ANATOMY AND PHYSIOLOGY OF
THE LARYNX
September 4, 2014
WHY DO WE NEED TO KNOW THE ANATOMY
AND PHYSIOLOGY OF THE LARYNX

A solid understanding of normal structure and
function of the larynx basis for
Evaluating larynx and phonatory function
 Impact of specific pathologies
 Interpretation of evaluation findings
 Development of appropriate voice treatment plans
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LARYNX
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Cartilaginous tube
 Connects to the respiratory system (trachea
and lungs) inferiorly
 Superiorly to the vocal tract and oral cavity
 Position important because of its relationship
and integration between three subsystems
 Pulmonary power house
 Laryngeal valve
 Supraglottic vocal tract resonator and
articulators
LARYNX
Lungs are the power supply for
aerodynamic (subglottic tracheal)
pressure that blows vocal cords apart –
sets them into vibration
 Vocal cords oscillate in a series of
compressions and rarefactions
 Modulate the subglottic pressure or
transglottal pressure of short pulses of
sound energy to produce human voice
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LARYNGEAL VALVE
Complex arrangement of muscles, mucous
membrane, and connective tissue
 Soft tissues responsible for airway preservation
 Cartilage serves as a protective shield and support
 Muscles and cartilages create three levels of folds
or sphincters for communication and vegetative
body functions
 Epiglottis folds posteriorly and inferiorly over
the laryngeal vestibule – separates the pharynx
from the larynx – first line of defense for
preserving the airway
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LARYNGEAL VALVE

Second sphincter is formed by the ventricular
folds (not active during phonation) become
active during hyper function or effortful speech
production and extreme vegetative closure
 Cause increase in intra-thoracic pressure by
blocking outflow of air from lungs
 Tight compression with rapid contraction of
the thoracic muscles during sneezing and
coughing
 Longer durations to stabilize the thorax
during physical tasks (e.g., lifting, childbirth,
defecation, etc.)
LARYNGEAL VALVE
Third and final layer is the true vocal
cords
Vibration for speech production
Close tightly for non-speech and
vegetative tasks such as coughing,
throat clearing and grunting
 Angles of closure are multidimensional
 Horizontal (lateral to medial)
 Vertical
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STRUCTURAL SUPPORT FOR THE LARYNX
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https://www.youtube.com/watch?v=204cBDG4fhU&list=PLB7
8D43E66A2CCBD8&index=5
Larynx is suspended from a single bone – hyoid or
superior border
Six laryngeal cartilages
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Three unpaired (epiglottis, thyroid and cricoid)
Three paired (arytenoid, corniculate, cuneiform)
Thyroid bone articulates with the superior cornu of
the thyroid cartilage via the thyrohyoid membrane
Epiglottis cartilage – leaf shaped- attached to the
inner portion of the anterior rim of the thyroid
cartilage
Made up of elastic cartilage - does not ossify or
harden with age – remains flexible to allow a pliable
free edge to assist in closing airway and diverting
foods and liquids towards the esophagus
STRUCTURAL SUPPORT FOR THE LARYNX
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Thyroid cartilage – three sided, saddle shaped curve
Anterior attachment of the true vocal cords at the
internal rim of the anterior curve
Posteriorly are two cornu or horns that extend
upward to articulate with the hyoid bone and
inferiorly to articulate with cricoid cartilage
Made up of hyaline cartilage that ossifies – limits
flexibility with age
Lateral walls form quadrilateral plates or laminae –
meet in the midline in a thyroid notch or prominence
In newborns, the laminae form a curve of 130 degrees
– angle becomes more acute with age
A fully matured thyroid cartilage is 90 degrees in
males (Adam’s apple) and 110 degrees in females
STRUCTURAL SUPPORT FOR THE LARYNX
Cricoid cartilage – hyaline cartilage – below the
thyroid
 Signet ring shaped – narrow anterior curve and
broad posterior back
 Two sets of paired facets (flat surfaces) that
articulate with adjacent thyroid and arytenoid
cartilages
 The cricothyroid joint connects the lateral edges
of the cricoid to the inferior cornu of the thyroid
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STRUCTURAL SUPPORT FOR THE LARYNX
Cricothyroid joints are positioned on the top of
the posterior cricoid rim
 Both joints are lined with a synovial membrane
(or connective tissue cushion for the joint,
