Motor Speech and Voice Disorders

Anatomy and Physiology

What are the three subsystems of voice production?

1. Respiration (pulmonary power supply)

2. Phonation (laryngeal valve)

3. Resonance (supraglottic vocal tract resonator)

Lungs

The power supply by providing aerodynamic (subglottal) tracheal pressure that blows the VFs apart to vibrate. Vocal oscillation is the sound source for phonation. 

Vocal tract

Serves as the resonating cavity which shapes and filters acoustic energy to produce sound/voice.

What is the primary muscle of inspiration?

The diaphragm: A dome-shaped muscle attached to the inferior border of the rib cage, active in both quiet and speech breathing. When it contracts, it depresses the abdomen and increases the vertical dimensions of the lungs and thoracic cavity.

Which cartilages form the framework of the larynx?

Thyroid, cricoid, arytenoids, epiglottis, corniculates and cuneiforms.

What joint allows pitch change by lengthening the VFs?

cricothyroid joint - tilting the thyroid cartilage forward lengthens and tenses the VFs

Which intrinsic laryngeal muscle is the primary pitch changer?

Cricothyroid

Which muscle is the main vocal adductor?

lateral cricoarytenoid

Which muscle abducts the VFs?

Posterior cricoarytenoid

What muscle forms the body of the VFs?

Thyroarytenoid - including the vocalis whichfine-tunes tension

What are the layers of the VFs?

1. Epithelium

2. Superficial lamina propria - Reinke’s space (vibrates the most)

3. Intermediate lamina propria

4. Deep lamina propria

5. Thyroarytenoid muscle

Myoelastic-aerodynamic theory of phonation

Voice results from…

Myoelastic: VF elasticity + tension.

Aerodynamic: subglottal pressure + Bernoulli effect > VFs open/close in a self-sustaining cycle.

Bernoulli effect in phonation

airflow through a narrow space > pressure drops > VFs sucked together

What determines pitch?

VF length (longer = higher)

VF tension (tenser = higher)

VF mass (more = lower)

What determines loudness?

Subglottal pressure - increased amplitude of vibration = louder voice

What nerve innervates the larynx?

Vagus nerve

RN > all intrinsic muscles except CT

SLN > CT + sensory to supraglottis

Source-filter theory

source = VF vibration

filter = vocal tract

speech = source shaped by filter

Mucosal wave

wave-like ripple of the epithelium