Sarah Boucher McCoy Ch. 8

What is the total at rest length of the vocal folds for women? For men?

18 milimeters for women and 23 milimeters for men

What is the average length of the vibrating portion of the vocal folds?   

The anterior porition (the section that vibrates) is about 12-15 milimeters long 

Why do we call them vocal folds instead of vocal cords?

Because it more accurately describes what they look like: they are small folds of tissue.

What are the vocal folds?

two pearly white bands that look like the letter V at rest, but come together during phonation. 

What do the vocal folds look like when viewed from above?

a V

What is the thin layer of skin cells on the VFs called? What do these 3 terms mean?

Stratified squamous epithelium

Epithelium: skin cells

Stratified: layered

Squamous: interlocking

This area has another name.  What is it and why is it called this?

Mucosa, because it is constantly bathed in mucus

What is unique about this layer of skin (covering the VFs) as opposed to the rest of the epithelium of the vocal tract?
it is covered with microscopic hairs that transport mucus up the airway for disposal via the esophagus and stomach

What makes up the body of the vocal folds?

The thyroarytenoid

What is the transitional layer called?  Describe it.

The lamina propria lies between the TA and the epithelial cover and it has 3 regions the deep, intermediate and superficial lamina propria. The superficial lamina propria is the thinnest and has the lowest fluid density, the intermediate  is wider and more dense, and the deep is the biggest and most dense.

How is the structure of the vocal folds like both the back and the palm of your hand?

The cover is like the skin on the back of your hand and the lamina propria is the shock absorber like the palm.

Describe the steps of a single cycle of vibration according to the Myoelastic-Aerodynamic Model.

1. The vocal folds are gently closed by muscular forces

2. Air pressure increases beneath the glottis

3. The increase of air pressure opens the glottis

4. The glottis continues to open from bottom to top, until air escapes

5. As the air flows through the glottis, the velocity increases and the pressure decreases.

6. Elasticity of the vocal folds causes them to move towards closure again.

7. The glottis closes from top to bottom

8. Once the glottis is fully closed the cycle starts again.

What is vertical phase difference?  Why is this important to vocal sound?

Vertical phase difference is the time lapse between the opening and closing of the different portions of the vocal folds. It is important because independent movement of the portions of the vocal folds create mucosal waves.

Are aerodynamic factors sufficient to maintain vocal fold oscillation?

no

Describe the steps of VF oscillation according to the one-mass model.

1. The glottis is closed by the muscles of the larynx

2. Subglottal pressure opens the glottis

3. Reduced air pressure increases until it overcomes the muscular and tissue resistance and opens the glottis.

4. Because of inertia, air above the glottis continues its forward motion in spite of reduced flow through the glottis, producing an area of low air pressure immediately above the glottis.

5. The combined forces of elastic recoil, the pressure drop through the glottis, and low pressure above the glottis complete the cycle, closing the glottis.

6. Asymmetry of air pressure below and above the glottis allows vocal fold oscillation to continue.

Describe the improvements in understanding VF oscillation because of the 3-mass model.

The glottis opens and closes asymmetrically with vertical phase difference from bottom to top. Air pressure is also asymmetrical, increasing when the glottis is convergent.

What is the neurochronaxic theory?  If it valid?

It is Raoul Husson's theory that airflow is only needed to carry the sound outside the body, it is not valid.

Name the 5 cartilages that form the basic laryngeal framework.

Thyroid, Cricoid, Two arytenoids and the epiglottis.

Name and describe the membranes and ligaments found within the larynx.

Thyrohyoid membrane- located between the thyroid cartilage and the hyoid bone, links the two structures, provides a seal that prevents excess movement. 

cricothyroid membrane and ligament - between the thyroid and cricoid cartilage, link the structures and seals for excess movement

Conus elasticus - lines the inside of the cricoid cartilage, strengthens the underside of the vocal folds and seals them to the airway below

Describe the aryepiglottic fold.  What is its alternate name? What is its function?

The aryepiglottic fold is found at the top of the larynx. It is also called the laryngeal collar or the epilarynx. It pulls the epiglottis down to cover the airway for swallowing. 

What is the purpose of the vocal ligament?

to add strength to the medial edges of the vocal folds and to limit the extent that it can be stretched.

What is the function of the aryepiglottic and the thyroepiglottic muscles for singing?

They tilt the epiglottis slightly backward while simultaneously narrowing the laryngeal oulet at the epilarynx. (Enhancing the strength of the singer's formant. 

What is phonation threshold pressure (PTP)?

The pressure required to overcome the resistance of glottal adduction and initiate vocal fold oscillation)

What are the 3 principle types of vocal onset? Describe how they differ in terms of the sequence of adduction and airflow.

