1178 Class 10 Laryngeal Physiology and Disorders PDF

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Laryngeal Physiology

1178 Class 10

Laryngeal Physiology • In speech production, the structures of the larynx modify airflow from the respiratory system: • Voicing: Adducting VFs • Voiceless Sounds: Abducted VFs

• Intonation: Changing VF vibration rate changes the perceived pitch of the speaker’s voice Vocal Folds = VFs

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Laryngeal Physiology Movement of the Arytenoid Cartilages

• Rocking of Arytenoids: Significant • Upward & Outward • Moves arytenoids father apart (abducts)

• Downward & Inward • Moves arytenoids closer together (adducts)

Laryngeal Physiology Movement of the Arytenoid Cartilages

• Gliding/Sliding of Arytenoids: Limited • Upward & Inward • Arytenoids approach one another (adduct)

• Downward & Outward • Arytenoids recede from one another (abduct)

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Laryngeal Physiology Movement of the Internal Larynx • Adduction of the VFs • Interarytenoid Muscles • Transverse pulls the arytenoids together • Upward & Inward gliding movement

Laryngeal Physiology Movement of the Internal Larynx • Adduction of the VFs • Interarytenoid Muscles • Oblique pulls one arytenoid toward the other • Downward & Inward rocking motion

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Laryngeal Physiology Movement of the Internal Larynx • Adduction of the VFs • Lateral cricoarytenoid (LCA) • Moves arytenoids toward midline • Downward & Inward rocking motion

Laryngeal Physiology Movement of the Internal Larynx • Abduction of the VFs • Posterior Cricoarytenoid (PCA) • Moves arytenoids away from midline • Upward & Outward rocking motion • Also active during physical exercise to permit movement of a greater volume of air

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Laryngeal Physiology Movement of the Internal Larynx • Lengthening/Stretching the VFs • Cricothyroid • Rocks thyroid cartilage forward • Decreases distance between the cricoid and thyroid cartilages • Elongates the VFs, increasing tension

• Only muscle in larynx whose primary function is lengthening

Laryngeal Physiology Movement of the Internal Larynx • Tensing the VFs • Thyroarytenoids • Isometric contractions of both TV and TM portions will tense medial and lateral aspects, respectively

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Laryngeal Physiology Movement of the Internal Larynx • Decreasing VF Length/Shortening • Thyroarytenoids • Isotonic Contraction of longitudinally oriented fibers • Shortens the muscle by reducing the distance between the thyroid and arytenoid cartilages (relaxes the VFs) • Forward pull on arytenoids, rocking them medially

Laryngeal Physiology Movement of the External Larynx • Positioning of the larynx • • • •

Up and back Up and forward Down and back Down and forward

• Decrease distance between hyoid and thyroid (stabilize)

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Laryngeal Physiology What do the movements lead to? • 5 Control Variables of Laryngeal Function: Laryngeal opposing pressure Laryngeal airway resistance Glottal size and configuration Stiffness of the vocal folds Effective mass of the vocal folds

Laryngeal Physiology Control Variables • Laryngeal Opposing Pressure (LOP) • Opposition provided by the larynx to translaryngeal pressure • Air pressure difference between the trachea and pharynx

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Laryngeal Physiology Control Variables • Laryngeal Opposing Pressure (LOP) • Variables • 1) *Muscular Pressure:* “squeezes” the larynx closed and holds the VFs together • 2) Surface tension between moist apposing surfaces • 3) Gravity: Holds down the VFs

Laryngeal Physiology Control Variables • Laryngeal Airway Resistance (LAR) • Opposition provided by the larynx to airflow through it • Main constriction site: level of vocal folds (secondary, ventricular folds)

• LAR is dependent on effective/sufficient LOP and expiratory airflow

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Laryngeal Physiology Control Variables • Glottal Size and Configuration • Main contributors: Abduction and Adduction of the VFs

Task Examples: A. __________________ B. __________________ C. __________________ D. __________________ E. __________________

Laryngeal Physiology Control Variables • Stiffness of Vocal Folds • Varies by location on the fold: • Stiffer near points of attachment • Increased tension is accomplished by: • Stretching VFs • Contraction of internal VF muscles

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Laryngeal Physiology Control Variables • Effective Mass of Vocal Folds • Mass of the VFs being vibrated • When fully adducted, all of the VFs are vibrating • When in a different glottal configuration, the effective mass is the portion that is adducted (vibrated)

Laryngeal Physiology Control Variables • Effective Mass of Vocal Folds • Full mass = Effective mass • VFs fully adducted, maximally elongated, free margins along the length

• Full Mass ≠ Effective mass: • Full mass partitioned by action that encumbers VFs at some point

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Sound Generation at the Level of the Larynx How are different sounds produced?