supplies secretions for lubrication, blood supply,
adipose cells and lymph tissue)
 Do not display age related deterioration and
gender differences
 Inferior to the cricoid cartilage are the tracheal
rings
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STRUCTURAL SUPPORT FOR THE LARYNX
 Arytenoid
cartilages are pyramidal
in shape
 Four surfaces – anterior, lateral,
medial and a base
 Anterior angle projects forward at
the base forming the vocal process
 Hyaline cartilage except for vocal
process which is made up of elastin
STRUCTURAL SUPPORT FOR THE LARYNX
Vocal process is the cartilaginous portion of the
vocal folds
 Lateral arytenoid angle is the muscular process –
intrinsic muscles for abducting and adducting the
vocal folds
 Medial angle of arytenoid cartilages faces its
arytenoid pair forms an even surface for midline
glottic closure
 Base is concave to allow smooth articulation with
the humped (convex) surface of the posterior
cricoid cartilage (half cylinder over a bar)
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STRUCTURAL SUPPORT FOR THE LARYNX
Corniculate cartilages (cartilages of Santorini)
are attached by a synovial joint to the superior
tip of the arytenoids
 The cuneiform cartilages (cartilages of Wrisberg)
are embedded in the muscular complex superior
to the corniculates
 Hyaline cartilages
 Add structure and stability to preserve the
airway
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EXTRINSIC AND INTRINSIC MUSCLES
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Extrinsic laryngeal muscles - attached to a site on the
larynx and an external point (hyoid bone, sternum,
mandible or skull base)
Major function – to change the height and tension as a gross
unit (swallowing, lifting, phonating and other vegetative acts)
 Also alter the shape and filtering characteristic of the
supraglottic vocal tract – modifies vocal pitch, loudness and
quality
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Intrinsic muscles – both ends attached within the larynx
Primary function – alter shape and configuration of the glottis
to modify the position, tension and edge of the vocal folds
 Adduction (closing), abduction (opening) and modifying vocal
fold length, tension and thickness
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Both sets of muscles also help with ventilation, airway
protection, communication and laryngeal valving
EXTRINSIC LARYNGEAL MUSCLES
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Suprahyoid (above the hyoid bone) and infrahyoid (below the
hyoid bone)
Identified based on their names which describe their
anatomical attachments
Knowing the attachments one can predict the effect of the
individual muscle contraction (shortening) between the sites
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Stylohyoid (styloid process of the temporal bone to the hyoid bone) raises the hyoid bone posteriorly
Mylohyoid (mandible to the hyoid bone) – raises the hyoid bone
anteriorly
Digastric anterior belly (mandible to the hyoid) – raises the hyoid
bone anteriorly
Digastric posterior belly (mastoid process of the temporal bone to the
hyoid) – raises the hyoid bone posteriorly
Geniohyoid (mandible to the hyoid) – raises the hyoid bone anteriorly
Raises the larynx during swallowing to protect airway
Laryngeal elevation during phonation is a sign of excessive
extrinsic laryngeal muscle tension and a sign of
hyperfunctional voice use
EXTRINSIC MUSCLES OF THE LARYNX
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Infrahyoid muscles
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Sternohyoid (sternum to hyoid bone) – lowers the
hyoid bone
Sternothyroid (sternum to thyroid cartilage) – lowers
the thyroid cartilage
Omohyoid (scapula to the hyoid cartilage) – lowers
the hyoid bone
Thyrohyoid (thyroid cartilage to the hyoid bone) –
shortens the distance between the thyroid and hyoid
bone
Sternocleidomastoid (forms a sheath between the
mastoid process and the sternum)
Lower the larynx in the neck
EXTRINSIC LARYNGEAL MUSCLES
INTRINSIC LARYNGEAL MUSCLES
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5 intrinsic muscles attaches to cartilages to
modify the cricothyroid and cricoarytenoid joint
relationships
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Affect the position, length and tension of the vocal
folds
Changing the position of the cartilage framework
that house the vocal folds
Altering the shape and configuration of the glottis,
the opening between the vocal folds
https://www.youtube.com/watch?v=204cBDG4fhU&li
st=PLB78D43E66A2CCBD8&index=5
http://www.youtube.com/watch?v=jrYkz2TAEpE&list
=PLB78D43E66A2CCBD8&index=6
INTRINSIC LARYNGEAL MUSCLES
