Laryngeal Histopatholgy
1
Development of voice
• Birth:
-larynx has higher anatomical
position
-6th level of the cervical region
-pitch of neonate= 700 Hz
• 2 years:
-soft cartilage's & lax ligaments
(susceptible to collapse)
-ossification of hyoid bone
2
• 5 years:
-larynx assumes position C7
-pitch decreases
• 20 years:
-hardening of the cricoid
• 30 years:
-hardening of the arytenoid
• 65 years:
-ossification of all cartilage's except
the cuneiform & corniculate
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Four voicing signals in the neonate
• Birth Signal-short duration (1 sec.)- vowel pattern
• Pain Signal-long in duration, high-pitched
-strained harsh quality
• Hunger signal-rising & falling of pitch; glottal signal
• Pleasure Signal-more nasal, pitch variability, glottal
quality
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Differences: Female & Male voices
• Prepubescent-
-minimal, similar pitch
• Puberty-females v.f.’s 4mm & male 8-10mm
-thyroid angle is 120 °in females & 90 ° in males
-v.f.’s enlarge & epiglottis flattens in both female &
male
-v.f. mucosa becomes less transparent
-tonsils & adenoids atrophy
5
Geriatric vocal folds
• Deterioration in pitch, loudness range,&
endurance
• v.f.’s appear thin & bowed
• “aging larynx”= Presbylaryngeus
• Breakdown of collagenous & elastic fibers
• Intermediate layers of v.f.’s are looser &
thinner
• Bowed appearance during glottal closure
• Thickening of superficial layer of lamina
propria.
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Vocal Fold Microstructure
• Membranous portion of v.f.’s
is intricate & layered,
• There are 5 histologically
discrete layers,
• Layers vary in composition
and mechanical properties,
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Histologic Layers
• 5 histologic layers from most
superficial to most deep are:
– epithelium
– lamina propria (3 layers)
• superficial layer
• intermediate layer
• deep layer
• vocalis muscle
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Vocal Ligament
Epithelium
Lamina Propria
superficial layer
intermediate layer
deep layer
Vocalis Muscle
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Frontal section through membranous portion
epithelium
lamina propria
-superficial
-intermediate
-deep
vocalis muscle
conus elasticus
epithelium
lamina propria
-superficial
-intermediate
-deep
vocalis muscle
conus elasticus
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Epithelium
• Thin mucosal covering of
squamous cells
• Wraps around internal contents of
v.f.’s
• No mass, totally compliant
• Needs thin layer of mucous
lubrication to ossilate best.
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Lamina Propria
• Consists of three layers:
superficial layer-composed of loose fibrous matrix
(known as Reinke’s space)
-composition described as soft gelatin
-intermediate layerintermediate layer-composed of elastic fibers and has
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slightly more mass
deep layer– Denser still, composed of collagenous
fibers
• Tissues of 3rd & 4th layers together
are known as the vocal ligament
• The vocal ligament develops
throughout childhood until the larynx
reaches full maturity (puberty)
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Vocalis Muscle
• Fifth layer
• Main body of the vocal fold
• Provides stability and mass
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5 layers
• Layers change from superficial to
deep, mass gradually changes &
compliance
• Epithelial; most elastic
• Subsequent layers form a complex
transition
• Finally, stiff deep muscle tissue
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The Body-Cover Model
• Theory developed by Hirano (1974)
• Model explains extreme variability in voice
production
• Model explained:
-Cover :(epithelium & superficial layer of
the lamina propria)
-Transition:(intermediate and deep layer of
the lamina propria)
-Body : (vocalis muscle)
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• Cover:
1)epithelium
2) lamina propria
-superficial
• Transition
intermediate
deep
• Body
vocalis muscle
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More on Body-Cover
• Characteristics of v.f. vibration dependent on:
-length
-elastic properties
-mass distribution
• body contraction/ vocalis contraction= the
cover becomes shortened and thicker giving
more mass to the length unit
• cover is entirely passive; longitudinal state is
specified by its length & lateral displacement
depends on the thickness of its body.
