Lecture 4 - 9/24 Flashcards
Primary Function of the Larynx
To protect the airway -Mechanically blocks foreign objects & food -Forcefully expels aspirated material
Secondary Function of the Larynx
-To produce voice
Brief and unspecific anatomy of Larynx and surroundings…
Larynx is suspended from hyoid bone Supports the tongue root Attaches to strap muscles –The suprahyoid & infrahyoid muscles – Elevate & lower larynx
KNOW THIS ANATOMY: (11)
Pharynx Tongue Jaw Epiglottis Hyoid bone Thyroid cartilage Cricoid cartilage Cricothyroid joint (control pitch) Arytenoid cartilages Cricoarytenoid joint (adduct & abduct VFs) Trachea
Innervation of Instrinsic Laryngeal Musculature
Vagus Nerve – Recurrent Laryngeal Branch -Thyroarytenoid muscle -Lateral cricoarytenoid muscle -Posterior cricoarytenoid -Interarytenoid muscles Vagus Nerve – Superior Laryngeal Branch -Cricothyroid muscle
Actions of Laryngeal Muscles
Adduct VFs -Thyroarytenoid muscle – Rotates arytenoid cartilages inward -Lateral cricoarytenoid muscle – Rotates arytenoid cartilages medially -Interarytenoid muscles – Approximates arytenoid cartilages Abduct VFs -Posterior cricoarytenoid muscle – Rotates the arytenoid cartilages laterally Shorten & Soften VFs -Thyroarytenoid muscle – Draws arytenoid cartilages toward thyroid to shorten the VFs Lengthen & Stiffen VFs -Cricothyroid muscle – Pulls thyroid & cricoid cartilages together to stiffen & elongate VFs
Extrinsic Musculature and Innervation
Elevators:
Trigeminal Nerve, CN V
-Digastric muscle, anterior belly
Facial Nerve, CN VII
- Digastric muscle, posterior belly
- Stylohyoid muscle
Glossopharyngeal Nerve, CN IX
-Stylopharyngeaus
Hypoglossal Nerve CN, XII
- Geniohyoid muscle
- Thyrohyoid muscle
Depressors:
Hypoglossal Nerve, C-1, C-2, & C-3
-Sternohyoid muscle
-Omohyoid muscle
-Sternothyoid muscle
-Cricothyroid muscle
Newborn Larynx
Newborn
-Larynx rides high in throat
-VFs are 2.5 -3 mm long
-Laryngeal cartilage is pliable
-Arytenoid cartilage including vocal process makes up ½ of length of VF
-The membranous portion of VFs is thick & uniform
-No evidence of vocal ligament
*The layered structure of lamina propria is not
developed
Development of Larynx and VT
Age 1-2 years
Immature thin vocal ligament develops
Age 3
Myelination of laryngeal nerves is complete
Age 4
Vocal tract lengthens as larynx descends
-Posterior 1/3 of tongue descends into pharynx
By age 5
-Larynx has adult configuration
By age 13 -15
-Vocal ligament has developed
-The three layers of lamina propria have developed
-Mutation of larynx occurs & fundamental frequency drops
in both males & females
-Mean male F0 drops from 226 Hz to 120 Hz
-Mean female F0 drops from 230 to 220 Hz
20-21 years of age
- Larynx reaches adult size
- Male VFs are 17-21 mm
- Female VFs are 11-15 mm
**Ossification of cartilage of larynx begins now & continues throughout entire life
Sex Specific Aging of Larynx
55+ Years Old
Males
- Thickening of deep layer of lamina propria
- Pitch elevates
Females
- Thinning of lamina propria
- Pitch lowers
- Increased roughness
- More vocal breakdowns
Aging of the Larynx (not sex specific)
80+ years old
Ossification of hyaline cartilage is almost complete
Heavier and less compliant
May have atrophy of the vocalis muscle
- Bowing of membranous portion of VFs
- Thinning of VF
May have stiffening of laryngeal joints
- Difficulty positioning arytenoid cartilage of VFs
- Glottal incompetency
- Increase in jitter & shimmer
Small bumps in the aryepiglottic fold
Two corniculate cartilages
Two cuneiform/arytenoid cartilages
Vocal process
Vocal Folds
Move quickly – Close glottis (to protect airway)
Delicate – Should not be pressed tightly together for prolonged periods
Myoelastic Aerodynamic Theory of Voice Production
Muller, 1843; van den Berg 1958
- Air passes through a narrow glottis
- Membranous portions of VFs are sucked together by Bernoulli effect
- Cartilaginous portion remains in phonation neutral position
- Air pressure builds below closed glottis
- Subglottal pressure exceeds 3-4 cm of H2O
- Membranous portions are blown apart
- Lateral excursion of membranous tissue
- Elasticity of membranous tissue is sufficient to snap VFs together & close glottis to create first glottal pulse (producing quiet phonation)
- Frequency of vibration is determined by length in relation to stiffness & mass of VF
Manner of Onset of Phonation
- Abrupt onset
- Full adduction of VFs (can lead to VF trauma) - Delayed onset of phonation – Voiceless initiation /hu/
- VFs partially abducted - Simultaneous onset of phonation – Voiced /mhm/
- VFs adducted to phonation neutral position - Abrupt Onset – Effortful Phonation
- Vocal folds hyperadducted
- Large excursions of VFs & high impact stress
Abrupt Onset of Phonation
- VFs fully adducted prior to onset of phonation
- Hold breath momentarily before starting phonation
- Feel strong burst at initiation
- Unnecessarily large excursions of VFs
- Possible phonotrauma
Aphonic manner of phonation
Delayed onset of phonation – Exhalation initiated prior to adduction of VFs
- Voiceless fricative
- Whisper
- Turbulent noise
Use in therapy – Decrease force of adduction of VFs & reduce effortful contact
Simultaneous Onset of Phonation
- Synchronized initiation of exhalation & adduction
- Gentle vibration with full closure after several cycles
- Effortless voicing
- Goal of therapy
- Synchronized adduction to phonation neutral position & initiation of exhalation
- Maintain a small space (~ 3 mm) between arytenoid cartilages
- Membranous portion vibrates in breath stream
COORDINATION: INITIATION OF PHONATION
Produce a sustained /a/ & focus on the sensations in your upper airway – Link these sensations to physiology
Can you produce /a/ with a breathy onset, simultaneous onset (gentle), & an abrupt initiation of phonation?