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Cricothyroid – broad, fan-shaped muscle –
inferiorly to the cricoid cartilage and superiorly
to the thyroid cartilage – decreases the distance
between the two cartilages – lengthening the
vocal cords
Pars recta (vertical belly)
 Pars oblique (angled belly)
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Reduces the vibrating mass of the vocal folds by
increasing the longitudinal tension, limits the
vibrations to the thinnest portion of the vocal fold
located at the medial edge
 Greatest contributor to the fundamental
frequency control – higher tones
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INTRINSIC LARYNGEAL MUSCLES
INTRINSIC LARYNGEAL MUSCLES
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Thyroarytenoid – attached anteriorly to the internal
angle of the thyroid cartilage and posteriorly to the
vocal process of the arytenoid
Two compartments
Thyromuscularis lateral component – adduction of the
vocal cords – fast acting muscle fibers
 Thyrovocalis (vocalis) medial component – greater control
over phonation – slow acting muscle fibers
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Body of the vocal fold – contraction shortens and
thickens the fold by pulling the arytenoid cartilages
anteriorly and by increasing the mass of the vibrating
medial edge
Lowers fundamental frequency, increases loudness
Control over vocal fold shape, edge and glottic closure
patterns
INTRINSIC LARYNGEAL MUSCLES
INTRINSIC LARYNGEAL MUSCLES
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Lateral cricoarytenoid muscle – broad fan-shaped
muscle – lateral side of the cricoid to the arytenoid
muscular process
Rocks arytenoids anteriorly and slides them laterally
 Redirects the vocal process medially brings the
membranous vocal folds to midline or adduction
 Strongest vocal fold adductors
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Interarytenoid muscles – two bellies
Transverse portion (only unpaired intrinsic laryngeal
muscle) attaches to the posterior plane of each arytenoid
 Oblique portion (crossed bellies) attached at 45 degree
angle from inferior border of one arytenoid to the superior
border of its contralateral pair
 Shortens the distance between the arytenoid cartilages
causing adduction – forceful closure of the posterior glottis
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INTRINSIC LARYNGEAL MUSCLES
Posterior cricoarytenoid – sole abductor of the
vocal folds
 Posterior lamina of the cricoid and the muscular
(lateral) arytenoid cartilage
 Contraction causes abduction (opens) the vocal
folds
 When the arytenoids rock posteriorly to redirect
the vocal processes laterally and separate the
membranous portions of the vocal folds
 Abducts for respiration and quick glottal opening
gestures during unvoiced sound productions
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INTRINSIC LARYNGEAL MUSCLES
INTRINSIC LARYNGEAL MUSCLES
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Exceptional rules
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All muscles are paired (right with a left) except for
the transverse interarytenoid which functions as one
unit, bringing the arytenoid cartilages together
All intrinsic muscles server as adductors except for
posterior cricoidarytenoid muscles or the sole
abductor
All muscles are innervated by the recurrent laryngeal
nerve except the cricothyroid which is innervated by
the external branch of the superior laryngeal nerve
http://www.youtube.com/watch?v=jrYkz2TAEpE&list
=PLB78D43E66A2CCBD8&index=6
http://www.youtube.com/watch?v=66oBTupir2M&list
=PLB78D43E66A2CCBD8&index=7
INTRINSIC LARYNGEAL MUSCLES
VOCAL CORD MICROSTRUCTURE
 Membranous
portion of the vocal folds – 5
histologically discrete layers – vary in
composition and mechanical properties
 Membrane oscillates to create sound
 Integrity of the vibration pattern for
phonation relies on the pliable elastic
structure
 Different layers provide variable amounts
of flexibility and stability
VOCAL CORD MICROSTRUCTURE
5
layers are epithelium, 3 layers of the
lamina propria (superficial, intermediate
and deep) layers, and the vocalis muscle
 Epithelium – mucosal covering of
stratified squamous cells that wraps
over the internal contents, thinnest
layer, consists of 6-8 cell layers,
described as a pliable capsule – needs a
thin layer of slippery mucous
lubrication to oscillate, shiny cord you
see is due to this lining and mucousal
covering
VOCAL CORD MICROSTRUCTURE
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Next 3 layers form the lamina propria
 Loose extracellular tissue (extracellular matrix)
composed of lipids, carbohydrates and specialized
