Vocal Fold Structure and Function

Vocal Fold Structure and Function

Vocal Fold Structure and Function

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Vocal Fold Anatomy - Anatomy Unlayered

  • Paired mucosal folds within the larynx, crucial for phonation (voice production).
  • Extend from thyroid cartilage (anteriorly) to arytenoid cartilages (posteriorly).
  • Length: Adult males 17-23 mm; adult females 12-17 mm.
  • Layers (Hirano's Body-Cover Theory): 5 distinct histological layers, grouped into 3 functional sections.
    • Cover (Vibratory segment):
      • Epithelium: Stratified squamous, non-keratinized.
      • Superficial Lamina Propria (SLP) / Reinke's Space: Gelatinous, highly pliable. 📌 Site of Reinke's Edema.
    • Transition (Vocal Ligament - provides resilience):
      • Intermediate Lamina Propria (ILP): Elastic fibers.
      • Deep Lamina Propria (DLP): Collagenous fibers.
    • Body (Muscular core - provides bulk & tension):
      • Thyroarytenoid (Vocalis) Muscle.
  • Glottis: Airway space between the true vocal folds. Vocal fold tissue layers

⭐ Reinke's Space (SLP) is the primary vibrating layer; its condition critically impacts voice quality. Fluid accumulation (edema) here is common.

Phonation Physiology - Voice Mechanics

  • Myoelastic-Aerodynamic Theory: Voice production via interplay of muscle (myoelastic) & airflow (aerodynamic) forces.
    • Vocal folds (VFs) adduct (LCA, IA muscles).
    • Subglottic pressure ($P_{sub}$) builds.
    • $P_{sub}$ overcomes glottic resistance → VFs open (inferiorly then superiorly).
    • Air puff released, $P_{sub}$ drops.
  • Bernoulli Principle: ↑ airflow velocity in constricted glottis → ↓ pressure.
    • This negative pressure sucks VFs medially, aiding closure (inferiorly first).
  • Mucosal Wave: Rippling of VF mucosa over the vocalis muscle.
    • Essential for clear, resonant voice; assessed by stroboscopy.
    • Reduced/absent in VF stiffness (e.g., scar, sulcus).

⭐ The myoelastic-aerodynamic theory is the most widely accepted model explaining voice production, highlighting the interplay of muscle tension, elasticity, and airflow.

Innervation & Blood Supply - Power & Pipes

  • Innervation (Vagus Nerve - CN X):

    • Superior Laryngeal Nerve (SLN):
      • Internal br: Sensory to supraglottic mucosa (cough reflex).
      • External br: Motor to Cricothyroid m. (VF tensor, ↑pitch).
    • Recurrent Laryngeal Nerve (RLN):
      • Motor: All intrinsic laryngeal muscles (except Cricothyroid); controls VF abduction/adduction.
      • Sensory: Infraglottic mucosa & vocal folds.
      • 📌 L RLN longer (aortic arch); R RLN (subclavian a.).

      ⭐ Cricothyroid m. (pitch elevation) is the sole muscle innervated by External SLN.

  • Blood Supply:

    • Arteries:
      • Sup. Laryngeal A. (from Sup. Thyroid A.): Supraglottis; with Int. SLN.
      • Inf. Laryngeal A. (from Inf. Thyroid A.): Infraglottis; with RLN.
    • Veins:
      • Veins parallel arteries: drain to Sup. Thyroid V. (→IJV), Inf. Thyroid V. (→Brachiocephalic V.).

Laryngeal innervation and vascular supply

High‑Yield Points - ⚡ Biggest Takeaways

  • Vocal folds: 5 layers (Epithelium, Superficial LP/Reinke's space, Intermediate LP, Deep LP, Vocalis muscle).
  • Reinke's space (Superficial LP): key for mucosal wave; site of Reinke's edema.
  • Vocal ligament: formed by Intermediate and Deep Lamina Propria.
  • RLN innervates most intrinsic muscles; SLN (External branch) innervates Cricothyroid.
  • Cricothyroid tenses folds, ↑ pitch; Vocalis muscle forms the fold's body.
  • Voice production relies on Myoelastic-Aerodynamic theory & Bernoulli effect.
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Practice Questions: Vocal Fold Structure and Function

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A patient presents with hoarseness and laryngoscopy reveals a warty, cauliflower-like growth on the vocal cord. Identify the most likely lesion.

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Flashcards: Vocal Fold Structure and Function

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Treatment of adductor dysphonia consists of botulinum toxin injections in the _____ muscle (external part) on one or both sides to relieve spasm.

TAP TO REVEAL ANSWER

Treatment of adductor dysphonia consists of botulinum toxin injections in the _____ muscle (external part) on one or both sides to relieve spasm.

thyroarytenoid

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