CMSD 5050 Lecture 9 Laryngeal Anatomy and Physiology 2024 PDF

2024-10-31 CHAPTER 4 LARYNGEAL ANATOMY AND PHYSIOLOGY Speech Science, November 1, 2024 Presentation composed by M. Kiefte, PhD Presented by Glen Nowell MSc., SLP-...

2024-10-31 CHAPTER 4 LARYNGEAL ANATOMY AND PHYSIOLOGY Speech Science, November 1, 2024 Presentation composed by M. Kiefte, PhD Presented by Glen Nowell MSc., SLP-Reg School of Communication Sciences and Disorders Dalhousie University 1 INTRODUCTION Larynx: principal structure for producing vibrating air stream Vocal folds: vibrating elements within the larynx that produce GLOTTAL TONE 2 BIOLOGICAL FUNCTION OF LARYNX Part of the respiratory system Protects the lower respiratory tract (keeps food, drink, reflux out) Valving mechanism Thoracic fixation Coughing Vocal folds abduct (spread widely apart) during normal breathing 3 1  2024-10-31 GLOTTAL SPECTRUM Generates sound ONLY when not active in biological functions Harmonics at integer multiples of Fo Can increase Fo at will, changing harmonic spacing Can increase intensity Spectral slope~ -12dB/8ve 4 bigger bubbles = louder sounds MUCOSAL WAVE Vocal folds adducted 5 MUCOSAL WAVE Subglottal pressure (Psub) increases 6 2  2024-10-31 MUCOSAL WAVE Vocal folds blown apart 7 MUCOSAL WAVE Puff of air is released 8 MUCOSAL WAVE Subglottal air pressure decreases 9 3  2024-10-31 MUCOSAL WAVE tissue elasticity and lower air pressure allows vocal folds to snap back 10 MUCOSAL WAVE Process repeats Second verse, same as the first 11 COMPARISON OF STROBE AND HIGH SPEED KayPENTAX 12 4  2024-10-31 stabilises larynx HYOID BONE Supportive structure for tongue root Inferior attachment for most tongue muscles Superior attachment for some extrinsic laryngeal muscles Larynx suspended from hyoid by the thyrohyoid membrane (AKA hyothyroid membrane) 13 HYOID BONE Only bone not connected to any other bone, suspended in a lattice of muscles Greater horn: sternohyoid, geniohyoid, mylohyoid, hyoglossus, omohyoid, thyrohyoid, constrictor pharyngeus medius, chondroglossus, genioglossus Lesser horn connects to stylohyoid and digastric (anterior and posterior bellies) 14 CARTILAGENOUS vocal folds attached to thyroid cartilage FRAMEWORK OF LARYNX muscles named after cartilages Thyroid: largest laryngeal cartilage, Hyaline. Cricoid: signet ring, only complete tracheal circoid cartilage gradually turns to bone ring. Hyaline. Epiglottis: elastic. Leaf shaped. Arytenoids: pyramid shaped. Elastic. Corniculates: like penguin heads. Elastic. Cuneiform: cylindrical stiffeners in the aryepiglottic folds. Elastic. Hyaline ossifies with age. 15 5  2024-10-31 THYROID CARTILAGE laminae 2 quadrilateral plates laryngeal prominence Adam’s apple thyroid notch prominent V-shaped notch above laryngeal prominence anterior commissure inner surface below notch where vocal folds attach superior horns attached to greater horns of hyoid inferior horns shorter & articulate with cricoid Horns are also called CORNU 16 THYROID Estrogenic puberty Androgenic puberty 17 CRICOID CARTILAGE lower framework of larynx attaches to thyroid by cricothyroid membrane attaches to first tracheal ring by cricotracheal membrane articulates with inferior horns of thyroid arch anterior band (quadrate) lamina posterior plate 18 6  2024-10-31 ARYTENOID CARTILAGES muscular process-- projection that articulates with cricoid point of attachment for important laryngeal musculature vocal process-- anterior projection near base in which vocal ligament inserts corniculate cartilages-- perch on the arytenoids 19 EPIGLOTTIS ANATOMY