proteins
 The lamina is slightly more dense than the
epithelium but still flexible and loose
 Superficial layer or Reinke’s space is a gelatinlike
soft, slippery substance which allows it to vibrate
significantly during phonation which is violated by
vocal cord pathology
 Intermediate layer is composed principally of elastic
fibers which can stretch to twice its length , this is
what increases the length and therfore the pitch
VOCAL CORD MICROSTRUCTURE
Deep layer of the lamina propria is
still denser and composed of collagen
fibers
Tissues of the third and fourth layers
form the vocal ligament-not present in
the new born – appears between 1-4
years and continues to develop until
maturity at puberty
Deep layer is interspersed by muscle
fibers to join vocalis muscle and the
deep layers together
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VOCAL CORD MICROSTRUCTURE
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The fifth layer or the vocalis muscle
forms main body of the vocal fold
Provides tonicity, stability and mass
It is the only true “active” tissue and
is the only portion of the vocal cord
that can contract and relax in
response to neurologic control
The lamina propria and epithelium
layers vibrate passively in response to
aerodynamic breath support
VOCAL CORD MICROSTRUCTURE
 Extracellular
matrix of the lamina propria
 Composed of fibrous proteins,
interstitial proteins, carbohydrates and
lipids
 Fibrous proteins
consists of elastin and collagen found
in different concentration in different
layers of the lamina and contributes
to the vibratory properties of the vocal
fold cover
VOCAL CORD MICROSTRUCTURE
Elastin fibers predominate in the
superficial and intermediate layers,
collagen in the deep layer
Elastin lets the layers stretch and
then return to its original shape
Collagen does not stretch easily but
tolerates stress but offers strength to
the extracellular matrix
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VOCAL CORD MICROSTRUCTURE
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Interstitial proteins
 Consists of proteoglycens and glycoproteins
 Role in vocal cord vibration is related to
control of tissue viscosity, layer thickness
and internal fluid content
 Hyaluronic acid appears in greater
concentration in the intermediate layer
 Attracts water to form large, space filling
molecules that creates a gel – acts as a
cushion and resists compressive and
shearing forces during vibration
VOCAL CORD MICROSTRUCTURE
Also protects cells from deterioration,
assists in tissue repair and clotting
Exceeds in males to females (3:1); why
men have a lower pitch then women
 Glycoproteins, lipids and carbohydrates
Consists of fibronectin found in
normal and injured vocal cords – plays
a role in wound healing
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VOCAL CORD MICROSTRUCTURE
 Body
cover theory of vocal fold
vibration (Hirano)
 Three vibratory divisions
Cover (epithelium and superficial
layer of the lamina propria)
Transition (intermediate and
deep layer of the lamina propria)
Body (vocalis muscle)
VOCAL CORD MICROSTRUCTURE
The vibrating cover forms the compliant,
fluid oscillation seen in the vocal vibratory
patterns while the body provides stiffer
underlying stability of the vocal fold mass
and tonus
 The transition serves as coupling between
the superficial mucosa and the deep muscle
tissue of the vocal folds during vibration
 Undulation or oscillation of the superficial
vocal fold layers creates a ripple of tissue
deformation and recoil
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VOCAL CORD MICROSTRUCTURE
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Three vibratory phases of wave motion seen in
endoscopy
 Horizontal (medial to lateral movements) as
seen in the open and closing patterns of
vibration – 1-2 mm
 Longitudinal (anterior and posterior –
zipperlike wave) seen in front-to-back
travelling wave 3-5 mm
 Vertical phase (inferior to superior opening
and closing of the vocal folds) as seen in an
upper versus lower lip differences – mostly
unseen
 https://www.youtube.com/watch?v=66oBTupir
2M&list=PLB78D43E66A2CCBD8&index=7
FOLDS AND CAVITIES OF THE LARYNX
Major folds are true vocal folds
 Superior and lateral to the true folds are the false
or ventricular folds
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Do not actually vibrate in normal voice production
except at very low fundamental frequency (below 50
Hz)
 Few muscle fibers – very difficult to regulate their
tension, mass and length
 Aryepiglottic folds form a sphincter enclosing the
entrance to the larynx
 During swallowing and protective acts these folds
