Physiology and neuroanatomy of phonation by Dr Abdullah PG ENT SSIMS Davangere Karnataka India

1. Physiology And Neuroanatomy Of
PHONATION

2. Coronal section of larynx
Rima glottidis
Membranous VF
Cartilagenous VF

3. Characteristics of Vocal Fold Layers
Epithelium (stratified squamous)
superficial – interstetial fluid
scattered elastin fibres
Lamina propria
intermediate – elastin fibres
deep – collagen
Thyroarytenoid muscle
vocal lig
thicker anteriorly & posteriorly

4. MUSCLES

5. Abductor
Posterior cricoarytenoid

6. Adductors
• Lateral cricoarytenoid
• Interarytenoid
• Thyroarytenoid (external part)

7. Tension control
• Cricothyroid
• Vocalis

8. Innervation of Larynx

9. Periaqueductal grey matter (PAG) in midbrain
• Integration of cortical and subcortical aspects of language
• generate specific respiratory and laryngeal motor
patterns fundamental to human speech and singing
• production of emotional or involuntary sounds
Subcortical representation reflex laryngeal function & involuntary phonation
Cortical loci voluntary phonation

10. Voluntary Vocalization
Precentral Gyrus (Motor Cortex)
corticobulbar tract
(part of the pyramidal system or
'direct activation' tract)
X XIIX
Decussation
Reticular formation
UMN
governs groups of
muscles
connect with other
cranial nerves
thus controlling
articulation,
phonation and
respiration

11. prephonatory tuning  voluntary cortical control
phonatory modulations  reflex control
laryngeal mechanoreceptors  respond to phanaory activity
Flow receptors – during normal respiration
tracheostomy
Drive receptors – in muscle spindle
phonatory modulation
Freq following fibres – stimulus – vc vibration
Freq non-following fibres
Subglottic mucosal mechanoreceptors – mucosa
Articular mechanoreceptors – capsules of joints
Myotatic mechanoreceptors – muscle spindles

12. MASS 1/fundamental freq
Cricothyroid contraction - ↓ses mass
Ȣ
STIFFNESS tension
serves as the effective restoring force in vibration
Body Cover
cricothyroid ↑ ↑
vocalis ↑ ↓
VISCOSITY - measure quantifying the resistance to tissue deformation
↑viscosity - ↑ subglot pressure to initiate phonation
(phonation threshold pressure)
Affected by
• Hydration levels
• ↑tension - ↑viscosity
Ȣ

13.  At rest (quiet respiration)
 vocal folds abduct on inspiration
 slightly adduct on expiration
 Vocal folds move up and down slightly with the outflow and
inflow of respiratory air
 They are drawn wide apart (full abduction) in forceful
inspiration

14. INITIATION OF VOICE
• Prephonatory inspiratory phase
vocal folds rapidly abduct to allow the intake of air.
• Subsequently, vocal folds are adducted by the contraction of
lateral cricoarytenoid muscles
The vocal note is generated by pulmonic air (air from the lungs)
as it is exhaled between the adducted vocal folds
• Vocal folds – working together – constitute a vibrator-
activated by the excitor (exhaled air)

15. • Subglottic air pressure increases below the adducted vocal
folds until it reaches a level which overcomes their resistance
and blows them apart  vibratory cycles  phonation
• Repeated vibratory movement of vocal folds  production of
vocal note (vocal fold oscillation)
• The amount of air pressure required to begin voicing –
“phonation threshold pressure”

19. THE VIBRATORY CYCLE
• 3 phases: adduction, aerodynamic separation and recoil
• Increased subglottic pressure  overcomes resistance of
adducted vocal folds  vocal fold peel apart from their inferior
border  separation of superior margin  release puff of air
• Bernoulli effect  negative pressure in the glottis  vocal
folds closing rapidly as they are sucked together (inferior margin
closing first)
• Contact between the vocal fold increases until subglottic air
pressure is high enough to blow the vocal folds apart again and
the cycle recommences
Each cycle of adduction, separation and recoil is the manifestation of a mucosal
wave travelling from the inferior to the superior surface of vocal folds
In relation to the vocal tract, Maran describes it as follows,
‘When air passes from one large space to another (e.g. from lung to pharynx),
through a constriction (the glottis), the velocity will be greatest and
the pressure least at the site of the constriction.’

