Phonation: Physiology

Question 1

Theory that states that the vocal folds vibrate because of the forces and pressure of air and the elasticity of the vocal folds

Answer 1

Myoelastic - Aerodynamic Theory

• air flowing out of lungs is temporarily stopped by closed (nearly closed) vocal folds
  
  • this builds up subglottal air pressure
  • > blows VFs apart > sets VFs into vibration
• air then moves with increased velocity through glottal opening
  
  • > pressure between edges of VFs decreases
  • > VFs are sucked together
  • https://youtu.be/Yku2HrGnORw

Question 2

Occurs when the velocity of a gas or fluid increases when it passes through a constriction, decreasing the pressure of the gas or fluid.

Answer 2

BERNOULLI EFFECT

• In phonation, the Bernoulli effect is caused by increased speed of air passing bet. VFs (the constriction)
  
  • resulting in decrease in pressure between the VFs which causes the “sucking” motion of the VFs toward one another.
• The subglottal air pressure builds up and sets the folds in motion (Myoelastic-Aerodynamic theory)
  
  • = cycle of opening and closing of the VFs repeated more than 100 times per second during vocalization

Question 3

MUCOSAL WAVE ACTION

https://youtu.be/BPqx3GqAcmM

Answer 3

• the cover (epithelium and superficial lamina propria aka Reinke’s space) & the transition (intermediate and deep layers of the lamina propria) over the vocalis muscle slide and produce a wave.
• The wave travels across the superior surface of vocal fold about 2/3 the way of the lateral edge of the fold
• Generally wave dissipates before reaching inner surface of thyroid cartilage.
• Without mucosal wave, there is no vibration = no phonation
• VFs that have been stripped surgically to remove abnormal growths (e.g. nodules) may be stiff and vibrate inefficiently due to alteration of the normal mucosal wave