1. Laryngeal Structure & Function; Vocal Fold Vibration
2/8/00

2. Vocal Folds 5 layers of tissue (deep= muscle)
Glottis= space between the vocal folds
Subglottal= area below the vocal folds
Located at the end of the airstream at superior end of traches

3. Structural Support of the Larynx
Larynx is suspended in the neck by a single bone, the hyoid bone.
There are 6 laryngeal cartilage's:
3 paired
3 unpaired
provide structural support for the larynx.

4. Laryngeal Cartilage's 3 Unpaired Cartilage's -Thyroid -Cricoid
-Epiglottis
-Thyroid
-Cricoid

5. 3 Paired Cartilage's
-Cuneiform
-Corniculate
-Arytenoid

6. Larynx & Trachea Tracheal Ring Hyoid Bone Thyoid Cartilage
Crioid Cartilage

7. Laryngeal Cartilages Thyroid Thyroid Notch Superior horn Cricoid
Vocal Ligament
Superior horn
Stretched
Cricoid
Inferior horn

8. Arytenoid Movement
Rocking
Gliding
Adducted
Abducted

9. Extrinsic Laryngeal Muscles
Three Main Purposes:
1) Fixation (primary role)
2) Elevation (move larynx up)
3) Depression (move larynx down)
Two major groups of extrinsic muscles
Suprahyoid & Infrahyoid
Anatomical position:
Suprahyoid- one of the above attachments lies above the larynx.
Infrahyoid- one of the attachments lies below the larynx.

10. Extrinsic laryngeal Muscles
Mandible
Mastoid Tip
Mylohyoid
Hyoid Bone
Sternohyoid
Omohyoid
Sternum
Ant.
Digastric
Post.
Digastric
Stylohyoid
Thyrohyoid
Sternothyroid

11. Intrinsic Laryngeal Muscles
Functions:
1) Abduction of the vocal folds for respiration,
2) Fine discrete movements during voice production & closure of the vocal folds and,
3) Protection of the trachea.

12. Intrinsic Muscles: Pars recta
Action of Cricothyriod
Pars oblique
Pars recta
Cricothyroid: fan-shaped, 2 divisions, Lengthens & tenses the vocal folds.

13. Intrinsic Muscles Vocal ligament Thyroarytenoid
Thyrovocalis
Thyromuscularis
Thyroarytenoid: muscle making up the true vocal folds, 2 parts: thyrovocalis (bound to the vocal ligament) & thyromuscularis (lateral to arytenoids).

14. Intrinsic Muscles Action of Post. Cricoarytenoid Posterior
Posterior Cricoarytenoid: Abducts the vocal folds, actively contracted at the end of phonation & any speech sound not requiring v.f. vibration.

15. Intrinsic Muscles Action of Lat. Cricoarytenoid Lateral Cricoarytenoid
Lateral Cricoarytenoid: lies along upper surface of cricoid cartilage, adducts vocal processes of arytenoids closing membranous portion of v.f.’s.

16. Intrinsic Muscles
Transverse
Interarytenoids
Oblique
Interarytenoids
Interarytenoids (transverse & oblique): Unpaired, 2 part muscle, adducts the v.f.’s in the cartilaginous portion by pulling arytenoid tips together.

17. The Glottis
Glottis
The glottis is an open space between the vocal folds.
Size is dependent on what position the v.f.’s are in.
Not a muscle or cartilage.
Abduction- open v.f.’s; Adduction- closed v.f.’s

18. Vocal Fold Vibration

19. Phonation Subglottal pressure develops Folds begin to vibrate
Phonatory threshold is reached
3 cm H20 (.3 kPa) - 6 cm H20 (.6 kPa)
Folds begin to vibrate
Lower subglottal pressure keeps vibration going
Subglottal air pressure pushes the vocal folds laterally & superiorly to initiate vibration
Continuing cycles are sustained by the recoil forces of V.F’s & aerodynamic forces

20. Surface Wave Posterior Top = Coronal section
Bottom = Motions of upper and lower margins (Superior view)

21. Vocal Cord Vibration

22. Vertical & Horizontal Movement of Vocal Fold Vibration
Anterior
Posterior
Spread of glottal opening
Superior
Inferior
Vertical Phase difference
Note how the vocal folds open from bottom to top & back to front.

23. Cover Body Theory of Phonation
Vocal adjustments are regulated by changing mechanical properties of the layers of tissue in the vocal folds
Two primary Layers:
Cover (surface of folds)
Body (deeper in the fold)
Layers change in stiffens by different muscle activity

24. Two-Mass Model Upper Mass Lower Mass Upper Mass Lower Mass
Two masses connected by a spring
Vibratory pattern has horizontal &
vertical components
Mechanical (elastic) forces
Body responsible for lateral motion
Cover responsible for surface-wave behavior
Upper
Mass
Lower
Mass
Upper Mass
Lower Mass

25. Regulation of Fundamental Frequency
Longitudinal tension = regulation of frequency
Laryngeal muscle adjustments (change length & tension)
f0 = 1/2L (T/r) 0.5
T= Tension of vocal fold mucosal cover,
r = Density of the tissue & L = Length of folds
F0 is determined primarily by tension of the vocal fold cover and not by length

26. Regulation of Intensity of Phonation
What determines vocal intensity?
Subglottal pressure
Pressure increases & airflow increases through the glottis
Threshold (3-6 kPa= dB SPL)
Conversation (below 10 cm H20)
Loud conversation (up to 50 cm H20)
Intensity increases:
Amplitude increases
Longer closed phase of vocal vibration

27. Amplitude of Soft & Loud Vocal Fold Vibration

28. Other Laryngeal Functions
Vocal fold opening: inspiration, silent pause, whisper, voiceless sounds
Medial compression: excessive closure for lifting, childbirth, defecation