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Some clinical observations
• CT and vocalis activity are weak: movement
of body & cover are identical,
• Vocalis activity is strong and the CT is weak:
movement is greater for the cover rather than
body,
• CT is active and vocalis is relaxed: both the
body & cover are equally stiffened, movement
is minimal (e.g. Falsetto).
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Laryngeal Histopathology
• Before we speak of trauma to the
structures of voicing, it is important to
know the fine structures it is composed
of, that which makes it vulnerable.
• We have talked about general categories
of structure (i.e. cartilage’s & muscles)…
….Next is the histology of the larynx:
The Tissue Structure.
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Histology
• Cartilage's are made up of two different
types of tissue
• Thyroid & Cricoid= Hyaline cartilage
• Epiglottis, cuneiform & corniculate= Elastic cartilage
• Hyaline: thin, dense collagenous fiber
(protein based)
• Elastic: elastic fibers
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Histological structure differences
• v.f. layered structure varies along length
• How does the membranous portion of the v.f.
connect to the cartilaginous framework?
-Anterior end:
*macula flava (a mass of elastic fibers,
attached to ant. commissure)
-Posterior end:
*post. macula flava (attached directly to
arytenoid cartilage)
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Function of Macula Flava
• Protects the membranous portion
of the vocal folds during vibration
from mechanical damage.
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Structure in Newborns
• Epithelium is similar to adults
• Major difference: lamina
propria is thick relative to its
v.f. length (adult’s thinner)
• No vocal ligament
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Vocal Fold Growth
• Immature macula flava in newborns (more
susceptible to damage),
• Immature vocal ligament appears at 4 years
(still very thin & does not contact vocalis
muscle),
• 3 layers of lamina propria don’t exist until the
ages 6-12,
• Thickness of cover and lamina propria
increase with age,
• Intermediate lamina propria gets thinner with
age,
• Deep layer of lamina propria gets thicker.
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Summary: Thickness
1) Cover thickest at midportion
2) Lamina propria thinnest at
midportion; lamina propria thickest
at the two ends, ant. & post. macula
flava
3) Vocalis muscle thicker than mucosathinner in the ant. end & thicker at
post. end
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Changes: Age
1) Cover gets thicker - not epithelium but
superficial layer of lamina propria,
2) Superficial layer of lamina propria
becomes swollen,
3) Elastic fibers become looser, especially in
males 40 years and older,
4) Great individual differences in changes
of v.f. structure.
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Disorders: Cover, Transition & Body
• Epithelial Cover
1) Hyperplasia- atypical cell growth
(squamous), either hypo- or hyperdysplasia.
• Superficial layer of lamina propria
1) Vocal Fold Nodules- typically bilateral,
edemous, white bumps, cover mass &
thickness increase, develop on vocal fold
edge, ant. 1/3.
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Disorders Cont...
2) Vocal Fold Polyps- vocal fold edge, red or
white, small or large, sessile or pedunculated,
usually unilateral, asymmetrical,
-Mass of cover increase
-Cover stifness increase with bleeding &
proliferation of collagenous fibers
-Edema only, then decrease cover stiffness
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Activity
• Clinical Execise:
Tommy is a 13 year old boy who was
in a car accident. He has several
neurological deficits, as a result of a head
injury. Tommy has limited movement of
his abdominal muscles and external
superior laryngeal nerve damage. He is
currently in speech therapy with the
following symptoms:
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• falsetto voice quality (high pitched, not due to
prepubescent voice quality)
• cannot sit up in bed, however with support can
be elevated to sitting position
• breathy quality voice (air escaping through
vocal folds)
• all extrinsic and most intrinsic muscles are in
tact.
• seems out of breath while speaking
• frequently takes recovery breaths
• complains of pain in and around his larynx
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Questions?
• What muscles, cartilages are affected or
damaged in the larynx and elsewhere in the
body?
• Determine exact nerve and muscle
involvement.
• Why is his pitch high, voice breathy?
• Why does he run out of air and have to take
recovery breaths?