Laryngeal Physiology Sound Generation • Transient Sounds • Voiceless Stop-Plosive

• Production: • Full VF adduction • Subglottal air pressure builds up • Abrupt release

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Laryngeal Physiology Sound Generation • Sustained Utterance • Turbulence Noise Production • Production: • Some constriction of the glottis (medial movement of VFs) • Agitated air Æ frication

Laryngeal Physiology Sound Generation • Sustained Utterance • Voice Production • General Production: • Adducted posturing of glottis • Sufficient subglottal pressure • Sustained airflow thru VFs

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Laryngeal Physiology • Myoelastic-Aerodynamic Theory • Components: • Phonation Threshold Pressure (PTP) • Opening – Positive pressure • High concentration of air rushing Myo-elastic: properties of the out

• Closing – Bernoulli effect and elasticity

muscle and tissues Aerodynamic: motion of air around obstacles

Laryngeal Physiology • Myoelastic-Aerodynamic Theory • Bernoulli effect • Constriction of air through a tube causes faster airflow, but decreases pressure • Lower pressure in the passage (between the VFs)

• VFs are sucked together instead of being forced apart

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Laryngeal Physiology • Myoelastic-Aerodynamic Theory • Bernoulli effect

Supraglottal cavity

Supraglottal cavity VFs VFs

Subglottal cavity Subglottal cavity

Laryngeal Physiology • Myoelastic-Aerodynamic Theory • Sustained Voiced Utterance • VFs are appropriately postured • Subglottal pressure is built up below the VFs • Reach a Phonation Threshold Pressure Æ blows VFs apart

• Folds repeatedly open and close because of repeated pressure build-up, drop, etc.

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Laryngeal Physiology • Voice Production: • VFs do not open and close during phonation due to a separate muscle contraction for each opening/closing movement • VFs open and close “automatically” as long as: The folds are in the appropriate position and

There is sufficient buildup of pressure below them

Laryngeal Physiology • Vocal Fold Motion • Wavelike opening and closure • Both horizontal and vertical movements

https://www.youtube.com/watch?v=UsFtDdd3emE https://www.youtube.com/watch?v=9Tlpkdq8a8c

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Regulating Voice • Vocal Adjustments: • Fundamental Frequency (F 0) “Pitch” • Reflects the vibratory rate of the vocal folds. • Intensity “loudness” • Power from respiratory system, shape of glottis, shape of vocal tract, lip opening

• Quality • Perceptual characteristics

Vocal Folds and Acoustics • Basics on Sound Patterns: • Aperiodic/Quasiperiodic Sounds: • Do not have repeating pattern/waves • Noisy • Periodic Sounds: • Repeating pattern/waves • Intense, clear

Top Panel: periodic Bottom Panel: aperiodic https://www.phon.ucl.ac.uk/courses/spsci/iss/week2.php

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Vocal Folds and Acoustics • In normal voice production • VF Abduction = aperiodic sound • Aperiodic sounds are noisy • VF Adduction = periodic sound • Vibrating VFs affect the fundamental frequency (F0) of the resulting sound wave

Vocal Folds and Acoustics • Adduction results in vibration = periodic sound waves • VF vibration creates recurrent waveforms • Rate is defined as: cycles/second (Hertz, Hz)

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Vocal Folds and Acoustics • Vibration Rates: • Extremely slow VF vibration • ~60 vibrations per second, produces a low pitch • Extremely fast VF vibration • ~2000 vibrations per second, produces a very high pitch. • Note: Only the highest sopranos can attain these extremely high pitches

Averages by Sex: Men: Range: 90 - 500 Hz Mean = 115 Hz. Women: Range: 150 -1000 Hz Mean = 200 Hz

Vocal Folds and Acoustics • Factors that affect rate change: • VF Tension (stiffness): Major determinant of vibratory rate

• Increased tension = increased vibrations • VF Mass (thickness): • Increased mass = decreased vibration

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Vocal Folds and Acoustics • Factors that affect rate change: • VF Length: • Increased length = decreased vibration • Male VF are longer and vibrate less

• Volume of airflow • Increase in subglottal pressure = higher rate of vibration

Vocal Folds and Acoustics • Vocal Fold Mass • What is the effect of mass on the rate of vocal fold vibration?

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Vocal Fold Registers • Voice Registers • Reflect different modes of vibration resulting from different mechanical conditions • Differ in range of F0 and pattern of VF vibration

Vocal Fold Registers • Glottal Fry/Pulse: • Lowest F0 • VF’s close quickly, long closed phase of the cycle • VF’s are tightly closed (high LOP) • “Bubbles of air” escape, give voice “popcorn” quality.

