PHONATION - DR NITIN ANIYAN THOMAS (NATS)

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PHONATION AND ITS MECHANISM
HOW PHONATION WORKS
HOW SOUND IS PRODUCED
PHONATION DIORDERS
DIFFERENT CONDITIONS AFFECTING PHONATION
VOCAL FOLDS AND ITS ANATOMY AND FUNCTIONING

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  • PHONATION - DR NITIN ANIYAN THOMAS (NATS)

    1. 1. PHONATIO N
    2. 2. Process by which vocal folds produce certain sounds through periodic vibration .
    3. 3. OSCILLATION Repeated back & forth movement VOCAL CORD OSCILLATION Flow induced oscillation Steady flow of air Pass by a wall / surface Surface vibrates
    4. 4. VOCAL FOLDS • • • • • • • • • • Housed with protective cartilage of larynx Vocal folds very small {18mm - women ; 23mm -men} Part of fold responsible for sound production is further smaller During phonation – only anterior part of fold is free to vibrate Appearance : Pearly white bands looks like “ V ” on rest During phonation they close together at Posterior part Bottom of this V points to front of neck and Adams apple Space b/w vocal folds GLOTTIS which opens for respiration & closes for phonation above the folds pink-coloured ventricular folds , also k/a false vocal folds
    5. 5. A curved structure k/a epiglottis arise from the closed point of the vocal folds cover airway during swallowing and direct food into the esophagus toward the stomach
    6. 6. VOCAL FOLD STRUCTURE Vocal folds – body & cover Cover - lined by Stratified Squamous Epith Aka Mucosa of the vocal folds Below vocal folds – lined by Ciliated Columnar Epith. Body : Has thyroaretynoid muscle (Origin : Thyroid cartilage & Insetion : Arytenoid cartilage) A transitional layer b/w muscle & epithelial cover LAMINIA PROPRIA Has 3 layers
    7. 7. Superficial Outer most layer Intermediate Middle layer Superficial Layer Joins epith. Via basement memb Thinnest layer Lowest viscosity Intermediate Layer More wider More viscous Vocal ligament passess through this layer Deep Inner layer
    8. 8. Deep Layer Densest & most viscous Transition from vocal fold cover to body is completed Lamina propria compared : To a 3-layered gelatin dessert in which Superficial layer - incompletely set Intermediate layer - normal gelatin deep layer more - resembles a gummi
    9. 9. This pattern helps the cover to slide gently in position relative to body oscillation facilitated In healthy vocal folds . using high-speed or stroboscopic cameras ,surface of fold appears to ripple in a wave like motion k/a MUCOSAL WAVE Voice disorders impair phonation: By impeding mucosal wave formation ( Eg: the hoarseness or loss of voice) from  laryngitis (laryngeal inflammation) – d/t vocal fold swelling - makes the cover adhere tightly to body. The folds lose their suppleness and become too rigid to oscillate
    10. 10. THEORIES OF VOCAL OSCILLATION FOLD Muscular activities alone are not able to open and close the glottis rapidly enough for sound  Production  To sing vocal folds must open and close at a much faster rate up to 1400 times / sec No muscles can do this
    11. 11. MYOELASTIC AERO DYNAMIC THEORY Vocal cord oscillation Muscular + Aerodynamic process Aerodynamic Process Demonstrated by Daniel Bernoulli (18 century) Fluid Dynamic If Vol. of fluid / Gas Pass confined area inversely propotional to Constant energy Expressed as pressure & flow
    12. 12. Eg : Water passing through a pipe VOCAL FOLD OSCILLN. & ROLE OF BERNOULLI EFFECT Laryngeal mus. Close vocal folds Air pr. ses` beneath Air flows thru glottis opens glottis from bottom to top with velocity & press. until air escapes Glottis closes d/t air flow pr. Process repeats
    13. 13. The time of Open : close ratio of vocal folds Measuring the images by High speed or Stroboscopic motion picture Also measured by a painless , non invasive Electroglottograph (EGG) { Elecrodes placed on either side of neck - radio freq waves passed via larynx - Glottic opening & closing induce changes in electrical resistance - measured & plotted by EGG } RATE OF GLOTTIC OPENING & CLOSING OPEN : CLOSED RATIO
    14. 14. NORMAL PHONATION BREATHY PHONATION { Vocal Cords are not fully closed on Stroboscopy & EGG }