• What can we do for this patient?
• Prognosis for recovery?
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Readings
• Ch. 3 Colton (Laryngeal Histopathology)
• Additional Reading: “Cover-BodyTheory of Vocal Fold Vibration” By
Daniloff
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Directed Reading
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Directed reading summary
• Breathing apparatus is made up of:
-pulmonary system (lungs & airways)
-chest wall system (rib cage, abdomen &
diaphragm)
• Pulmonary system is “passive”- no skeletal
muscle
• Chest wall contains numerous skeletal muscles
– rib cage: both insp. & exp. muscles
– abdomen: expiratory muscles only
– diaphragm: inspiratory muscle
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Thoracic Expansion
Diaphragm
Vertical
Anteriorposterior
Transverse
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Diaphragm/Abdominal Movement
Diaphragm
Abdominal
Wall
Pelvis
Inhalation
Exhalation
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Relaxing
• Upright:
Inspiration:
1) chest wall expands (lungs inflate)
2) diaphragm flattens, pushes abdominal
contents outward (creating larger space in
thoracic cavity)
Expiration:
1) Gravity pulls down on rib cage (recoil)
making it smaller
2) diaphragm recoils back to the dome shape
3) abdomen actively pushes contents back into
place.
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• Supine:
Inspiration:
1) driven by diaphragm, no abdominal
involvement
2) rib cage has little elevation (fighting
gravity)
Expiration:
1) driven by recoil forces alone
2) abdomen expired by gravity
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Speaking
• Upright:
Inspiration:
1) accomplished by diaphragm
2) ribcage elevates (lungs inflate)
3) abdomen is active to “tune” the diaphragm
by providing a relatively firm base to contract
against
Expiration:
1) Abdomen is main expiratory muscle
2) Abdomen pushes on the diaphragm & thus
deflates lungs and generates pressure to speak
on
3) rib cage also slowly descends with muscular
help
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• Supine:
Inspiration:
1) driven by the diaphragm
2) abdomen is non-active
3) rib cage expands against gravity
Expiration:
1) driven by rib cage, recoil and muscular
resistance allows us to speak
2) abdomen is nonactive (already in
expiratory position)
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Voice: Perception, Vibration,
Myoelastic-Aerodynamic Theory,
Bernoulli
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Laryngeal Functions
1) Valving for life:
1. Breathing
2. Swallowing
3. Pressure activities (sneezing, coughing, lifting etc.)
2) Valving for speech:
1. Mechanics of voiceless sounds
-Whispering & voiceless consonants
2. Mechanics of glottal vibration
-vibratory cycle
3. Vibratory forces
3) Mechanics of voice control
1. Register
2. Pitch
3. Loudness
4. Quality
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Valving: Life
• Breathing
1. Airway open (all three valves:
false, true, supra cavity)
2. True open to different degrees
-quiet respiration (intermediate
position)
-forced (lateral position)
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Valving: Life
• Swallowing
1. Reflex mechanism:
-pulls the larynx up against base of
tongue & squeezes arytenoid
cartilage's against epiglottis
*this action closes laryngeal inlet
to Supraglottal cavity & pulls
esophagus open to receive bolus.
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Valving: Life
• Pressure Activities
1. Sneezing, coughing, defecating,
childbirth, lifting all require alveolar
pressure)
2. Compression of air by respiratory
pump & laryngeal valving to resist the
escape of air
3. Need airway resistance to build
pressure!
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Valving: Speech
• General
– requires modified use of laryngeal valve,
– inherited a pressure reflex that has evolved for the
unique requirements of speech,
– v.f.’s adduct just enough to initiate vibration,
– laryngeal resistance for voice is so refined that it
can be controlled to produce changes in pitch &
loudness from syllable to syllable.
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Valving: Speech
• Mechanics of voiceless sounds
1. voiceless consonants- laryngeal valve is
open, can be resisted by tongue, lips etc.
