revised review of phonatory physiology

PhonationPhonation

Muscle Review & Physiology

Key Laryngeal CartilagesKey Laryngeal Cartilages

Thyroarytenoid/VocalisThyroarytenoid/Vocalis

Thyroarytenoid/Vocalis LocationThyroarytenoid/Vocalis Location

PCA & InterarytenoidsPCA & Interarytenoids

PCA ActionPCA Action

Interarytenoid ActionInterarytenoid Action

LCALCA

LCA ActionLCA Action

CricothyroidCricothyroid

Cricothyroid ActivityCricothyroid Activity

Cricothyroid Location and ActionCricothyroid Location and Action

Laryngeal PhysiologyLaryngeal Physiology

• The vibrating vocal folds are the major source of periodic sound for speech. The vocal folds may also produce aperiodic sounds.

• In this section, we discuss two main aspects of phonatory physiology:– 1. How are the vocal folds put into vibration?– 2. How do we change the manner in which the

vocal folds vibrate?

Glottal Tone InitiationGlottal Tone Initiation

• Before sound can be produced from the vocal folds, several conditions must be established:

• 1. The vocal folds must be approximated or at least brought into the phonatory position. Phonation may also be initiated after complete closing of the vocal folds.

• 2. It is also necessary to properly tense and elongate the vocal folds prior to actually producing sounds. Length and tension are important determinants of the fundamental vibrating rate of the vocal folds.

• 3. Finally, there must be airflow from the lungs. In order to be able to produce the required flow of air from the lungs, there must be a sufficient quantity of air in the lungs.

• Once the aforementioned conditions have been met, phonation can start.

The Phonatory Cycle: The The Phonatory Cycle: The Aerodynamic-Myoelastic Aerodynamic-Myoelastic

TheoryTheory• The vocal folds are brought to the midline

of the glottis via muscular forces.• Vocal fold adduction must occur in

coordination with the expiratory air stream.• Subglottal air pressure builds below the

closed folds.• The pressure eventually overcomes the

resistance of the folds and separates them.

The Bernoulli ForceThe Bernoulli Force

• The vocal folds return to the midline of the glottis due to (a) elasticity, and (b) the Bernoulli force:– When a gas/fluid moving through a tube

reaches a constriction, its velocity increases.– As the gas speeds through the point of

constriction, a pressure drop occurs perpendicular to the direction of flow.

• The vocal folds are sucked back together in this zone of low pressure.

Fluid Flow Through a Fluid Flow Through a ConstrictionConstriction