Chapter 5

Question 1

Identify the three paired and three unpaired laryngeal cartilages.

Answer 1

The three paired cartilages are the arytenoid cartilages, corniculate cartilages, and cuneiform cartilages. The unpaired cartilages are the cricoid and thyroid cartilages and the epiglottis.

Question 2

Describe the three functions of the larynx.

Answer 2

The three functions of the larynx are to protect the lungs from foreign body entry, phonate by use of the vocal folds, and aid in respiration by regulation of airflow/stablization.

Question 3

Describe separately the general functions of the intrinsic and extrinsic laryngeal muscles.

Answer 3

The intrinsic muscles are responsible for vocal fold movement, regulation of fundamental frequency and vocal intensity and quality, and aerodynamic regulation. The general function of the extrinsic laryngeal muscles is to adjust laryngeal positioning in the neck and to stabilize it.

Question 4

To what do the terms “abduction” and “adduction refer? What muscles control these actions?

Answer 4

Abduction is the opening of the vocal folds, and adduction is their closing. There is only one muscle that abducts the vocal folds, the posterior cricoarytenoid, and there are three muscles that aid in the adduction of the vocal folds, which are the lateral cricothyroid, the transverse arytenoid, and the oblique arytenoid muscles.

Question 5

Identify the supra and infrahyoid muscles and their functions.

Answer 5

The extrinsic laryngeal infrahyoid muscles are the sternothyroid, sternohyoid, and thyrohyoid muscles (the omohyoid and inferior pharyngeal constrictor are also infrahyoid muscles but not considered laryngeal muscles). The suprahyoid muscles are the stylohyoid, mylohyoid, geniohyoid, and digastric muscles (and sometimes the middle pharyngeal constrictor is included). The suprahyoid muscles are not considered extrinsic laryngeal muscles, but their function is to move and stabilize the hyoid bone. The infrahyoid muscles adjust the position of the larynx within the neck and stabilize it.

Question 6

Define glottis, subglottis, and supraglottis.

Answer 6

The glottis is the space between open vocal folds, the subglottis is the airway below the vocal folds, and the supraglottis is the airway above the vocal folds.

Question 7

Identify the three layers of the lamina propria and describe their composition.

Answer 7

The three layers of the lamina propria are the superficial lamina propria, the intermediate lamina propria, and the deep lamina propria. The superficial layer is composed of disorganized and loosely arranged elastin fibers, the intermediate lamina propria is composed of densely distributed and organized elastin fibers, and the deep layer of the lamina propria is made up of tightly packed collagen fibers.

Question 8

Define Reinke’s space.

Answer 8

Reinke’s space is another name for the superficial lamina propria layer of the vocal folds. It is the layer of the vocal folds that has a gelatinous consistency and is composed of randomly arranged elastin fibers and extracellular matrix.

Question 9

Describe the body-cover mechanical model of the vocal folds.

Answer 9

The body-cover mechanical model of the vocal folds groups the vocal folds into a body and a cover. The body is made up of the deep lamina propria and the thyroarytenoid muscle, and the cover is composed of the epithelial layer, superficial lamina propria, and the intermediate lamina propria.

Question 10

Describe the three-layer mechanical model of the vocal folds.

Answer 10

The three-layer mechanical model of the vocal folds groups the five histologic layers into three mechanical layers. The first layer is composed of the epithelium and superficial lamina propria, and is known as the mucosa, and the second layer, called the transition (vocal ligament), is composed of the intermediate and deep lamina propria layers, and the third layer, known as the body, is made of the thyroarytenoid muscle.

Question 11

What is the function of the cricothyroid joint, and what effect does movement of the joint have on the vocal folds?

Answer 11

The cricothyroid joint permits rotation. When the cricothyroid muscle contracts, it rotates the thyroid cartilage downwards and forwards. Movement of the pars recta and pars oblique will elongate the vocal folds and increase tension (changing pitch), and the forward gliding motion of the thyroid cartilage also aids in their adduction.

