Applied Physiology of the Larynx
Functions
- Protection of the lower air passages
- Respiration
- Phonation
Protection of the Lower Air Passages
- Closure of the laryngeal inlet
- Closure of the glottis
- Cessation of respiration
- Cough reflex (forced expiration is made against a closed larynx)
Phonation
- Voice is produced by vibration of the vocal cord
- Source of energy is the airflow
- Normal vocal fold vibration occurs vertically from inferior to superior
- The mouth, pharynx, nose, chest (resonating chambers)
Respiration
- Vocal cord in abduction position
Voice Mechanism
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Speaking involves a voice mechanism that is composed of three subsystems:
- Air pressure system
- Vibratory system
- Resonating system
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The “spoken word” results from three components of voice production:
- Voiced sound, resonance, and articulation
Voiced Sound
- The basic sound produced by vocal fold vibration (“buzzy sound”)
Resonance
- Voiced sound is amplified and modified by the vocal tract resonators (throat, mouth cavity, and nasal passages)
Articulation
- The vocal tract articulators (the tongue, soft palate, and lip) modify the voiced sound
Vocal Cord Vibration
- Vocal folds vibrate rapidly in sequence of vibratory cycles with a speed of about:
- 110 cycles per second (men) = lower pitch
- 180 to 220 cycles per second (women) = medium pitch
- 300 cycles per second (children) = higher pitch
- Louder voice: increase in amplitude of vocal fold vibration
- Bernoulli effect
Laryngeal Sphincters
- True vocal cord
- False vocal cord
- Aryepiglottic sphincter