2. whispering- no voice, v.f.’s do provide
resistance,
-special whisper adjustment: vibrating
glottal edges are stiff but do not touch (no
vibration), the arytenoid cartilage's form a
“glottal chink” (whisper triangle) to permit air
to flow through glottis without v.f. vibration.
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The Glottis- Whispering
Whispering Triangle
Cartilaginous
Glottis
Muscular Glottis
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Valving: Speech
• Mechanics of glottal vibration
1. vibratory cycle- single vibration of the vocal
folds,
-”Begins when subglottal pressure (Ps )
overpowers fold resistance just enough for the
v.f. to first blow open.”
*opening phase: v.f. continue to blow apart
* closing phase: air escapes, reduces Ps
enough for fold resistance to overpower
airflow, then close.
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Glottal Cycle
opening phase
closing phase
open phase
closed phase
• Arrows represent driving air pressure changes
• Notice that the vocal folds are always in
transition
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Valving: Speech
• Mechanics of glottal vibration cont.
1. Two ratios to describe the features of
vibration:
* Speed quotient (SQ)- ratio of the
durations of the opening phase to the
closing phase (opening/closing).
* Open quotient (OQ)- ratio of the
duration of openness to the duration of
the entire cycle (open/entire cycle)
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Valving for speech cont...
• Mechanics of glottal cycle cont.
1. v.f.’s vary in compliance (how absorptive of
force they are) & vary in complexity of
vibratory movement
* Vertical Phase Difference: v.f.’s open
upward to outward; from bottom to top &
back to front
* Also, another vibratory complexity is the
motion of the mucous membrane covering
the true vocal folds.
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Movement of vocal folds
Anterior
Posterior
Spread of glottal opening
Superior
Inferior
Vertical Phase difference
• Note how the vocal folds open from bottom to
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top & back to front.
Valving: Speech
• Vibratory Forces
1. Aerodynamic-myoelastic theory of phonation-
“Glottal vibration is a result of the
interaction between aerodynamic forces
& vocal fold muscular forces.”
*Aerodynamic forces-Bernoulli Effect: as velocity of a gas
or liquid increases, pressure
decreases.
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Bernoulli Effect
• Trachea & laryngeal airway as
a freeway
• molecules of air= cars
• closer the molecules (cars),
slower they move
Molecules
• faster they move the farther
apart they are spaced (lower
pressure)
• faster air moves through glottis,
farther molecules are apart &
exert less force on v.f.’s
Compressed
molecular
traffic56
Valving: Speech
• Vibratory Forces cont.
* Myoelastic Forces-The opposing myoelastic
(muscular & elastic tissue)
forces provides the vertical
phase difference essential for
phonation.
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* Myoelastic component cont.1) The glottal edge, particularly the loose mucosal
covering functions as two separate but
interconnected masses, one below the other,
2) These two masses are actually the upper &
lower portions of the mucous membrane & the
underlying vocalis muscle,
3) When lower portion is pushed aside by air
pressure, the upper portion is dragged along,
4) The strength of the connection between these
two masses is the mechanical coupling stiffness58
Mechanical Coupling Stiffness
• Upper & lower
portions work together
(coupled),
• Remember: The
masses are the vocal
folds,
• One of several
muscular forces
involved with
phonation.
Upper
Mass
Lower
Mass
Upper Mass
Lower Mass
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Other muscular Forces
• All provide resistance to airflow1) Stiffness or “longitudinal tension”- inc. in
muscle stiffness increases resistance; elongation
merely thins vocalis muscle,
2) Mass resistance- thickness in vocalis muscle,
more mass in folds the more force required to
blow them apart,
3) Viscous forces- more viscous the folds, the
more they decrease velocity of movement; inc..
resistance to aerodynamic forces
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Summary of Aerodynamic-Myoelastic
Theory
• “v.f. vibrations are dynamic
interchanges of intraglottal
pressure between the folds that
force them apart and their
mechanical resistance to this
pressure.”
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Summary Cont...
