What is the internal nasal anatomy and its clinical significance?

Internal Nasal Anatomy and Its Clinical Significance

Understanding the complex internal nasal anatomy is essential for diagnosing and treating nasal obstruction, which affects up to one-third of the population. 1

Basic Anatomical Structure

The internal nasal cavity consists of several key components:

Nasal Septum

• Divides the nasal cavity into right and left passages
• Composed of:
  • Cartilaginous portion anteriorly (septal cartilage)
  • Bony portion posteriorly (perpendicular plate of ethmoid and vomer)
• Clinical significance: Septal deviation is a common anatomic cause of nasal obstruction 2, 1
• The septal cartilage angles downward from the nasal bones rather than forming a linear extension 3

Lateral Nasal Wall

The lateral nasal wall contains three (sometimes four) turbinates:

1. Inferior Turbinate

   • Largest turbinate
   • Attached to the maxilla
   • Highly vascular with erectile tissue
   • Clinical significance: Hypertrophy is a common cause of nasal obstruction 2, 1

2. Middle Turbinate

   • Attached to the ethmoid bone
   • Clinical significance: Can develop anatomic variants such as:
     • Concha bullosa (pneumatization of the middle turbinate)
     • Paradoxical middle turbinate (convexity facing laterally) 2
   • Important surgical landmark for sinus procedures

3. Superior Turbinate

   • Smaller structure higher in the nasal cavity
   • Contains olfactory epithelium

4. Supreme Turbinate (when present)

   • Smallest and highest turbinate
   • Present in some individuals

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
  • Clinical significance: Valve stenosis or collapse is a major cause of nasal obstruction 1

Mucosal Lining and Physiology

• The nasal cavity is lined with respiratory epithelium (pseudostratified ciliated columnar epithelium)
• Contains:
  • Goblet cells producing mucus
  • Ciliated cells for mucociliary clearance
  • Submucosal glands
• The surface epithelium varies in:
  • Cell types present in different intranasal locations
  • Distribution between species
  • Abundance of secretory products 4

Clinical Significance

Nasal Obstruction

The most common anatomical causes of nasal obstruction include:

1. Internal nasal valve stenosis/collapse
2. Septal deviation
3. Turbinate hypertrophy 1

Surgical Considerations

• High inter-individual variability exists in nasal cavity structure 5
• Precise knowledge of anatomical variants is crucial for both radiologists and ENT surgeons 5
• The soft tissue structures (muscle, skin, fat) overlying the cartilaginous skeleton vary in thickness along the dorsum and are individualized 3
• The nasalis muscle was identifiable in 75% of specimens in one study, with variable patterns of traversing the nose 3

Diagnostic Imaging

• CT imaging is valuable for assessing nasal cavity variants
• 3D modeling can help predict post-surgical results 5
• Understanding the relationship between internal structures and external nasal profile is important for surgical planning 3

Common Anatomical Variants

1. Septal Deviation

   • Present in varying degrees in most individuals
   • May cause unilateral or bilateral obstruction

2. Turbinate Variations

   • Inferior turbinate hypertrophy
   • Concha bullosa (pneumatized middle turbinate)
   • Paradoxical middle turbinate

3. Soft Tissue Variations

   • Variable distribution of subcutaneous fat (continuous presence from root to tip in 50% of specimens) 3
   • Variable configuration of nasalis muscle 3

Understanding these anatomical structures and their variations is critical for accurate diagnosis and effective treatment of nasal conditions, particularly those causing obstruction.