contract to reduce the diameter of the laryngeal
entrance to protect the airway
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FOLDS AND CAVITIES OF THE LARYNX
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Supraglottal cavity
Lies above the vocal folds
 Superior border is the aryepiglottic sphincter
 Acts as a resonator of the sound produced by the
vocal cords
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Subglottal cavity
Lies beneath the vocal folds
 Lower boundary is the first tracheal ring
 Pressure increases beneath the closed vocal folds
until it becomes sufficient to force the folds open and
begin phonation
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FOLDS AND CAVITIES OF THE LARYNX
 Ventricles
Paired cavities lying above and slightly
lateral to the true vocal cords
 Opening is very small and little effect
on the sound produced
 However in some conditions of singing
the opening is sufficient to permit
meaningful resonance adding to the
glottal tone
 http://www.youtube.com/watch?v=sFU
mm5I_0P0
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DEVELOPMENTAL CHANGES
Newborns the larynx is situated high in the neck
– cricoid positioned at the level of C3 to C4
 Newborns breathe only through nasal passages
in the first few months of life allowing them to
breathe and swallow simultaneously
 During the first year the larynx begins its
descent in the neck as the pharynx lengthens and
widens
 By puberty the larynx is at the level of C6 or C7
 Accompanied by skeletal facial growth and
development, creates an expanded vocal tract
which contributes a drop in fundamental
frequency
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DEVELOPMENTAL CHANGES
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Intrinsic larynx also undergoes dramatic changes
from birth through puberty
Vocal fold length of boys and girls is similar until 10
years
Gradual and consistent gender development changes
vocal cord length and ratio between membranous to
cartilaginous portions of the vocal cords
In males with the rise in testosterone at puberty
stimulates the anterior growth of the thyroid notch
and wide growth of the pharynx
In newborns have no vocal ligament (intermediate
and deep layers of the lamina propria) and therefore
little stability, the greater ratio of cartilage to
membrane length provides protection of the airway
(vocal ligament emerges between 1-4 years)
DEVELOPMENTAL CHANGES
GERIATRIC VOCAL FOLD
Deterioration in voice quality, pitch and loudness
range and endurance among geriatric speakers
 Common appearance of thinned (bowed) vocal
folds in elderly patients with no other pathology
except advanced chronological age
 Described by the term “presbylaryngeus”
 Intermediate layer of the geriatric vocal folds was
observed to be looser and thinner causing loss of
tissue bulk, resulting in bowed appearance
 Studies confirm that the lamina propria
decreases in flexibility and elasticity with age
due to increased cross-linking of fibers
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PHYSIOLOGY OF PHONATION
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Theory of vibration
Based on physical process of flow-induced oscillation
 A consistent stream of air flows past the tissues creating a
repeated pattern of opening and closing
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Van den Berg’s aerodynamic myoelastic theory
At the onset of phonation, subglottal pressure rises as
expiratory forces are met by resistance from the adducted
vocal folds
 When the pressure rises to overcome the resistance the
folds are blown and subglottal pressure diminishes
creating an increase in flow through the glottis
 Because air pressure and flow are inversely proportional,
when flow increases, air pressure decreases between the
vocal folds (Bernoulli Principle)
 The elastic tissue recoil pulls the vocal cords back toward
midline completing the cycle of vibration
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PHYSIOLOGY OF PHONATION
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Self oscillating system by Titze
 Respiration is the driving force that sets the vocal folds
in motion and kept in motion as follows:
 In the subglottal region the leading edge of the vocal
folds are blown apart and set into motion by
subglottic pressure and translaryngeal (glottal flow)
is positive
 Intraglottal space or the small space directly between
the vocal folds – intraglottal pressure keeps the vocal
folds oscillating by alternating exchange of airflow
and pressure peaks – when the vocal cords close the
pressure is negative but rises as the air flow is cut off
by the closing glottis
PHYSIOLOGY OF PHONATION