• Beginning of glottal cycle:
1) Intraglottal pressure exceeds atmospheric pressure
above the folds & forces open a small glottal chink,
2) Air flows through the chink; molecules are slow in
the trachea than increase velocity traveling through
the glottis (i.e. Bernoulli slide),
3) Air molecules accelerate and start to move farther
apart,
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4) Pressure against upper portion of the folds decreases, but
remains high against the lower portion (where molecules are
still compressed in a “traffic jam”),
5) Therefore, the upper glottis is not blown open by pressure
but “dragged” along by the stiffness of mechanical coupling,
6) Lower potion is where the intraglottal pressure forces the
folds apart,
7) Aerodynamic force continues to open the glottis,
8) Closure when resistance exceeds intraglottal pressure.
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Valving: Speech
• Mechanics of voice control*Voice can be controlled for:
1) Pitch
2) Loudness
3) Quality
4) Register
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Valving: Speech
• Mechanics of voice control1) Register:
-The mode of adjustment of the larynx
by which voice is produced.
-Speech is produced almost always in
one register, whereas singing many more.
Three main registers:
1) modal
2) falsetto
3) pulse
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Modal Register
•
•
•
•
•
•
•
•
register used for speech
produces low fund. frequencies (Fo)
also called “chest” or “heavy” register
vocal folds are short & thick
stiffness low
amplitude of vibration is large
folds tend to completely close
signal is rich in harmonics
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Falsetto Register
•
•
•
•
•
•
•
•
•
“light” register
produces higher range of Fo’s
vocalis is lax
cricothyroid activity adjusts length
longer, thinner, stiffer folds (compared to
register)
small amplitude of vibration
incomplete closure of v.f.’s
fewer higher harmonics
shutter-like appearance
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Pulse Register
•
•
•
•
“vocal fry” or “glottal fry”
low frequency register
sounds rough or deep
used infrequently for speech or
singing
• short, thick & lax vocal folds
• complex vibratory pattern
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Valving: Speech
• Mechanics of voice control cont.-
2) Pitch:
-physical correlate is fundamental
frequency,
-Women’s Fo=180-250 Hz;
-Men’s Fo= 100-150 Hz
-pitch is variable,
-average Fo changes during the first 20
years, than stabilizes.
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Pitch: Vocal Fold Thickness
• Pitch is determined
by rate of vibration,
• Male folds are
longer & thicker,
• v.f. thickness
changes correlate
better to pitch than
length,
• But...stiffness from
lengthening is the
main determiner of
pitch.
Low
Pitch
High
Pitch
70
Valving: Speech
• Mechanics of voice control cont.3) Loudness:
-Listener's response to the amount
of energy in a sound.
-Physical correlate = intensity,
-Varies with volume & velocity of
air, higher fundamental =greater
loudness,
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Loudness cont...
• Greater the volume velocity of each glottal
pulse the greater the loudness,
• Intensity increases as alveolar and subglottal
pressures increases, inc. air escapes
• Glottal resistance increases with intensity
(pressure can not rise without an equal
increase in resistance)
• Louder the tone, longer vocal folds stay
closed.
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Loudness
Soft
volume
velocity
Loud
Alveolar
pressure
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Valving: Speech
• Mechanisms of voice control cont.4) Quality:
-distinctive characteristics of a tone,
exclusive of its pitch & loudness,
-3 distinct qualities:
1) Breathiness
2) Harshness
3) Hoarseness
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Breathiness
• Glottal adjustment offers enough resistance for
vibration,
• Laryngeal adjustments:
1) in the front- v.f.’s close but don’t touch,
however close enough to generate tone and...
2) in the back- glottal chink present which lets air
escape to an excessive extent and...
3) excessively large glottal area in each cycle
(large volume of air flow at low velocities)
• Folds barely close folds, low intensities
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Harshness
• “roughness”
• Associated with “gravely” voice
• Cause is irregularity in v.f. vibration
• Frequency variability= “jitter”
• Amplitude variability= “shimmer”
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Hoarseness
• Combines both breathiness &
harshness
• Irregular vibratory patterns in
which leakage is excessive
• Early warning sign of vocal pathology
• Aperiodic vibration
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The End!!!
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