Handout 4: Phonatory/laryngeal system Flashcards
vocal folds are
a valve in the airway at the level of the larynx (see Fig. 4.9 (5.8))
- a pair of structures that are each composed of epithelial tissue, mucus membrane, and muscle tissue
- primary role of the vocal folds in speech is to vibrate and thus generate the voice signal (one of the primary components of most speech sounds)
vocal folds role in nonspeech activities
protecting the airway (closing during swallowing, coughing) and assisting in strenuous lifting or pushing
the false vocal folds and epiglottis, located above the vocal folds also play an important role in …
closing and protecting the airway during swallowing but they have a very minor role in normal speech/voice
the vibraton of the vocal folds is a result of
the vocal folds continuously alternating between coming together (closed) and pushing apart (opened)
phonation
the vibration pattern of the vocal folds
the vibration of the vocal folds can be modified to…
accomplish the highly diverse sound qualities of the human voice (loud, soft, whisper, high, low, rough, smooth, hoarse, harsh, breathy, etc.)
the primary elements involved in vocal fold/voice modulations include ___ cartilages and ___ muscles
3, 5
thyroid cartilage
largest cartilage of the larynx (Figures 4.1-4.4 (5.1-5.4))
- formed by 2 plates that join at the front of the throat (Adam’s apple)
- the anterior end of the vocal folds attach to the inside of the thyroid cartilage
arytenoid cartilages
- a pair of small pyramid shaped cartilages that sit at the posterior edge or the thyroid cartilage and sit on the top of cricoid cartilage
- the posterior end of the vocal folds attach to the arytenoid cartilages
- thus the vocal folds stretch between the thyroid and arytenoids cartilages
cricoid cartilage
- a complete ring of cartilage that is just below the thyroid and arytenoids cartilages
- shaped like a signet ring
- the thyroid and arytenoids cartilages attach and form joints on the back of the cricoid
cricothyroid joint
allows for up and down tilting of the thyroid cartilage – plays a role in allowing for stretching of the vocal folds
cricoarytenoud joint
allows the arytenoids to rotate, rock and slide in a wide range of directions – this joint plays an important role in allowing for changes in the position of the vocal folds
which muscle opens the vocal folds (abduction)
posterior cricoarytenoud muscle - causes the arytenoids to rotate outwards and open folds
what two muscles close the vocal folds (adduction)
lateral cricoarytenoid
interarytenoid
lateral cricoayrtenoid causes the
arytenoids to rotate inwards and closes the vocal folds
the interarytenoid muscles causes the
arytenoids to be pulled together, pulling the VFs together
the two tensing and lengthening muscles of the VFs are
cricothyroid muscles
thyroarytenoud muscle
the cricothyroid muscle does what
pulls the thyrid cartilage forward and down - tenses/lengthens the VFs which raises pitch
thyroarytenoud muscle does what
can stiffen and tense the VFs - Chang vocal pitch and quality
myoelastic-aerodynamic theory of phonation is
- a widely accepted model of phonation that was proposed about 40 years ago
- describes voice production as a combination of muscle forces (myo), tissueelasticity (elastic), and air pressures and flows (aerodynamic)
medial compression
To initiate phonation the vocal folds are brought together (adducted) by continuously contracting the closing muscles (LCA and IA)
what happens once the VFs are closed
the subglottal pressure begins to build up quickly
when the subglottal pressure reaches 3-5 cmH2O what happens
forces vocal folds apart
rapid opening of the vocal folds causes
- rapid air flow thru which results in neg air pressure bw the folds
bernoulli effect
The rapid flow produces a negative air pressure to develop between the vocal folds and this causes the vocal folds to be pulled back together
the vocal folds get pulled back together bc of the bernoulli effect and because of
the elastic recoil of the vocal fold tissues and the continuous closing muscle contractions
how many layers of tissue in the vocal folds
5
what are the 5 layers of the vocal folds
1 - epithelium
2- superfifical layer of the lamina propria
3- intermediate layer of the lamina propria
4. deep layer of the lamina propria
5. thyroarytenoid muscle
what is the cover body model and what does it allow for?
stiffness of the cover layer and body layer can be adjusted somewhat independently by contracting diff muscles
this allows for a complex variety of voice qualities to be produced
complex layering of the VFs also causes the vocal folds to vibrate in a complex pattern…. observation of microdynamics of vibration reveal ….
both vertical waves and longitudinal waves during VF vibration
how is the vertical wave reflected?
vertical phase difference –> a time lag bw the opening and closing of the inferior and superior portions of the folds
how do the VFs open/close in the vertical dimension
open= bottom to top (inferior to superior)
close = bottom to top (inferior to superior)
the longitudinal wave is reflected by…
a time lag bw the opening and closing of the anterior and posterior portions of the VFs
how do the VFs open/close in the longitudinal direction
open = back to front (posterior to anterior)
close = front to back (anterior to posterior)
glottogram is a measurement of
vocal fold opening and closing
glottis
opening bw the vocal folds
what are the 3 ways to measure the glottis
high speed cinematography
video stroboscopy
electroglottography (EEG)
high speed cinematography
– laryngoscope placed at the back of the throat to view the vocal folds
– high speed film (4000 frames per second) allows for 20-40 pictures across each cycle of vocal fold vibration
– distance between the vocal folds or the area of the vocal fold opening can be measured
video stroboscopy
- takes pictures of vocal folds in synchrony with a flashing light
- only one picture is taken of each cycle of vibration
- if the flashing frequency is slightly slower than the fold vibration frequency the result is a slow motion movie of the vibration cycle
- distance between the folds, area of glottis, and vocal fold movement patterns can be obtained
electroglottography (EGG)
- two electrodes placed on either side of the neck (on the plates of the thyroid)
- as the folds open and close there is a change in the resistance and flow of electricity across the larynx/glottis
- the changes in electrical resistance can be shown as a continuous waveform (reflecting glottal opening)
- waveform measures such as the ratio of opening/closing time, closed phase duration, and slope of the closing phase are example of 3 types of measures that are often obtained from the EGG
- voice disorders are often associated with abnormal EGG measures