lies behind hyoid & tongue root attached to thyroid just below notch and hyoid by ligaments (thyroepiglottic and hyoepiglottic ligaments) easily seen during oral examination of children 20 ILLUSTRATION OF LARYNGEAL CARTILAGES 21 7  2024-10-31 LARYNGEAL CARTILAGES 22 EPIGLOTTIS ANATOMY aryepiglottic folds extend from sides of epiglottis to apices of arytenoids form entrance (aditus) to larynx contract to pull epiglottis backwards vallecula wedge-shaped space between tongue and epiglottis (plural is valleculae) 23 EPIGLOTTIS REAR VIEW 24 8  2024-10-31 EPIGLOTTIS FUNCTION Helps prevent food from entering larynx (drape cloth over larynx) Contributes very little to speech production (unless you’re Shaggy) Not a vital organ in humans 25 CUNEIFORM CARTILAGES Small cylindrical shape cartilages embedded within aryepiglottic cartilages Appear as swellings when viewed from above Vestigial (may be absent in some) Support, stiffen aryepiglottic folds to maintain opening 26 false vocal fold: should not be vibrating when speaking GLOTTIS: ABDUCTED 27 9  2024-10-31 GLOTTIS: ADDUCTED 28 LARYNGEAL JOINTS 2 pairs of joints Cricoarytenoid cricothyroid All vocal fold adjustments are mediated through these 29 CRICOARYTENOID JOINT 2 motions: Rocking Limited Gliding 30 10  2024-10-31 CRICOTHYROID JOINT Primary action is rotational Places vocal folds under increased tension (raises pitch) 31 EXTRINSIC LARYNGEAL MEMBRANES thyrohoid membrane suspends larynx from hyoid medial thyrohyoid ligament lateral thyrohyoid ligaments cricothyroid membrane connects thyroid and cricoid anteriorly cricotracheal membrane connects lower border of cricoid to upper border of 1st tracheal ring 32 LATERAL VIEW OF THE LARYNX 33 11  2024-10-31 CAVITIES OF THE LARYNX Laryngeal vestibule: above the vestibular/ventricular folds. Epiglottis in front, aryepiglottic folds along sides, arytenoids behind. Aditus: superior entrance to laryngeal cavity. Between the vestibular/ventricular folds and vocal folds (where the ventricles live). Supraglottal region: above true vocal folds Subglottal region: below true vocal folds 34 VOCAL FOLDS Composed of a bundle of muscle tissue (thyroarytenoid) and vocal ligament which is continuous with the conus elasticus Glottis: variable opening between vocal folds Vocalis: medial portion of thyroarytenoid flanking vocal ligament 35 VOCAL FOLDS Membranous portion: anterior 2/3 (attached to thyroid cartilage) Cartilaginous portion: posterior 1/3 (contiguous with arytenoid cartilage) When whispering, cartilaginous portion is open and membranous portion closed 36 12  2024-10-31 VIBRATING ANTERIOR 2/3 KayPentax 37 HISTOLOGY OF VOCAL body of vocal fold: muscle FOLD Epithelium: outer capsule that maintains shape Superficial layer of laminal propria: elastic gelatinous mass Intermediate layer of lamina propria: like soft rubber bands 38 HISTOLOGY OF VOCAL FOLD Deep layer of lamina propria: like cotton thread Thyroarytenoid muscle: like stiff rubber bands 39 13  2024-10-31 HISTOLOGY OF VOCAL FOLD 40 PHYSIOLOGY OF VOCAL FOLD COVER-BODY MODEL Three layers: 1. Cover: epithelium and superficial layer of lamina propria Highly compliant 2. Transition: intermediate and deep layers of lamina propria Stiffer Vocal Ligament 3. Body: thyroarytenoid muscle (vocalis) Outer four layers are controlled passively Thyroarytenoid muscle: both actively and passively controlled 41 FALSE VOCAL (VENTRICULAR) FOLDS Above the True Vocal Folds Attach to thyroid and arytenoid cartilages Close during swallow False glottis: space between ventricular folds Wider than glottis 