    15. 15. THE ONE MASS MODEL THEORY Myoelastic-Aerodynamic theory was improved by adding the contribution of the vocal tract & its impact on airflow In the physical world objects experience inertia which is resistance to starting & stopping movement vocal folds and the air moving through the vocal tract also are subject to this natural law In A-M theory glottis initially closed by muscles in larynx
    16. 16. Subglottal air pr. Till it overcomes muscular & tissue resistance & opens glottis Air pr. through glottis (Bernoulli) & elasticity / Inertia of vocal folds Brings glottis back together flow of air Becoz of inertia, air above glottis cont. its 4ward motion through the glottis
    17. 17. Combined forces of elastic recoil of the folds + pressure drop through the glottis + low pressure region above the glottis completes cycle ,closing the glottis Asymmetry of air pr. below & above glottis allows Vocal fold oscillation to continue for as many times per second depending on the pitch that is spoken or sung
    18. 18. THREE MASS MODEL Vocal folds consider as 3 interconnected masses First & largest mass - body of the vocal fold ( thyroarytenoid muscle) Two smaller masses - upper and lower portions of the cover (lamina propria and epithelium) Glottis opens and closes asymmetrically with vertical phase difference from bottom to top. Air pressure also is asymmetrical When glottis is convergent (Bottoms of 2 folds r farther apart) Divergent (tops of 2 folds r farther apart) Increasing decreasing Asymmetry of air pressure + impact of pr. changes above glottis caused by Inertia  sufficient to sustain vocal fold oscillation
    19. 19. NEUROCHRONAXIC THEORY Raoul Husson (1901-67) French scientist &voice enthusiast believed that nerve impulses from brain sole cause of vocal fold vibration & that airflow only is needed to carry the sound outside the body
    20. 20. DEGREE OF PHONATION VOICELESSNESS - NO VIBRATION
    21. 21.  BREATHY VOICE VOCAL CORDS VIBRATE WHILE THEY ARE FURTHER APART
    22. 22. MODAL VOICE Max. Vibration o STIFF VOICE Glottal opening is narrower o
    23. 23.  Faucalized voice (hollow or yawny voice) Laryngeal cavity is expanded
    24. 24. WHISPER Greater adduction than in breathy voice  HARSH VOICE Ventricular or pressed voice `
    25. 25. PHONATION DISORDERS • MYAESTHENIA GRAVIS auto-immune disease affect the nerve-muscle interface causing general muscle weakness. HOARSENESS VOICE FATIGUE DIFFICULTY IN CONTROLLING PITCH OF VOICE T/T: Anti cholinesterase – restore muscle strength & tendency towards fatigue
    26. 26. • PARKINSONS DISEASE Degenerative disorder of the CNS Motor symptoms of Parkinson's disease result from death of dopamine-generating cells a region of the midbrain low volume voice with a "monotone“ (expressionless) quality T/t : Levadopa and dopamine agonists
    27. 27. • VOCAL HYPER FUNCTION It’s the functional abuse of the vocal mechanism. e.g : excessively loud speech. - Can cause nodule
    28. 28. MCC : T/T : Speech Therapy
    29. 29. VOCAL FOLD PARALYSIS Inability of 1 or both vocal folds (vocal cords) to move d/t damage to nerves going to vocal cords d/t damage to the brain itself How does it affect voice? Abductor: phonation in inspiration and exhalation Adductor: no phonation
    30. 30. T/t : Voice therapy: To make the working vocal cord "compensate" for the vocal cord paralysis.. Surgical: Almost IMMEDIATE improvement of all symptoms seen, especially vocal quality and strength.
    31. 31. VOCAL CORD POLYP Non cancerous growths on the vocal cords that affect voice. Sometimes caused by vocal abuse T/t : Small polyps can be treated with Voice therapy, but typically they are surgically removed
    32. 32. VOCAL FOLD CANCER T/t depends on the site and extent of involvement + consideration of other health issues the person may have • Treatment options o Surgery o Laser surgery o Radiation therapy o Chemotherapy o Combination therapy
    33. 33. Eg of a very early cancer of the vocal folds.If these lesions are detected early, they can be treated with either radiation or surgery, with a cure rate approaching 96%.

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