Multilayered Structure –
Cover, Transition, & Body
Cover – Flexible, medial edge of larynx – Generates mucosal wave
Squamous cell epithelium + gelatinous superficial layer of lamina propria
Transition – Intermediate + deep layer of lamina propria
Body – Stiffer thyroarytenoid muscle
Epithelium
Ciliated columnar epithelium
Durable squamous cell epithelium
Mucosal Wave
The cover is pliable, elastic, & not muscular, whereas body is stiffer & has active contractile properties that allow adjustment of stiffness
Primary striking zone midmembranous portion
Mucosal wave
- Occurs in & travels through the loose cover
- Generates harmonics & overtones in voice
- Produces rich vocal quality
Changes in cover alter the mucosal wave
Changes in cover alter the voice
Dynamic changes in prosody
Suprasegmental features
Modification of pitch, loudness, & timing
Mood
Intent of the message
Pitch and F0
Pitch = Perceptual assessment
Fundamental frequency (Fo) = Rate of VF vibration
Fo ≠ Pitch
Pitch Changes
Regulated by changes in VF length, stiffness, mass, & subglottal pressure
VF length is changed by contracting the cricothyroid muscles
VF is shortened and/or stiffened by contracting thyroarytenoid or vocalis muscle
Extrinsic muscles can raise or lower pitch
Intrinsic muscles can raise or lower pitch
(Does pitch match the patient’s age & gender?, Does the voice sound natural?, Focuses on resonance)
pSub
Subglottal pressure is controlled by changing the pattern of respiratory muscle activation & VF resistance
-You automatically change your subglottal pressure when you change your loudness.
The automatic coordination of subglottal pressure with sustained phonation depends on four things
- Volume of air in lungs
- Elastic recoil of chest wall
- Activation of external intercostal & abdominal muscles
- Coordination of respiration with medial compression (resistance) of VFs
Vocal Intensity
Subglottal pressure (Ps ) pressure below VFs
Measured by how far a column of water would be moved
Ps of 2-3 cm of H2O = Quiet voice ~40 dB
Ps of 5-7 cm of H2O = Conversational loudness ~60 dB
Ps of 15-20 cm of H2O = Loud voice ~100 dB
Average range of intensity of a sentence ~ 30 dB
Changes in Loudness
The duration of the closed phase of vibration increases with increased intensity
Sound pressure level increases when subglottic pressure increases
The medial compression of the VFs increases with loud sounds, and the larynx offers increased resistance to air flow
Result of excessive expiratory drive (subglottal pressure), medial compression, and stiffness of the VFs
Excessive loudness is a common risk factor/symptom
May lead to phonotrauma
Quieter phonation – Confidential voice
Voice therapy focuses on reducing phonatory effort & decreasing the transglottal pressure differential
Exploit the effect of back pressure/inertance to maintain low effort during speech
Quantifiable Measures: Fundamental frequency, Jitter, Shimmer, & Harmonics-to-noise Ratio
Fundamental frequency = Speed of vibration of VFs
Perturbation = Cycle-to-cycle variation in amplitude & frequency
Irregularity in VF vibration – Linked to laryngeal pathology, edema, stiffness, asynchrony, glottal closure
Noise in the signal = Ratio of harmonic sound to noise
Quantifiable Measures:
Pitch ≠ Fundamental Frequency
Mean fundamental frequency of infant distress cry
1-10 days = 384 Hz
4-6 weeks = 453 Hz
6-8 weeks = 495 Hz
6-9 months = 415 Hz
Mean fundamental frequency of sustained vowels
Mean male Fo = 130 Hz (range 85 & 155 Hz)
Mean female Fo = 220 Hz (165 to 255 Hz)
What does it mean if fundamental frequency is not within normal limits?
Pitch range
~ 35 semitones or 3 octaves
Acoustic Analysis
Algorithms – Automatically calculate fundamental frequency, intensity, perturbation, voice range profiles
Threats to Reliability
-Variations in equipment
-Variations in protocol
-Environment (e.g., ambient noise)
-Internal variability (time since last meal, hydration levels,
caffeine intake, emotional state)
-Variation within & between sessions
-Automatic calculation of measures
Titze & Lang, 1993:
Unfortunately, algorithms used to automatically calculate fundamental frequency, shimmer, & jitter are unreliable when fundamental frequency variability exceeds 6% per cycle
If desired, can further analyze voice sample with hand measurements
Objective Measures: Frequency Perturbation (Jitter)
Cycle-to-cycle variation in frequency
Collected on sustained vowels
Normative data supplied by instrument – Different instruments use slightly different formulas
Quantifiable Measures: Amplitude Perturbation (Shimmer)
Amplitude perturbation (shimmer)
Cycle-to-cycle variation in amplitude
Data is collected on sustained vowels
Normative data supplied with instrument – Different instruments use slightly different formulas
Quantifiable Measures: Harmonic-to-Noise Ratio
Sustained vowels
Compares harmonic energy to noise
Higher numbers = Greater periodic sound
Lower number = Greater aperiodic (noise) sound
Lower numbers = Greater roughness
