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Understanding Vocal Cords: Anatomy, Function & Voice Production

The vocal folds (commonly called vocal cords) are paired, flexible bands of tissue within the larynx (voice box) that vibrate to produce sound. They are essential for speech, singing, airway protection, and coughing.

Anatomy

  • Location: Within the thyroid cartilage (Adam's apple), spanning anteroposteriorly.
  • Layers (Histological):
    • Cover: Stratified squamous epithelium (non-keratinized) + superficial layer of lamina propria (Reinke's space — loose, pliable, critical for vibration).
    • Transition: Intermediate & deep lamina propria (elastin, collagen fibers) — provide elasticity & tensile strength.
    • Body: Thyroarytenoid (vocalis) muscle — bulk, tension control.
  • Attachments: Anterior → thyroid cartilage (via anterior commissure). Posterior → arytenoid cartilages (mobile).
  • Blood Supply: Superior & inferior laryngeal arteries. Rich vascularization.
  • Innervation: Recurrent laryngeal nerve (RLN) → all intrinsic muscles except cricothyroid (external superior laryngeal nerve). Sensory: internal branch SLN (above cords), RLN (below).

Sound Production (Phonation)

  1. Adduction: Lateral cricoarytenoid (LCA) + interarytenoid (IA) muscles rotate/slide arytenoids → vocal folds midline.
  2. Airflow: Subglottic pressure builds (expiratory effort).
  3. Vibration (Mucosal Wave): Air pushes folds apart → Bernoulli effect + tissue elasticity sucks them closed → repeating cycle (100–1000+ Hz).
  4. Pitch (Frequency): Determined by length, tension, mass of folds. Cricothyroid (CT) muscle lengthens & tenses → higher pitch. Thyroarytenoid (TA) shortens & thickens → lower pitch.
  5. Loudness (Intensity): Subglottic pressure + medial compression.
  6. Quality (Timbre): Shaped by vocal tract (pharynx, oral cavity, nasal cavity) resonance — formants.

    7. Non-Phonatory Functions

    • Airway Protection: Adduct during swallow (laryngeal elevation + epiglottic deflection).
    • Cough Reflex: Deep inspiration → glottic closure → pressure build → explosive abduction → high-velocity expulsion.
    • Valsalva Maneuver: Glottic closure + abdominal contraction → ↑ intrathoracic pressure (defecation, lifting, childbirth).
    • Effort Closure: Stabilize thorax for heavy lifting.

    Common Disorders

    • Laryngitis (acute/chronic) — inflammation, edema.
    • Vocal fold nodules/polyps/cysts — phonotrauma.
    • Vocal fold paralysis/paresis (RLN injury).
    • Presbyphonia (age-related atrophy, bowing).
    • Reflux laryngitis (LPR).
    • Papillomas (HPV), dysplasia, carcinoma.

    Vocal Hygiene

    • Hydration (2–3 L water/day).
    • Avoid vocal strain (shouting, whispering, excessive talking).
    • Limit caffeine, alcohol, reflux triggers.
    • No smoking/vaping.
    • Warm-up/cool-down for voice users.
    • Seek ENT/SLP if hoarseness >2–3 weeks.

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