Question 12

What types of movements are made by the cricoarytenoid joints and what is the result of those movements?

Answer 12

They allow the arytenoid cartilages to rock, enabling the adduction and abduction of the vocal folds, and they can also slide, which gives more control of vocal fold tension and position.

Question 13

Identify the cranial nerve that supplies neural input to the larynx.

Answer 13

The vagus nerve supplies neural input to the larynx.

Question 14

Which muscles are innervated by the recurrent branch of the vagus nerve?

Answer 14

All of the intrinsic laryngeal muscles except the cricothyroid muscle.

Question 15

Which muscle is innervated by the superior laryngeal branch of the vagus nerve?

Answer 15

The cricothyroid muscle.

Question 16

Describe the Bernoulli effect.

Answer 16

Bernoulli’s effect says that in a fluid under movement, the pressure exerted by the fluid on a surface decreases as the velocity of the fluid across the surface increases (to quote the book, “Imagine two canoes sitting quietly side by side in the water. If they are very close to each other, the boats will repeatedly “bonk” together - hit each other and bounce off, only to be drawn together and bonk again, repeating this cycle over and over again. What is occurring? The water flowing between the boats is effectively flowing through a narrowed tube. Therefore, the rate of flow must be increased, and the Bernoulli effect shows us that the pressure within the flow must be decreased. The greater pressure of the water flowing on the opposite side of the boats together with the lesser pressure of the water between the boats will effectively draw the boats together).

Question 17

Describe a cycle of vocal fold vibration using the updated myoelastic aerodynamic theory.

Answer 17

The arytenoid cartilages rock inward to adduct the vocal folds, and as the thoracic cavity is compressed for exhalation, the lung pressure below the glottis increases. This increased pressure pushes against the vocal folds, and when it’s high enough to overcome the vocal fold resistance, it pushes the vocal folds laterally to open the vocal folds (inferior border separates before the superior border - convergent shape). When the glottis opens, air flows through, and because the lung pressure is greater than the supraglottal pressure, there’s a pressure drop (Venturi effect). The glottis shape then becomes an inverted triangle (divergent shape) and creates the Bernoulli effect.

Question 18

What is the relevance of the convergent and divergent-shaped glottis during phonation?

Answer 18

The convergent-shaped glottis facilitates a relatively high lung pressure that forces the vocal folds laterally, and the divergent-shaped glottis helps to create the Bernoulli effect.

Question 19

How do the restorative forces of the vocal fold tissues contribute to vibration?

Answer 19

The restorative forces of the vocal folds help them return back to their original shape and bring them back towards the midline, which will aid in vibration.

Question 20

Define shear force.

Answer 20

Shear force is a force acting parallel to a surface that contributes to the upheaval of tissue described as the mucosal wave. It’s a force that causes one layer to move or deform relative to another. One force tries to slide in one direction, while the adjacent part resists this movement in the opposite direction.

Question 21

Define viscoelasticity.

Answer 21

Viscoelasticity refers to the elastic resistance of the vocal folds and the ease with which they return to their original position and shape.

Question 22

Explain the out-of-phase movement of the mucosal wave.

Answer 22

In the closing phase of the glottis, the inferior border of the vocal folds contacts before the superior border does.

Question 23

Why is the transglottal pressure often referred to as the driving pressure of vibration?

Answer 23

Transglottal pressure is referred to as the driving pressure of vibration because the transglottal pressure is the relative difference between the pressure just below and just above the vocal folds, and this difference in air pressures is the driving force that sets the vocal folds into vibration.

Question 24

Explain why vocal fold closure is important.

Answer 24

Glottal closure, as achieved by vocal fold closure, causes the acoustic excitation of the air in the vocal tract, which is important for phonatory purposes.

Question 25

Define glottal volume velocity and glottal waveform.

Answer 25

Glottal volume velocity is the volume of air flowing through the glottis as a function of time during phonation, and a glottal waveform plots glottal volume velocity.