Glottal - Strong adduction proceeds breath energy

Aspirate - Breath flow starts and vocal folds slowly adduct

Balanced  - adduction and airflow begin at precisely the same instant

What is flow phonation?

a perfect union of airflow and adductory tension that creates a well balanced tone

What happens if we increase breath pressure with constant adductory tension?

 the sound will get slightly louder, but will also rise in pitch and possibly become aspirate

What happens is you increase glottal resistance at the same time as you increase breath pressure?

the amplitude will increase, and the airflow will be more well utilized

As amplitude increases, how does this affect the glottis? What happens to help this situation?

As the amplitude increases the glottis must work harder to resist subglottal pressure. In order to do this there must be increased contraction in the adductor muscles and contraction of the TA.

How do we increase vocal fold thickness, and what affect does this have on the sound?

The TA contract in isometric antagonism with the CT muscles. This amplifies the sound.

What is the typical dynamic range for dramatic voices?  What was maximum amplitude for these singers?

dynamic range of 60-64 db and an maximum amplitude of 120 db. 

How does the dynamic range and maximum amplitude of lighter voiced singers compare?
lighter voices have a similar dynamic range up but there amplitude is lower.
 

How do pitch and amplitude relate to each other?

higher pitches have higher amplitude
 
How is the time that the glottis remains open impacted by adduction and pressure changes?
as adduction and pressure increases the length of time the glottis stays open decreases
 

What is the estimated times of the various phases in a quiet tone vs a louder tone?
quiet - opening phase of 50%, closing phase of 37% and closed for 13%
louder - opening phase 33%, closing phase 37% and closed for 30%

What is the open quotient?
the time the glottis is open during each cycle
 

How does the open quotient relate to amplitude?
amplitude increases as the open quotient falls

Why is it wrong to just blow harder to get louder?
it makes people sing sharp
 

In very general terms, what must the vocal folds do to change pitch?
the vocal folds must be elongated for pitch to ascend and shortened for pitch to descend.

How does the body/cover model affect pitch change?
at lower frequencies the whole vocal folds oscillate as pitch ascends the body and the cover are more independent

How do pitch and intensity overlap in terms of vocal fold function?
higher pitches require longer, stiffer, and narrower vocal folds, but louder sounds require thicker vocal folds
 

How do the CT and TA work together to control pitch and amplitude?
the CT muscles pull the folds to the appropriate tension and the TA muscles counter with tension for amplitude
 

Describe how variations in air pressure have different impacts on low vs. high frequencies.
higher pitches tend to require more subglottal pressure. 

Describe the inferior pharyngeal constrictor muscles connection to the larynx. Describe its function.
attaches to either side of the thyroid cartilage and wraps around the vocal tract  and the base of the esophagus. contraction narrows the pharynx and elevates the larynx
 

What is ossification?
the gradual transformation of cartilage to bone
 

What is the downside of the flexibility of the thyroid cartilage in young people.
vocal instability and unpredictability
 

Describe the actions of swallowing
the larynx ascends, the epiglottis folds over the airway, the soft palate is lifted closing the nasal port, tongue elevates and contracts, the walls of the pharynx constrict
 

Describe the pharyngeal constrictor muscles.
superior constrictor: wraps around the top of the vocal tract and attaches to the skull and mandible
middle constrictor: attaches to the hyoid bone and the stylohyoid ligament
inferior constrictor: attaches to the thyroid laminae  and cricoid cartilage
 

What doe gola aperta mean?
the sensation of an open throat
 

How do we open the throat? 
all tension is released from the three sets of the constrictor muscles, "passive relaxation"
 

What are the two ways in which laryngeal elevation can occur?
lifting directly through an attachment to the thyroid or cricoid cartilage or it is lifted indirectly through the hyoid bone
 

Which structures is the hyoid connected to?
the larynx, tongue, and jaw

Besides the inferior pharyngeal constrictor, what is the other true laryngeal elevator? Describe its function.

thyrohyoid: lifts the larynx and partially closes the gap between the thyroid cartilage and hyoid.

Which muscles are indirect laryngeal elevators?
digastric, stylohyoid, mylohyoid, hyoglossus
 

If the muscles that close the jaw (masseter, temporalis, medial pterygoid) fail to release when the jaw is opened, what if the effect of the contraction of the anterior belly of the digastric?
the jaw becomes rigidly fixed in place, the digastric lowers the jaw but also elevates the larynx
 

Which muscles can both depress the jaw and raise the larynx?

stylohyoid and the mylohyoid
 
Which muscles are laryngeal depressors?
sternothyroid, sternohyoid, omohyoid
 

What is the ideal laryngeal position for classical singing?
the one that allows the larynx to remain at or very slightly below its natural resting place
 

How does the vertical position of the larynx change as we age? Be specific.
the larynx descends through a person's life, at birth the base of the cricoid is located at the level of the third cervical vertebra, at age five it descended to C5, at puberty the larynx lowers to C7
 

What is tracheal pull (tug)?
the descending diaphragm pulls down the lungs, bronchial tubes, trachea, and larynx
 

Which nerves serve the larynx?
the vagus nerve and the recurrent laryngeal nerve