External Nares (Nostrils)

1. Overview

The external nares, commonly known as the nostrils, are the paired external openings of the nose through which air enters the respiratory system. They are the anterior openings of the nasal cavities, serving as the first point of contact for inhaled air. These structures play a vital role in respiration, olfaction, humidification, and defense against airborne pathogens and particulates.

2. Location

The external nares are located at the inferior aspect of the nose, facing downward and slightly laterally. Anatomically, they lie:

• On either side of the nasal septum

• Inferior to the nasal bones and upper lateral cartilages

• Above the upper lip and flanked by the nasal alae (wings of the nose)

They form the entrance to the nasal vestibule, which continues posteriorly into the nasal cavity proper.

3. Structure

The external nares are made up of several anatomical components:

• Nasal cartilages:

  • Lower lateral (alar) cartilages form the nostril rims and help maintain shape and patency

  • Septal cartilage divides the two nares medially

• Nasal vestibule: Just inside each naris; lined by skin containing vibrissae (coarse nasal hairs) and sebaceous glands

• Epithelial lining: Stratified squamous epithelium in the vestibule, transitioning to pseudostratified columnar (respiratory) epithelium deeper in the nasal cavity

• Muscles: Muscles such as the nasalis and depressor septi nasi influence nostril size during facial expression and breathing

4. Function

The external nares serve several essential functions:

• Air entry: Primary entryway for inhaled air during normal breathing

• Filtration: Vibrissae trap large particles, dust, and insects

• Defense: Acts as a mechanical and immunological barrier via mucociliary activity and immune cells

• Voice resonance and olfaction: Contribute indirectly to vocal resonance and olfactory airflow direction

5. Physiological Role(s)

The external nares contribute significantly to respiratory and sensory physiology:

• Airflow regulation: Muscles can flare or constrict nostrils during forced respiration (e.g., during exercise or stress)

• Thermoregulation: Nasal passages warm or cool incoming air to near body temperature

• Humidification: Inspired air is humidified by the moist nasal mucosa before reaching the lungs

• Olfaction: Proper nasal airflow through the nares is essential for directing air to the olfactory epithelium in the superior nasal cavity

6. Clinical Significance

Nasal Obstruction

Blocked or narrowed nares due to septal deviation, nasal valve collapse, or congenital malformations can result in:

• Mouth breathing

• Snoring or sleep apnea

• Reduced olfaction and air filtration

Corrected via surgical interventions such as septoplasty or nasal valve repair.

Nasal Vestibulitis

Inflammation or infection of the nasal vestibule, often due to:

• Staphylococcus aureus colonization

• Nose picking or excessive blowing

Symptoms: Redness, crusting, pain, and possible pustule formation. Treated with topical or oral antibiotics.

Nasal Polyps

Though usually located deeper in the nasal cavity, large anterior polyps may protrude into or block the nares, impairing airflow. Treatment involves corticosteroids or polypectomy.

Foreign Body Aspiration

Especially in children, foreign bodies may become lodged in the external nares, leading to:

• Foul-smelling unilateral discharge

• Nasal obstruction

Requires careful removal under visualization to prevent mucosal damage or aspiration.

Cosmetic and Reconstructive Surgery

External nares are key landmarks in rhinoplasty. Symmetry, size, and shape influence both aesthetic appearance and functional airflow. Reconstruction may be needed after trauma or congenital anomalies such as cleft nose.