Question 26

Define glottal resistance and provide a synonym.

Answer 26

Glottal resistance, also known as laryngeal airway resistance, is the measurement of how much resistance the vocal folds provide to the airflow.

Question 27

What is phonation threshold pressure, and what is an average value for it?

Answer 27

Phonation threshold pressure is the minimal lung pressure that is required for phonation. To initiate phonation generally necessitates a lung pressure of 0.3 to 0.5 kPa, and 0.1 to 0.2 kPa less to sustain it.

Question 28

Name and describe the three types of phonation onset.

Answer 28

The three types of phonation onset are simultaneous (gentle) onset, breathy (aspirate) onset, and glottal attack. Simultaneous onset occurs when phonation happens with simultaneous exhalation and adduction of the vocal folds at the midline. Breathy onset occurs when the exhalation and airflow through the glottis are initiated before the vocal folds are closed. A glottal attack happens when the vocal folds are firmly approximated prior to the initiation of phonation.

Question 29

What is vocal rise time?

Answer 29

Vocal rise time is the time between the onset of a sound to the moment when the amplitude of the acoustic sound pressure wave reaches a steady rate.

Question 30

Define stress and strain.

Answer 30

- Stress is force per unit area and can be thought of as the opposite of relaxation. It’s the internal force that results in a shape or volume change after a material has been subjected to external forces, and it tends to displace material. - Strain is the length of tissue change in the direction of the force divided by its resting length.

Question 31

Define linearity.

Answer 31

Linearity refers to the relationship of forces; the reaction to a force is directly proportional to the force applied (when the output is directly proportional to the input).

Question 32

Explain two notable features of the stress-strain curve as they relate to vocal fold vibration.

Answer 32

- The first notable feature of the stress-strain curve is that the vocal folds do not react linearly when they’re stretched (this occurs because of muscle physiology, as when length increases, muscles become more stiff). - The second is that the upward slope of the curve when the muscle stretches is different from the downward slope of the curve when the muscle is released and contracts back to its resting position/length.

Question 33

Define fundamental frequency, provide its symbol, and give average values for adult men, women, and children.

Answer 33

- Fundamental frequency is the rate of vibration of the vocal folds, and its symbol is f0. - For habitual speaking, the average fundamental frequency values for men and women are 115 Hz and 215 Hz, respectively. - For boys with a mean age of 5.6 years, it’s 240 Hz, and for a mean age of 10.5 years, it’s 220 Hz. - For girls with a mean age of 5.6 years, it’s 243 Hz, and for a mean age of 11.2 years, it’s 238 Hz.

Question 34

What factors regulate the natural resonance of the vocal folds?

Answer 34

Vocal fold tension (stiffness), which is regulated by their length (the cricothyroid joint regulates length), and mass per unit volume. So vocal fold length, tension, and mass interact to achieve the target frequency of vibration.

Question 35

What factors regulate change in fundamental frequency?

Answer 35

Vocal fold length, the tension exerted upon their mass per unit length, and their stiffness.

Question 36

Under what circumstances does the body of the vocal folds vibrate along with the cover?

Answer 36

The body of the vocal folds may vibrate along with the cover when speaking in the lower frequencies or when phonating with moderate to high intensity. The thyroarytenoid muscle participates in voice production of moderate to high intensities at any fundamental frequency.

Question 37

What is the contribution of lung pressure to the control of fundamental frequency?

Answer 37

Lung pressure may affect the amplitude of lateral movement of the vocal folds, because the greater the lung pressure, the greater the lateral stretch. The increase in the vocal fold strain increases the tissue stress, increasing elastic recoil force, increasing snap-back time, and raising fundamental frequency.

Question 38

What information has EMG data contributed to our understanding of fundamental frequency control?

