Larynx Anatomy for Vocal Production

1. Phonatory SystemLecture 8

2. The Larynx (Anatomy Review) • Bone • Cartilage • Ligament • Membrane • Muscle

3. The Larynx • Innervation • Extrinsic muscles • Intrinsic muscles • How the vocal folds vibrate • Initiating vibration • Pitch • Registers

4. Innervation • Vagus (CN X) • Superior laryngeal nerve: • Cricothyroid (CT) • Recurrent laryngeal nerve: • Thyroarytenoid (TA) • Posterior Cricoarytenoid (PCA) • Lateral Cricoarytenoids (LCA) • Interarytenoids (IA) Blumenfeld, H., 2002, Neuroanatomy through Clinical Cases, Sinauer, Inc.

5. Extrinsic Laryngeal Muscles • Many extrinsic laryngeal muscles • Thyrohyoid • Elevates larynx • Sternothyroid • Depresses larynx Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 112.

6. The Larynx • Innervation • Extrinsic muscles • Intrinsic muscles • How the vocal folds vibrate • Initiating vibration • Pitch • Registers

7. Thyroarytenoid • Bulk of the vocal folds • Contractions can result in: • Shortening the vocal folds • Pulling thyroid and arytenoid cartilages toward each other • Increasing the tension of the vocal folds • Isometric (contracting and not changing length) • Shorten: decreases pitch • Increase tension: increases pitch Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 98.

8. Cricothyroid • When it contracts, it helps to lengthen the vocal folds • It elevates the cricoid arch, and depresses the thyroid lamina (shortens the space between the cricoid and the thyroid) • This can help to increase pitch Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 97.

9. TA and CT: Activation Patterns • CT active and TA passive = increase pitch • Increase length • Increase stiffness • TA active and CT passive = decrease pitch • Decrease length • Decrease stiffness • TA and CT contract simultaneously = increase pitch • Increase stiffness

10. Posterior and Lateral Cricoarytenoids • Work in opposition • PCA: • Rocks arytenoids away from midline • Opens the vocal folds • LCA: • Rocks arytenoids toward midline • Closes the vocal folds Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 100.

11. ABduction & ADduction • PCA: • Rocks arytenoids away from midline • ABducts the vocal folds • LCA: • Rocks arytenoids toward midline • ADducts the vocal folds Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 107.

12. Interarytenoids • Transverse: • Pulls arytenoids toward each other • ADducts the vocal folds • Oblique: • Tips one arytenoid (apex) toward the other (body) • ADducts the vocal folds Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 101.

13. The Larynx • Innervation • Extrinsic muscles • Intrinsic muscles • How the vocal folds vibrate • Initiating vibration • Pitch • Registers

14. Vocal Fold Vibration • Many theories of vocal fold vibration • Myo-elastic aerodynamic theory of vocal fold vibration • Nonuniform tissue movement: Multimass models

15. Myo-elastic aerodynamic theory • Van den Berg, 1958 • Based on Bernoulli equation: P + ½ pv2 = constant • P = pressure • p = fluid density • v = velocity • Please use this formula- I believe the formula in your book is incorrect. • This equation states that as pressure increases, velocity decreases (assuming density is constant) Based on Titze, I.R. (2000). Principles of Voice Production.

16. Myo-elastic aerodynamic theory • Van den Berg, 1958 • Based on Bernoulli equation: P + ½ pv2 = constant • Basics of this theory: • When the vocal folds are closed, pressure builds in the subglottal region • When the pressure is high enough, it forces the vocal folds open • The vocal folds continue to open further as air rushes out • Once they reach a maximum opening, the elasticity in the vocal folds pulls them together • The cycle repeats

17. Nonuniform tissue movement: Multimass models • Other theories in between, but this is the most recent • Explains self-sustained oscillation: as the vocal folds continue to oscillate (vibrate), they are able to sustain the same velocity and width of excursion Titze, I.R. (2000). Principles of Voice Production.

18. Nonuniform tissue movement: Multimass models • Upper and lower parts of the vocal folds do not move as one • The lower part of the vocal folds moves first, followed by the upper part • Convergent: lower further apart than upper • Divergent: upper further apart than lower Titze, I.R. (2000). Principles of Voice Production.

19. The Larynx • Innervation • Extrinsic muscles • Intrinsic muscles • How the vocal folds vibrate • Initiating vibration • Pitch • Registers

20. Initiating vibration • Phonation threshold pressure (PTP): smallest subglottal pressure needed to start self-sustained oscillation • For low frequency phonation, PTP is around 3-4 cm H20

21. Pitch and Registers • Average pitch: • Women: 220 Hz • Men: 130 Hz • Registers • Chest (Low pitches) • Middle/Mixed (Middle pitches) • Head/Falsetto (High pitches) Zemlin, pg 166.