42 14  2024-10-31 NORMAL LARYNX 43 SUPRAGLOTTAL REGION Ventricle: cavity between ventricular (false) folds and true vocal folds Goblet cells secrete oil- based lubrication for vocal folds 44 MUSCLES OF THE LARYNX Extrinsic: have attachments in larynx and outside larynx Support and position the larynx Also called Strap Muscles Intrinsic: have both attachment points within the larynx Have predominant control of phonation 45 15  2024-10-31 EXTRINSIC MUSCLES Sternothyroid: anterior neck muscle, connects sternum and first costal cartilage to thyroid cartilage Thyrohyoid: anterior neck muscle, connects thyroid laminae to greater horn of hyoid bone 46 important for swallowing & voice SUPRAHYOID MUSCLES Digastric: 2 fleshy bellies; mandible & mastoid process → hyoid Stylohyoid: styloid process → hyoid. mylohyoid thin sheet of muscle forming mouth floor. 47 SUPRAHYOID MUSCLES CONT’D Geniohyoid: chin → hyoid. 48 16  2024-10-31 SUPRAHYOIDS 49 INFRAHYOID MUSCLES Sternohyoid: flat anterior neck muscle; sternoclavicular joint → hyoid Omohyoid: long, narrow, 2- bellied muscle; scapula → hyoid 50 SUPRAHYOIDS, INFRAHYOIDS 51 17  2024-10-31 INTRINSIC MUSCLES four categories according to effects on glottis: 1 abductor open glottis 2 adductor close glottis 3 tensor elongate & tighten vocal folds 4 relaxer shorten vocal folds 52 INTRINSIC MUSCLES two main types of internal laryngeal adjustments: 1 medial compression force with which vocal folds are brought together 2 longitudinal tension degree of stretching 53 PCA ONLY ABDUCTORY INTRINSIC INTRINSIC MUSCLES thyroarytenoid (TA) primary muscular mass of vocal folds from anterior commissure to arytenoids (relaxer) posterior cricoarytenoid (PCA) posterior surface of larynx (abductor) lateral cricoarytenoid (LCA) fibers course up & back (adductor) interarytenoids (IA) course from one arytenoid to the other (adductor: bring arytenoids together) transverse & oblique cricothyroid (CT) glottal tensor antagonist to thyroarytenoid vocal pitch changer pars recta & pars oblique 54 18  2024-10-31 LATERAL CRICOARYTENOID 55 PCA & IA 56 POSTERIOR CRICOARYTENOID ACTION 57 19  2024-10-31 LARYNGEAL CARTILAGES: ABDUCTED 58 LARYNGEAL CARTILAGES: ADDUCTED 59 CRICOTHYROID MUSCLE 60 20  2024-10-31 SUMMARY OF INTRINSIC MUSCLE ACTIVITY 61 LARYNGEAL PHYSIOLOGY & MECHANICS OF PHONATION pitch depends on: 1 frequency of vocal fold vibration 2 mode (pattern) of vocal fold vibration factors that influence rate of vocal fold vibration: 1 longitudinal tension (active) 2 tissue elasticity (passive/active) 3 vocal fold length (passive/active) 4 vocal fold mass (passive) 62 AIRFLOW AND PRESSURE pressure behind constriction greater than pressure at constriction velocity of a fluid is inversely proportional to the cross-sectional area A1v1 = A2v2 same volume of fluid passes a given point over a given time airflow increases at constriction 63 21  2024-10-31 AIRFLOW AND PRESSURE Bernoulli principle Pressure drops when speed of fluid increases. airflow increases at point of constriction conservation of energy: kinetic energy ↑; pressure ↓ vocal folds sucked toward one another 64 VOCAL FOLD VIBRATION vocal folds vibrate before they meet two factors contribute to vocal fold adduction in phonation: 1 vocal fold elasticity 2 Bernoulli principle 65 MYOELASTIC-AERODYNAMIC THEORY vocal fold vibration depends on physical laws physical properties regulated by intrinsic muscles three forces: 1 elasticity of vocal folds (myoelastic: adducting) 2 Bernoulli principle (aerodynamic: adducting) 3 subglottal pressure (aerodynamic: abducting) most