20. Myoelastic–Aerodynamic Theory
Introduced by Johannes Muller 1839
Air from the lungs passing through the glottis causes vibration of
essentially passive vocal folds.
• Myoelastic - vocal fold tension and elasticity
• Aerodynamic - role of fluid dynamics.
Van den Berg modified in 1958
• vocal folds be sufficiently approximated and that the vocal folds
are driven into oscillation by forces that can be explained by
Bernoulli’s principle

21. Body-Cover Theory
• helps to explain mucosal wave
• cover - stratified squamous epithelium and the superficial
layer of the lamina propria (Reinke’s space)
• pliable, elastic, and nonmuscular
• body - intermediate and deep layers of the lamina propria
(vocal ligament) - more fibrous than the superficial layer
• stiffer and has active contractile properties - allow
adjustment of stiffness and concentration of the mass
• mucosal wave occurs in loose cover
• changes in stiffness or tension in the VC alters mucosal wave
↑stiffness in the fold with contraction of the cricothyroid
muscle  velocity of the wave ↑  pitch ↑

22. The period of vocal fold contact and lack of contact in one vibratory cycle

23. • Glottal stop - Adductor muscles can forcibly stop the vocal
folds from moving
• Glottal attack - The abrupt release by the adductor muscles.
Neurochronaxic theory (1950s)
Raoul Husson French scientist &voice enthusiast
which incorrectly advanced the notion that the central
generation of recurrent laryngeal nerve impulses produced cord
vibrations by active contraction of the thyroarytenoid muscles

24. 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

25.  Requirements for normal phonation
 Active respiratory support
 Adequate glottic closure
 Normal mucosal covering of the vocal cord
 Adequate control of vocal fold length and
tension.

26. Fundamental freq
Factors
• Mass
• Stiffness
Muscular control by
• Cricothyroid ↔
• Thyroarytenoid →←
Prephonatory glottal width
↑ - ↑ phonation threshold flow – breathy voice
↓ - pressed vice
Vocal Fold Contour
convergent divergent rectangular
• low phonation threshold
• high vocal efficiency
• Post puberty in boys

27. Symmetry
• Slight asymmetry is very common
• Tension asymmetry  irregular vibratory patterns
Eg, u/l sup laryngeal nerve palsy
PHONATION THRESHOLD PRESSURE
PHONATION INSTABILITY PRESSURE
Phonation Range
Mass lesions
arise due to mechanical injury created by vocal fold collision
m – mass , A – amplitude , F0 - fundamental freq

28. Pitch
• Frequency of glottal signal: Number of vibratory cycles per
second. (Hz)
• Pitch- psychological/ perceptual correlate of frequency
• Habitual pitch- frequency of vibration habitually used by an
individual
• In general, men's vocal folds can vibrate from 90 - 500 Hz,
average about 115 Hz in conversation.
• Women's vocal folds can vibrate from 150 -1000 Hz, average
about 200 Hz in conversation.
• Vocal folds vibrate faster as they're pulled longer, thinner, and
more taut and vibrate more slowly when they're shorter,
thicker, and floppier.
• The cricothyroid muscle and thyroarytenoid muscle
coordinate with each other to create different pitches

29. Vocal loudness
 Perceptual correlate of amplitude is determined by
the size of oscillation of vocal folds .
 Determined by force of trans glottal air flow.
 Shimmer: short term variance in intensity of vocal
signal is called shimmer or amplitude pertubation.
 It indicates characteristics of dysphonic speaker

30. Vocal Registers

31. Recurrent leryngeal nerve palsy
Presbylaryngis
Vocal fold scar
Dehydration and Edema
1
2
3
4
Glottic Insuffeciency

32.  Incomplete adduction of vocal folds during phonation will
result in audible air leakage and breathy voice quality.
 Whisper occurs when there is insufficient vocal fold
adduction to achieve vibration, but sufficient adduction to
produce audible turbulent air.
 An irregular mucosal wave form vibration will result in an
aperiodic sound that will be perceived as hoarse.
 A pressed or strained voice quality occurs when the vocal
folds are strongly adducted (often with supraglottic muscular
involvement) and there is raised subglottal air pressure .

33. The Ideal Larynx
 symmetric
• Mass
• Tension
 rectangular conformation
 Self-sustaining oscillation at low subglottal pressure and
capable of sustaining it over a wide range of pressures and
frequencies
 Vibration of mucosal wave form would produce a perfectly
periodic sound signal.
 Sound would contain a fundamental frequency and its
harmonics.

34. Voice Therapy and Rest
A common goal of voice therapy
↓
reduce intensity
↓
reduce vocal fold collision force and stress
Persons with hoarseness may be speaking with high subglottal
pressure, chaotic vibration, and irregular amplitude.
↓
high impact stress
Avoiding undue stress by not speaking can provide healing time
and prevent worsening of the underlying cause of dysphonia.