Functions of larynx

Function of Larynx

1. Functions of Larynx
Fuad Ridha Mahabot
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2. Introduction
Functions of larynx:
•to protect the airway (sphincteric action) during swallowing and by its
sensitivity
•as a valve – control air pressure and air flow
•as a vibrator – generating sound
* both functions are of fundamental importance during breathing, weight bearing
and phonation
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3. Swallowing (Deglutition)
•Primary function – prevent food and liquid entering the airway
•Sphincteric action of aryepiglottic fold, true and false cold – occurs
simultaneously with elevation of larynx
•Swallowing: Oral stage, pharyngeal stage
•Oral stage (voluntary control): Oral preparatory, Oral transport
Food bolus manipulated by tongue  broken down by teeth  propelled
towards oropharynx
•Pharyngeal stage:
Initiated as the bolus reaches the back of the tongue
Glottis closed by adduction of arytenoids dan contraction of lateral
cricoarytenoids, false vocal cords and true vocal cords
Vocal fold adduction: ~2.3 seconds
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4. Epiglottis: covers laryngeal entrance and directs bolus in two parts into
valleculae and pyriform sinuses
The two columns of the divided bolus meet at the upper border of the relaxed
cricopharyngeus muscle  allow food to enter oesophagus
Rapid laryngeal elevation produces a drop in pressure and transient negative
pressure in the cricopharyngeal sphincter as the bolus passes from the
pharynx into the oesophagus
If laryngeal elevation impaired  pressure drop is slower  negative
pressure does not occur  swallowing problems
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5. Coughing
•Process by which material is expelled from the airway
•Preceded by rapid inspiration  forceful closure of both vocal and
vestibular folds
•Diaphragm ascends spasmodically  Air pressure built up below the
adducted folds  Folds separate explosively  mucous / foreign
material expelled
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6. Effort Closure
•Laryngeal structure has evolved in order to contain intrathoracic
pressure - provide stable fulcrum for the upper limbs
•During any form of exertion involving use of arms, vocal folds are
firmly adducted preventing expulsion of air and collapse of chest wall
 providing a fixed origin for the arm and the shoulder muscles
Post laryngectomy patient / laryngeal paralysis – may have
difficulty with weight-bearing activities
•Effort closure also occurs during childbirth and defaecation 
abdominal contents are compressed by abdominal muscles in order
to achieve expulsion
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7. Biomechanics of Phonation
•At rest (quiet respiration): vocal folds abduct on inspiration and
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
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
Wyke B. Neuromuscular control systems in voice production. In: Bless DM, Abbs JH (eds). Vocal fold
physiology. San Diego: College Hill Press, 1983: 71-6.
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8. •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)
•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”
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9. 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
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11. •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 fold alters the mucosal wave
 stiffness in the fold with contraction of the cricothyroid muscle 
velocity of the wave   pitch 
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
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12. •The period of vocal fold contact and lack of contact in one vibratory
cycle
Phase Description
Closing The vocal folds begin to close rapidly from their lower margin
Closed The medial edges of the vocal folds are in full contact
Opening The vocal folds begin to separate from their lower margin and
gradually peel apart
The superior margin remains in contact until the end of this
phase
Opened The vocal folds are separated, the longest part of normal
vibratory cycle
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•Vocal fold have to be structurally and functionally symmetrical
•Insufficient approximation (glottal insufficiency)  air wastage 
breathy voice

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14. Thank You
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