What is the internal nasal anatomy and its clinical significance?

Internal Nasal Anatomy and Its Clinical Significance

The internal nasal anatomy is a complex structure with high inter-individual variability that directly impacts respiratory function, and understanding its components is crucial for diagnosing and treating nasal obstruction, which affects up to one-third of the population. 1

Key Anatomical Structures

Nasal Septum

• Divides the nasal cavity into right and left passages
• Composed of:
  • Cartilaginous component (septal cartilage)
  • Bony components (perpendicular plate of ethmoid, vomer)
• Clinical significance:
  • Septal deviation is a common anatomical variant that can cause nasal obstruction 2
  • The superior border of septal cartilage angles downward rather than forming a linear extension of the nasal bones 3

Lateral Nasal Wall

• Contains three main turbinates (conchae):

  1. Inferior turbinate: Largest turbinate, critical for nasal airflow regulation
  2. Middle turbinate: Important surgical landmark for sinus procedures
  3. Superior turbinate: Smallest, located posterosuperiorly

• Clinical variants include:

  • Concha bullosa (pneumatized middle turbinate)
  • Paradoxical middle turbinate (convexity facing laterally)
  • Inferior turbinate hypertrophy 4

Nasal Valve

• Internal nasal valve: Narrowest part of the nasal airway

  • Formed by the junction of the upper lateral cartilage and septum
  • Accounts for approximately 50% of total airway resistance
  • Stenosis or collapse is a major cause of nasal obstruction 1

• External nasal valve: Formed by the columella, nasal floor, and alar rim

Mucosal Lining and Physiology

• The nasal mucosa varies significantly throughout the nasal cavity:

  • Respiratory epithelium (pseudostratified ciliated columnar) in most areas
  • Olfactory epithelium in the superior region
  • Squamous epithelium at the nasal vestibule 5

• Functional aspects:

  • Mucociliary clearance: Critical for removing particles and pathogens
  • Humidification and warming of inspired air
  • Airflow sensing via specialized receptors
  • Autonomic regulation of nasal cycle 1

Clinical Significance

Nasal Obstruction

• Common causes based on anatomy:
  1. Septal deviation
  2. Inferior turbinate hypertrophy
  3. Internal nasal valve collapse/stenosis 1

Surgical Considerations

• Precise knowledge of anatomical variants is essential for:
  • Septoplasty
  • Turbinate reduction procedures
  • Functional rhinoplasty
  • Endoscopic sinus surgery 2

Soft Tissue Variations

• The soft tissue overlying the cartilaginous skeleton varies in thickness along the dorsum
• Subcutaneous fat distribution is highly individualized
• The nasalis muscle shows significant variation in presence and configuration 3
• These variations impact external nasal appearance and should be considered in rhinoplasty planning

Imaging Assessment

• CT imaging is valuable for evaluating:
  • Anatomical variants
  • Extent of pathology
  • Surgical planning
• 3D modeling can help predict post-surgical results 2

Common Pitfalls in Clinical Assessment

• Failure to recognize internal nasal valve dysfunction as a cause of obstruction
• Overlooking the contribution of mucosal inflammation to nasal obstruction
• Not considering the nasal cycle when evaluating nasal patency
• Focusing solely on septal deviation without assessing other anatomical factors 1

The understanding of nasal anatomy has evolved significantly with advanced imaging techniques, allowing for better appreciation of the high degree of inter-individual variability and its impact on nasal function and pathology 2.