Physiology

Three Zones of Laryngeal Airway Protection

1. Epiglottis and A-E Folds

2. False Folds

3. True Folds: most significant Laryngeal Sensory Innervation

• Internal Branch of the SLN: innervates the laryngeal mucosa above the glottis

• RLN: innervates the laryngeal mucosa inferior to the glottis

• Negative Pressure Receptors: SLN, maintains patency of airway during inspiration

• Airflow Receptors: cold receptors, stimulated from moving air

• Drive Receptors: proprioception

• Laryngospasm: exaggerated ADduction reflex caused by laryngeal irritation (reflux, foreign bodies, extubation, mucus); may be driven by the CNS, mediated by the superior laryngeal nerve

• Cardiovascular Collapse: bradycardia and hypotension caused by laryngeal irritation (intubation); uncertain mechanism

Voice Production

• Requirements for Sound Production: source of energy (eg, airflow) and source of vibration (eg, true vocal folds, neoglottis, articulator constrictions)

• Myoelastic-Aerodynamic Theory: true vocal folds are ADducted and tensed, subglottic pressure increases until level of pressure induces vocal fold vibration, which opens the glottis from an inferior to superior direction and closes from an inferior to superior direction

• Bernoulli's effect: forced air across a constricted zone produces negative pressure, allowing the true vocal folds to be "sucked" back together

• normal vocal fold vibration occurs vertically from inferior to superior, and horizontally along the superior surface of the vocal fold from medial to lateral

Components of Speech

• Phonation: production of voice, determined by vocal fold position, expiratory force, vibratory capacity of vocal folds, vocal fold length and tension

• Resonation: oral/nasal speech balance, determined by velopharyngeal musculature valving and by structure of the chest, nasopharynx, nasal cavity, and oral cavity

• Articulation: production of speech sounds, determined by actions of the lips, tongue, and jaw musculature activity

• Respiration: production of source of energy (airflow dynamics) for verbal speech, determined by inhalation/exhalation respiratory muscular activity

• Prosody: production of syllable stress, emphasis, and inflection patterns to provide affective speech tone, influenced by phonatory, articulatory, and respiratory forces

Voice Parameters

• Pitch (Hz): perceptual term, related to frequency of vocal fold vibration (Hz); determined by the length, tension, and speed of vibration of the vocal folds

• Fundamental Frequency: predominant pitch component of the speaking voice, 128 Hz ("C" below middle "C" note) in males (long, thick vocal folds) and 256 Hz (middle "C" note) in females (short, thin vocal folds)

• Loudness (decibels): the intensity of the voice; determined by subglottic pressure, glottal resistance, airflow rate, amplitude of vocal fold vibration, and force of vocal contact

• Quality (Timbre): determined by the synchronicity of vocal fold vibration and glottal competence

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