• Least flexible • Low airflow • *Frequency < 100Hz

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Vocal Fold Registers • Modal register: • Widest range of F0 • Normal speaking voice

• Falsetto/Loft: • Highest F0 • Important role of tension • Often VFs do not close completely

Intensity Control • Sound pressure level (loudness) • Determined by glottal resistance (LAR) • Resistance = sufficient LOP/expiratory airflow • Increase resistance: • LOP Dominates at lower F0’s • Increased air pressure and prevent escape

• Expiratory airflow Dominates at higher F 0’s

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Vocal Quality Objective Parameters • Acoustic parameters (e.g., F0, Intensity) • Open quotient • Speed quotient

Subjective Parameters • Hoarse • Breathy • Strained/Strangled • Rough • Male versus Female

Vocal Quality Subjective Parameters Quality Perceptual Description

Breathiness Audible air escape in the voice

Tense/Strained /Pressed Sense of effort in production

Roughness Perceived cycleto-cycle variability in voice Uneven, “bumpy” sound

Physiologic Factors

Diminished or absent closed phase

Longer closed phase

Vocal folds vibrate, but in an irregular way

Reduced airflow Increased airflow

http://www.ntid.rit.edu/slpros/assessment/speechvoice/training/7

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Laryngeal Physiology Age, Sex and Laryngeal Function

Laryngeal Development • Laryngeal structure undergoes significant change between birth and adulthood • Relocation and remodeling process during development

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Laryngeal Development • Location: • Larynx begins high in neck and there is downward migration • Infant: • Lower edge of Cricoid sits opposite C2-3

• Adult: • Lower edge of Cricoid sits opposite C7

Laryngeal Development • Glottis: • Cartilaginous portion accounts for 60 - 75% of the VF length in children women) • Epiglottis, corniculated, cuneiform and arytenoid cartilages

Age and Laryngeal Function • Joints and Articular Surfaces: • Abrasion/erosion, ossification and deformation influence the movements • Cricoarytenoid: reduced movement leading to reduced vocal fold approximation

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Age and Laryngeal Function • Vocal Folds: • Nerve fiber loss • Muscle atrophy ( mass & strength) • Reduced elasticity, dehydration etc. • Changes to the lamina propria:

a.

• E.g., Fiber densities, fluid retention • Bowed or surface irregularities along free margins

Sex and Laryngeal Function • Dissimilarities between males and females in structure and function • Infancy/Early childhood • Relatively similar • Later childhood/puberty sex differences begin to emerge

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Sex and Laryngeal Function • Ossification: • Begins earlier in men (30s) than women (40s)

• Vocal Folds: • Males: • Lengthen • Full approximation

• Females: • Maintain relatively constant length • Often don’t have full approximation

Sex and Laryngeal Function • Fundamental Frequency (F0) : • Aging affects F 0 differently in males and females • Females: • Menopause and increased edema Æ lowering of F0

• Men: • Greater muscle atrophy, thinning of lamina propria, loss of mass Æ increase in F0

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Sex and Laryngeal Function Frequency by Age and Sex

Laryngeal Instrumentation and Disorders

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Instrumentation How do we see the vocal folds?

Problem: location

Instrumentation • Laryngoscopy (Endoscopy of the larynx) • Visualization of larynx via inserting a viewing device with a light source through the oral or nasal cavity • Rigid • Flexible

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Instrumentation • Laryngoscopy • Rigid • Inserted into the oral cavity along the surface of the tongue • Pros: • Excellent imaging • Cons: • Awkward/uncomfortable • Interferes with movement of pharyngeal-oral structures

Instrumentation • Laryngoscopy • Flexible • Inserted through the nasal cavity, over the upper surface of the velum and into the pharynx. • Pros: • Excellent visualization • Does not encumber the pharyngeal-oral structures

• Cons: • Can be uncomfortable

https://www.youtube.com/watch?v=GMS8dEtfis4

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Instrumentation • Laryngoscopic techniques can be coupled with videostroboscopic equipment • Mucosal waves are too fast for the human eye to appreciate • Strobe (brief flashes of light) “slows” this process by visualizing the mucosal wave across several cycles of vocalization

https://www.youtube.com/watch?v=xs7OObjlCbU

Helpful Study Note Disorders • For the exam: • You need to be able to discuss the difference between functional, organic and neurologic laryngeal disorders • Provide an example/s of each • You DO NOT need to be able to identify or define specific disorders

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Functional Laryngeal Disorders • Functional disorders: • Arise from the way in which we use our larynx to produce voice • E.g., • • • •

Nodules

nodules polyps Reinke’s edema hemorrhage Polyp

Functional Laryngeal Disorders Functional disorders:

Reinke’s edema – polypoid degeneration

Hemorrhage Reinke’s edema

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Organic Laryngeal Disorders • Organic disorders: • Directly related to a medical or “primary” etiology • Detectable physiological or structural change • E.g.,

Presbylaryngis

• malignant epithelial dysplasia • recurrent papilloma • presbyphonia/presbylaryng is

Neurologic Laryngeal Disorders • Neurologic disorders: • Occur when there is damage to the central or peripheral nervous system • E.g., • • • •

RLN or SLN Paralysis/Paresis Parkinson’s disease Multiple Sclerosis Amyotrophic Lateral Sclerosis

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