widely accepted theory 66 22  2024-10-31 PHONATION THRESHOLD PRESSURE transglottal pressure differential between subglottal and supraglottal pressure phonation threshold pressure (PTP) minimum amount of transglottal pressure to set vocal folds in vibration 3–6 cm H2O (300–600 Pa, respectively) for normal speech up to 50 cm H2O for yelling 67 LARYNGEAL MODELS Mathematical models allow systematic study of vocal fold vibration & acoustic output. one-mass model single mass that moves to & from midline 68 LARYNGEAL MODELS three-mass model: can also account for vertical phase difference or mucosal wave 69 23  2024-10-31 MODE OF VOCAL FOLD VIBRATION posterior VF typically opens first & closes last—longitudinal phase difference vibration mostly horizontal vertical displacement increases with increased intensity 70 MODE OF VF VIBRATION vertical phase difference lower edges blown apart first and close first vibration of superior and inferior margins are out of phase 71 PITCH-CHANGING MECHANISM Pitch range during conversational speech ≈ 2 oct. fundamental frequency average rate of VF vibration. cis males: ≈ 120Hz cis females: ≈ 220Hz children: ≈ 300Hz cis male larynx grows much faster than cis female during puberty due to differences in sex hormones natural level/optimum pitch level most suitable pitch level for an individual determined by anatomy/physiology cis males: 15–20 mm cis females: 9–13 mm 72 24  2024-10-31 PITCH-RAISING MECHANISM as pitch increases: 1 length increases 2 cross-sectional area decreases Increased VF tension may be sole cause of increased pitch. 73 PITCH-RAISING MECHANISM Intrinsic muscles for increased tension—primarily cricothyroid. Increased vocal-fold tension requires increased subglottal pressure. 74 VOICE REGISTERS Register: Pitch range similar in production & quality—manner of vocal-fold vibration chest midrange of pitches modal register falsetto extreme upper portion of pitch range. vocal folds come together only at edges high longitudinal tension loft voice pulse popping, creaky sound produced by phonating quietly at lowest possible pitch. glottal fry/vocal fry/creaky voice often at ends of sentences very long closed phase 75 25  2024-10-31 PARAMETERS OF VOICE PRODUCTION maximum frequency range usually 2.5–3 oct. mean rate of vocal fold vibration habitual pitch, speaking Fo maximum phonation time air cost 100–200 ml/s. Sustained phonation for 15–25 s. minimum-maximum amplitude at least 20–30 dB 76 PARAMETERS OF VOICE PRODUCTION Jitter: between-cycle differences in glottal period. periodicity of vocal fold vibration frequency perturbation differences of more than 1% sound rough/hoarse Shimmer: between-cycle differences in glottal amplitude amplitude perturbation Noise: aperiodic sound associated with roughness 77 VOCAL QUALITY dysphonia deviant in quality, pitch, and/or loudness. breathy poor approximation of vocal folds generates noise low subglottal pressure → low intensity high air cost example of hypoadduction rough/hoarse aperiodic vocal fold vibration. glottal attack excessive medial compression & tension 78 26  2024-10-31 CHANGES OVER LIFESPAN Presbyphonia age-related changes in voice quality Muscle atrophy of vocal folds Loss of collagen from vocal ligament Breathiness, hoarseness from reduced VF mass (bowed vocal folds) Increase in Fo for cis males, decrease in Fo for cis females 79 REFERENCES Kay PENTAX video files comparing high speed to stroboscopy Speech Science: An Integrated Approach to Theory and Clinical Practice (4 th ed.). Carole T. Ferrand (2018). Pearson publication. 80 27