Supraglottal air column located at the outlet of
the glottis immediately above the vocal folds – air
molecules are compressed or rarified in a delayed
response to the alternate pressure and flow puffs
modulated by the vibrating vocal folds (molecules
are pushed and released in response to the sound
energy pulses released from the oscillating vocal
folds) causing transfer of energy from the fluid or
air pressure to the tissue or upper lip of the vocal
folds and assists in sustaining the oscillation
MECHANISM OF VOCAL FREQUENCY
CHANGE
The physical properties that determine the
frequency of a vibrating string also determine the
vibrating frequency of the vocal cords
 Determined by length, tension and mass
 Total mass is not important but the mass
vibrating is more important
 Amount of mass set into vibration depends upon
fundamental frequency, intensity and mode of
vibration and length of the vocal cord
 As the band is stretched, the thickness of the
band decreases
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VOCAL FOLD LENGTH AND FUNDAMENTAL
FREQUENCY
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Three voice register with respect to pitch
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In the pulse register vocal folds are closed 90% of the cycle
(60Hz)
In the modal register, as the vocal length increases,
frequency increases
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Vocal cords are closed 50% of the time
In the falsetto or upper register the fundamental frequency
appears to decrease as vocal fold length is increased
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Pulse register or glottal fry
Modal register
Falsetto
Opposite to that predicted by that of a vibrating string
The vocal cords also do not seem to adduct completely
during phonation
Length is not the sole mechanism of fundamental
frequency
VOCAL FOLD TENSION AND FUNDAMENTAL
FREQUENCY
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As tension increases the frequency increases (similar
to that of a string)
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Difficult to measure tension
Indirect evidence must be obtained
Largest variations occur in the upper frequencies or in the
falsetto register
Very little variation in the frequencies heard in speech
Tension is not the only determinant but mass per unit
length has a pronounced influence on the fundamental
frequency of vibration
In the modal register the mass is an important factor
however, in the falsetto register, tension is a
determinant factor
Mass per unit length more important than just
tension or mass
VOCAL FOLD MASS AND FUNDAMENTAL
FREQUENCY
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Vocal frequency decreases as mass increases
(similarly to the vibrating string)
FREQUENCY AND AIR FLOW
Airflow is another contributing factor – sign of an
inefficient system
 The speed of the airflow also causes variations in
frequencies in voice production
 However excessive airflow makes the system
inefficient resulting in breathiness
 All three factors important in voice production

Mass
 Tension
 Air flow
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MECHANISM OF LOUDNESS CHANGE
Wide range of vocal intensities (exceeding 60 dB)
 Additional changes of intensity result from
variation in the size and shape of the vocal tract
which acts as a resonator
 Combination of airflows and pressure
 Increased pressures below the vocal folds when
released by the folds would produce a greater
intensity
 Controlling mechanism of vocal intensity is not
subglottal air pressure rather it is degree and
time of closure of the vocal folds
 Maintaining closure of the vocal folds there is
more time to build up pressure beneath them
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MECHANISM OF LOUDNESS CHANGE
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More intense sound results when the subglottal air
pressure is sufficient to overcome the resistance of the
vocal folds
The more vocal fold resistance there is to opening the
greater the pressure disturbance when the resistance
is overcome and folds are forced to open
Intensity is often controlled by the vocal folds through
variation of glottal resistance (which is ratio of the
pressure divided by the airflow)
Glottal resistance is a major controlling factor in the
lower frequencies
At higher frequencies (in the falsetto range) airflow
becomes a major variable
Very little variation of intensity in the falsetto range
MECHANISM OF LOUDNESS CHANGE
Intensity is also dependent upon velocity of
closure of the vocal folds
 Glottal power is directly related to the rate of
change of the airflow pulse at the moment of the
