Airway Anatomy

Nose & Pharynx - Air's First Hurdles

• Nose:
  • Functions: Warms, humidifies, filters air.
  • Structures: Nasal septum; Turbinates (superior, middle, inferior) ↑ surface area for air conditioning.
  • Kiesselbach's plexus (Little's area): Anterior septum, common epistaxis site.
• Pharynx: Muscular tube (approx. 12-14 cm); common air/food passage.
  • Nasopharynx: Posterior to nose, extends to soft palate. Contains adenoids (pharyngeal tonsils), Eustachian tube openings.
  • Oropharynx: Soft palate to superior border of epiglottis. Contains palatine & lingual tonsils.
  • Laryngopharynx (Hypopharynx): Epiglottis to inferior border of cricoid cartilage (level of C6 vertebra).

  ⭐ Waldeyer's tonsillar ring: Protective lymphoid ring composed of pharyngeal, tubal, palatine, and lingual tonsils. Clinical significance: hypertrophy → potential airway obstruction; common site for infections (e.g., tonsillitis).

Larynx Anatomy - Guardian of the Gate

• Cartilages of the Larynx:

  Type	Cartilages	Key Feature
  Unpaired	Thyroid, Cricoid, Epiglottis	Thyroid: largest
  Paired	Arytenoid, Corniculate, Cuneiform	Arytenoid: vocal cord attachment

• Laryngeal Muscles & Actions:

  • Intrinsic: Fine vocal cord movements.
    • Abductor: Posterior Cricoarytenoid (PCA) - 📌 "PCA Pulls Cords Apart"
    • Adductors: Lateral Cricoarytenoid, Interarytenoids (Transverse & Oblique)
    • Tensor: Cricothyroid (CT)
    • Relaxer/Adductor: Thyroarytenoid (Vocalis muscle)
  • Extrinsic: Elevate/depress larynx during swallowing.

• Nerve Supply:

  • Sensory:
    • Above vocal cords (Supraglottis): Internal laryngeal nerve (branch of Superior Laryngeal Nerve - SLN).
    • Below vocal cords (Infraglottis): Recurrent Laryngeal Nerve (RLN).
  • Motor:
    • Cricothyroid muscle: External laryngeal nerve (branch of SLN).
    • All other intrinsic muscles: RLN.

⭐ All intrinsic laryngeal muscles are supplied by the recurrent laryngeal nerve (RLN) except the cricothyroid (supplied by the external branch of the superior laryngeal nerve).

• Laryngeal Nerve Supply Pathway:

Trachea & Bronchi - Pipes to Perfection

• Trachea (Windpipe):
  • Length: 10-12 cm; Diameter: ~2.5 cm.
  • 16-20 C-shaped hyaline cartilage rings; open posteriorly (trachealis muscle).
  • Lining: Ciliated pseudostratified columnar epithelium.
  • Bifurcation: Carina (level of sternal angle, T4-T5 vertebrae).
• Bronchial Tree:
  • Main (Primary) Bronchi:
    • Right: Wider, shorter (~2.5 cm), more vertical (angle ~25°).
    • Left: Narrower, longer (~5 cm), more horizontal (angle ~45°).
  • Lobar (Secondary) Bronchi: 3 on the right, 2 on the left.
  • Segmental (Tertiary) Bronchi: Supply bronchopulmonary segments.
  • Cartilage: Rings in trachea → Irregular plates in bronchi → Absent in bronchioles.

⭐ The right main bronchus is wider, shorter, and more vertical than the left, making it a common site for foreign body aspiration.

📌 Right main bronchus: Ready for Rubbish (foreign bodies).

Pediatric Airway - Tiny Tubes, Big Deals

Pediatric airways differ significantly, posing unique challenges. Key differences:

*   Prone to obstruction; rapid desaturation.
*   Large occiput: shoulder roll for neutral ("sniffing") position.
*   Larynx & epiglottis: straight blade (Miller) often preferred for infants.
*   ETT size (uncuffed): $(Age/4) + 4$. Cuffed: $(Age/4) + 3.5$.
*   📌 Mnemonic (Narrowest): **C**hildren **R**ing is **C**ricoid.

⭐ The narrowest part of the pediatric airway is the cricoid cartilage (functionally, a complete ring), unlike the glottis in adults.

High‑Yield Points - ⚡ Biggest Takeaways

• Narrowest adult airway: Rima glottidis; pediatric: Cricoid cartilage (complete ring, subglottic).
• Trachea: begins at C6 vertebra, bifurcates at T4-T5 (carina).
• Right main bronchus: wider, shorter, more vertical than left; common aspiration site.
• Sensory above vocal cords: Internal Superior Laryngeal Nerve; below cords & trachea: Recurrent Laryngeal Nerve.
• Motor to intrinsic laryngeal muscles: Recurrent Laryngeal Nerve (except cricothyroid by External SLN).
• Vallecula: depression anterior to epiglottis, key for Macintosh blade placement.