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Laryngeal Histopatholgy

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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

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• 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

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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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Epithelium

Lamina Propriasuperficial layerintermediate layerdeep layer

Vocalis Muscle

Vocal Ligament

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Frontal section through membranous portion

epitheliumlamina propria

-superficial-intermediate-deep

vocalis muscleconus elasticus

epitheliumlamina propria

-superficial-intermediate-deep

vocalis muscleconus 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 layer-

intermediate layer-

-composed of elastic fibers and has slightly more mass

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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 mucosa- thinner 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 hyper- dysplasia.

• 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-Body-Theory 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

Vertical

Transverse

Anteriorposterior

Diaphragm

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Diaphragm/Abdominal Movement

Diaphragm

AbdominalWall

Inhalation Exhalation

Pelvis

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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 smaller2) diaphragm recoils back to the dome shape3) 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 diaphragm2) 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 on3) 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 Functions1) Valving for life:

1. Breathing2. Swallowing3. Pressure activities (sneezing, coughing, lifting etc.)

2) Valving for speech:1. Mechanics of voiceless sounds

-Whispering & voiceless consonants2. Mechanics of glottal vibration

-vibratory cycle3. 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

Muscular Glottis

CartilaginousGlottis

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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

• Arrows represent driving air pressure changes • Notice that the vocal folds are always in

transition

opening phase closing phase closed phase

open phase

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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

• Note how the vocal folds open from bottom to top & back to front.

Spread of glottal opening

Vertical Phase difference

Posterior

Anterior

Superior

Inferior

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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

• 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

Molecules

Compressedmolecular

traffic

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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 stiffness

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Mechanical Coupling Stiffness

• Upper & lower portions work together (coupled),

• Remember: The masses are the vocal folds,

• One of several muscular forces involved with phonation.

UpperMass

LowerMass

Upper Mass

Lower Mass

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Other muscular Forces• All provide resistance to airflow-

1) 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 control-

1) 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) modal2) falsetto3) 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.

LowPitch

HighPitch

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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 ofair, higher fundamental =greaterloudness,

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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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LoudnessSoft

Loud

volumevelocity

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!!!