Answer 38

EMG data has provided evidence of a correlation between the activity of the cricothyroid muscle with a change in fundamental frequency. It’s also provided indications that other intrinsic muscles (thyroarytenoid, lateral cricoarytenoid, posterior cricoarytenoid) and extrinsic laryngeal muscles are involved in the regulation of fundamental frequency (sternothyroid, thyrohyoid, geniohyoid).

Question 39

How is intensity regulated?

Answer 39

Lung pressure is the major regulator of intensity, as an increase in lung pressure equates to increased air escaping through the glottis during phonation. In that way, vocal fold closure/tension is also a critical factor in intensity regulation. The duration of closure, speed of closure, and degree of closure all contribute to intensity levels.

Question 40

Provide average values of intensity for habitual speaking, soft, and loud phonation.

Answer 40

- Lung pressure during speech averages 0.7 kPa, with a range of 0.3 to 1.2 kPa. Moderate speech is achieved with lung pressures of 1.0 kPa, and 3.0 kPa is typical for louder speech. - Subglottal values are as follows: soft speech has a mean of 3.8 for men and 4.1 for women, typical speech 7.8 for men, and 10.2 for women, and loud 14.9 for men and 19.8 for women, measured in cmH20.

Question 41

Define the Lombard effect.

Answer 41

The Lombard effect is the tendency for an individual to raise their voice (increase their vocal intensity) in an environment where there is lots of surrounding noise.

Question 42

Define tensile stress.

Answer 42

A passive force exerted on the vocal folds due to contraction of the cricothyroid muscle. It’s the greatest force per unit of area of the vocal folds, and it’s a longitudinal force applied in the anterior-to-posterior direction, parallel to the fibers of the lamina propria and muscle.

Question 43

Define contractile stress.

Answer 43

An active stress that’s a function of the elongation/strain of the vocal folds.

Question 44

Define impact/collision stress.

Answer 44

Occurs from the impact of the vocal folds at the midline. It’s greater with increased lung pressure. A collision stress of 0.5 to 5.0 kPa may be achieved with habitual speaking. Applied perpendicularly.

Question 45

Define inertial stress.

Answer 45

Interarytenoid contact stress. It’s less than collision stress (1-2 kPa during typical speech).

Question 46

Define aerodynamic stress.

Answer 46

The air pressure within the glottis during the open phase of phonation, which, at high intensity, can reach as high as 5 to 6 kPa, but will be minimal during conversational speech intensities.

Question 47

Define shear stress.

Answer 47

A force applied parallel to the vocal fold surface due to the upheaval of tissue that forms the mucosal wave. It increases with greater amplitude of vibration and decreases with increasing vocal fold length.

Question 48

Define voice quality.

Answer 48

Voice quality is the listener’s perception of the voice they hear. It is the sum of laryngeal and vocal tract influences.

Question 49

What are phonotraumatic voice disorders?

Answer 49

Phonotraumatic voice disorders are disorders that arise from voice use patterns that cause excessive stress to the vocal folds.

Question 50

Name two other categories of voice disorders other than phonotrauma.

Answer 50

- Dysregulated laryngeal muscle activity, also known as muscle tension dysphonia, which is abnormal muscular activity (excessive squeezing of the vocal folds or lack of contact due to muscle activity) - Malignant disease/cancer of the larynx, which will result in abnormal larynx functioning.

Question 51

Explain why breathiness and reduced loudness are common symptoms of dysphonia.

Answer 51

Dysphonia simply means an abnormal voice. Considering this, breathiness, which occurs when the vocal folds do not close completely during a cycle of vibration, and difficulty in loud voice production, which requires significant subglottal pressure buildup, would be the most common abnormalities. If someone has a breathy vocal quality, this immediately comes with reduced loudness because the vocal folds aren’t closing to allow for proper pressure buildup beneath the vocal folds.

Question 52

How does the study of speech and voice science inform clinical practice?

Answer 52

The study of speech and voice science informs clinical practice greatly because it provides an understanding of the normalities versus the abnormalities concerning the voice, which allows for proper diagnosis and gathering of information to formulate an appropriate treatment plan.