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Glottis Anatomy and Function: The Gateway to the Airway

The Glottis: Structure and Physiologic Role

The glottis is the opening between the true vocal folds (vocal cords) within the larynx. It is the critical valve regulating airflow between the pharynx and trachea.

Anatomy

  • Location: Midline larynx, at vertebral level C3-C6
  • Boundaries: True vocal folds (medial), arytenoid cartilages (posterior)
  • Components: Membranous (anterior 3/5) + cartilaginous (posterior 2/5) portions
  • Epithelium: Stratified squamous (vocal folds) → respiratory (trachea)

Key Functions

FunctionMechanismClinical Relevance
PhonationAdduction → Bernoulli effect → mucosal wave → soundVoice disorders, paralysis, nodules
Airway protectionReflex closure (laryngeal adductor reflex) to swallowing, irritantsAspiration prevention
RespirationAbduction (PCA muscle) → low resistance airflowBilateral abductor paralysis = airway emergency
Valsalva / Effort closureComplete adduction → increased intrathoracic pressureDefecation, lifting, childbirth
Cough reflexDeep inspiration → glottic closure → explosive expirationAirway clearance

Neural Control

  • Recurrent laryngeal nerve (RLN): All intrinsic muscles EXCEPT cricothyroid
  • Superior laryngeal nerve (SLN): Cricothyroid (tension), sensory above folds
  • Vagus (CN X): Parent nerve

Clinical Assessment

  • Laryngoscopy (flexible/rigid): Visualize glottic configuration, mobility
  • Stroboscopy: Mucosal wave analysis
  • EMG: Denervation patterns

Pathology Examples

  • Vocal fold paralysis (RLN injury: thyroid surgery, lung cancer, idiopathic)
  • Laryngospasm (inappropriate closure)
  • Laryngeal stenosis (scarring, intubation trauma)
  • Laryngeal cancer (glottic most common)

The glottis is the final common pathway for voice, breathing, and airway protection — a triad of vital functions.

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