closure
 This rate of change of airflow is called airflow
closing slope
 Steeper the slope the greater the increase in
frequency
 Intensity control therefore depends upon two
factors – glottal resistance and rate of airflow
change at the moment of closure
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MECHANISM OF LOUDNESS CHANGE
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In an attempt to speak at a normal vocal intensity,
patients increase air pressure by increasing the
expiratory force from the thorax-abdomen system
The patient may attempt to increase glottal closure in
an effort to increase glottal resistance and to
maintain an adequate level of tension in the vocal
folds
These increase in muscle activity causes vocal fatigue
as well as excessive air rushing across the vocal folds
(causing an increase in noise levels)
Vicious cycle ensues, vocal fatigue results in poorer
vocal fold adduction and the greater need for even
greater effort on the patient’s part leading to poorer
voice
MECHANISMS OF LOUDNESS CHANGE
Variation of the frequency composition of a tone
also varies its intensity
 Adding frequencies or varying the amplitude of
the components of the tone affects the intensity
of the complex tone
 Spectrum of the vocal folds can be varied (within
limits) and thus alter the overall intensity of the
vocal fold tone
 Speed of closure affects the spectral features of
the glottal tone
 Number of frequency components in the
pathological voice is smaller than in the normal
voice
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MECHANISMS OF LOUDNESS CHANGE
Lower intensities are used to compensate for the
different spectral characteristics and their effect
on intensity
 A patient may also try to increase subglottal
pressues or adductory forces – results in an
increase in strain and abuse to the vocal folds
 Loudness is the perceptual correlate of intensity
but intensity is not the only factor that affects
loudness
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Pitch of the voice and its spectral composition also
affects perceived loudness
 Other factors include distance from the speaker,
room acoustics, interference at may affect the
loudness of a voice as perceived by a listener
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MECHANISM OF QUALITY VARIATION
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Identifies an individual and sets him or her apart
from another
Spectrum determines voice quality
It refers to number and amplitude of the frequencies
present in a complex tone (vocal fold tone)
Vocal fold produces many different vocal qualities
each with its own spectral characteristics
Shape and configuration of the vocal tract (length,
cross-sectional area, ratio of oral to pharyngeal cavity
size, etc.) determine the voice quality
Physiological changes in laryngeal and vocal tract
configuration produce different voice qualities
Change in voice quality can signal benign or a life
threatening condition
NEUROANATOMY OF THE VOCAL
MECHANISM
Volitional control rests in the brain
 Many points in the cortex, subcortical areas,
midbrain, and medulla play an important role in
the ultimate control of phonation
 Cerebral cortex responsible for conceptualization,
planning and execution of speech act including
phonation
 3 major areas of cortex responsible for
vocalization
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Precentral and postcentral gyrus (Rolandic area)
 Anterior (Broca’s) area
 Supplementary motor area
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NEUROANATOMY OF THE VOCAL
MECHANISM
 Speech
can be initiated, stopped,
slurred or distorted
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Result of stimulation in the dominant
or non-dominant hemisphere
 Control
of the motor acts occur in the
cortex, individual muscle control
occurs at a much lower level
NEUROANATOMY OF THE VOCAL
MECHANISM
 Subcortical
mechanisms
 Motor cortex has numerous connections
to the thalamus, metathalamus,
hypothalamus, epithalamus, and
subthalamus
 Thalamus has numerous connections to
the cerebellum and midbrain
 Ventral lateral nucleus of the thalamus
was responsible for initiating speech
movements, control of loudness, pitch,
rate and articulation
NEUROANATOMY OF THE VOCAL
MECHANISM
Thalamus acts as not only a relay
station but is also involved in
maintenance of consciousness,
alertness, attention and integration of
emotion into the speech act
 Thalamus also integrates sensory
information, coordinating outgoing
information from the cortex and other
areas of the brain and adding the
emotionality to speech and voice
