory physiology:

• Mucociliary clearance: Cilia within the mucosa move mucus and trapped particles toward the nasopharynx for clearance

• Protection: Aid in filtering pathogens and pollutants before they enter the lower respiratory tract

• Thermoregulation: Maximize surface area contact to warm and humidify air

• Olfaction support: Air directed through the superior meatus can reach the olfactory epithelium in the upper nasal cavity

6. Clinical Significance

Sinusitis

Blockage of the middle meatus—specifically the osteomeatal complex—is a major contributor to chronic rhinosinusitis. Inflammation or anatomical variations can obstruct drainage from the maxillary, frontal, and anterior ethmoid sinuses, causing fluid retention and infection.

Nasolacrimal Duct Obstruction

In the inferior meatus, blockage of the nasolacrimal duct can lead to:

• Excessive tearing (epiphora)

• Recurrent eye infections (dacryocystitis)

Often seen in infants or due to trauma or chronic inflammation.

Endoscopic Sinus Surgery

The meatuses, especially the middle meatus, are critical access points in functional endoscopic sinus surgery (FESS) to restore drainage and ventilation to blocked sinuses.

Anatomic Variations

• Concha bullosa: Air-filled middle turbinate that may narrow the middle meatus and predispose to sinus disease

• Haller cells: Ethmoidal air cells near the orbit that may obstruct the maxillary ostium

Epistaxis (Nosebleeds)

Though more common in the anterior septum (Kiesselbach’s plexus), inflammation or trauma in the meatuses may also contribute to recurrent nosebleeds, particularly in dry environments or with chronic rhinitis.