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NEUROANATOMY OF THE VOCAL
MECHANISM
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Midbrain structures
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Structures that connect the cerebrum with the
brainstem and spinal cord
Four rounded areas called colliculi on the posterior
surface
Superior colliculi assoicated with vision
Inferior colliculi concerned with audition
Stimulation of the cavity or cerebral aqueduct of
Sylvius and grey matter dorsal to the aqueduct or
periaqueductal gray (PAG) produces activity in the
laryngeal muscles
Lesions in this area also causes mutism
Control muscles of respiration, vocalization and
orofacial region
NEUROANATOMY OF THE VOCAL
MECHANISM
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Brainstem
Nucleus ambiguus, nucleus tractus solitarii, reticular
formation have connections to the motor roots of the
vagus and the PAG area
 Neurons in this area responsible for control of
respiration
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Cerebellum
Control and planning stages of a movement
 Without this control the cerebral cortex could not
function and would be ineffective
 Acts to regulate motor movement continuously and
regularly
 Coordinates muscles of the larynx
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PERIPHERAL CONNECTIONS: THE VAGUS
NERVE
Vagus provides sensory and motor fibers
 Start in the caudal portions of the nucleus
ambiguus
 Vagus emerges from the surface of the medulla
between the cerebellar penduncle and the inferior
olives in the midbrain and exist the skull through
the jugular foramen
 After exiting the skull, the vagus divides into
many branches that serves the head, neck,
thorax and abdomen
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PERIPHERAL CONNECTIONS: THE VAGUS
NERVE
After exiting a small filament or the meningeal
filament exits the nerve to serve the Dura mater
on the posterior fossa of the base of the skull
 The auricular branch provides sensory fibers to
the skin behind the pina and to the posterior par
of the external auditory meatus
 The pharyngeal branch provides motor fibers to
the muscles of the pharynx and the soft palate
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PERIPHERAL CONNECTIONS: THE VAGUS
NERVE
The major portions of the vagus serving the larynx
are the superior laryngeal and recurrent laryngeal
nerves
 Superior laryngeal – primary sensory nerve – arises
from the inferior ganglion of the vagus and descends
along the side of the pharynx behind the internal
carotid artery where it sends off two branches
 The external branch descends along the side of the
larynx to serve the cricothyroid muscle
 The internal branch descends to an opening in the
thyrohyoid membrane and enters the larynx to serve
the mucous membrane of the larynx down to the true
vocal folds
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PERIPHERAL CONNECTIONS: THE VAGUS
NERVE
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The recurrent laryngeal nerve follows a different
course on either side of the body
On the right side the recurrent descends in the neck
to loop around the subclavian artery (just below the
clavicle) and then ascends alongside the trachea to
serve the remaining intrinsic muscles of the larynx
On the left side the recurrent laryngeal nerve takes a
more circuitous route
Descends into the thorax, loops around the aorta and
then ascends alongside the trachea until it reaches
the larynx
It provides motor fibers to the remaining intrinsic
laryngeal muscles
PERIPHERAL CONNECTIONS
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The extrinsic muscles of the larynx are
innervated by several nerves
Anterior belly of the digastric – mylohoid branch of
the inferior alveolar nerve
 Posterior belly of the digastric – 7th cranial nerve
(facial)
 Mylohyoid muscle – mylohyoid branch of the inferior
alveolar nerve
 Geniohyoid, sternohyoid, sternothyroid, and
omohyoid by the ansa cerivcalis
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PERIPHERAL CONNECTIONS
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Protective reflexes of the larynx used to protect
the airway and sustain life
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Sensory endings collect information from larynx and
respiratory system
Transmit this information through reflexes arcs and
directly to the CNS
Responds to changes in mechanical forces and air
pressure
Send information to the CNS as well as to the joints
of cartilages that discharge
Affect the electrical activity of some intrinsic
laryngeal muscles
Stretch receptors in the muscles also discharge when
the muscle is stretched or contracts