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Physiology of Phonation

Unpaired Cartilages
Paired Cartilages

UNPAIRED CARTILAGES

A. Anterior Cricoid Arch

  • provides clearance for vocal folds

  • thinner compared to posterior part of cricoid cartilage

  • enables movement of vocal

         folds

B. Posterior Quadrate Lamina

  • provides posterior elevation

  • Superior surface of posterior

         quadrate lamina provides

         point of articulation for the

         arytenoid cartilages

 C. Articular Facets

  • located at the lateral surface

         of the cricoid cartilage

  • marks point of articulation for

         the inferior cornua or horns of

         cricoid cartilage, forms cricothyroid joint

D. Cricothyroid Joint

  • pivoting joints permitting rotation of the two structures 

Cricoid Cartilage Landmarks

Cricoid Cartilage Landmarks

PAIRED CARTILAGES

Aryetenoid Cartilage Landmarks

  • ride on upper surface of cricoid cartilage, forming posterior point of attachment for vocal folds

  • Provides mechanical structure that permits onset and offset of voicing

    • On superior surface is corniculate cartilage, projecting posteriorly to form peak of distorted pyramid

 

A. Base

  • inner surface

  • slightly wider than Apex

B. Vocal process

  • project anteriorly

toward thyroid notch

  • Point of attachment for posterior portion of vocal folds

C. Muscular process

  • Forms lateral outcropping of arytenoid cartilage

  • Point of attachment for muscles that adduct and abduct vocal folds

Thyroid Cartilage Landmarks

A. Thyroid Laminae

  • largest of the paired cartilages

  • prominent anterior surface made up of 2 plates of thyroid lamina 

  • joined at midline with the thyroid angle 

B. Thyroid Notch

  • superior most part

  • Adam’s apple (more prominent in males)

C. Oblique line

  • lateral superficial aspect of thyroid lamina

D. Inferior and Superior Cornua

  • inferior connects with the thyroid articular facet of cricoid

Thyroid Cartilage Landmarks

Corniculate Cartilage

  • Rides on superior surface of each arytenoid and are prominent landmarks in the aryepiglottic folds

Cuneiform Cartilage

  • resides within aryepiglottic folds, provides a degree of rigidity to the folds

  • small cartilage embedded within aryepiglottic folds

  •  Situated above and anterior to corniculate cartilages and causes a small bulge on surface of membrane that looks white under illumination

  • Provides support for membranous laryngeal covering

Epiglottis

Epiglottis

A. Thyroepiglottic Ligament

  • Attaches epiglottis  to inner thyroid cartilage, inferiorly to thyroid notch

B. Hyoepiglottic Ligament

  • Attaches epiglottis to hyoid corpus

C. Glossoepiglottic Folds

  • Epiglottic attachment to tongue, overlay of mucous membrane on these ligaments produce vallecu

D. Valeculae

  • Little valleys between tongue and epiglottis 

E. Internal Laryngeal Nerve

  • Branch of vagus nerve (CN X) that conduct sensory information from larynx

F. CN X

  • Vagus nerve

G. Lingual Surface

H. Laryngeal Surface

I. Suprahyoid

  • Open anteriorly, freely

J. Infrahyoid

  • Not free, not exposed

HYOID BONE

Hyoid Bone

  • Articulates with thyroid cartilage by pair of superior processes

  • Forms union between tongue and laryngeal structure

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  • 3 major elements:

  • Corpus/Body

    • prominent shield like structure forming the front of hyoid bone

    • point of attachment of different neck muscles

  • Greater Cornu

    • lateral surface

    • larger horn 

  • Lesser Cornu

    • smaller horn

    • junction of corpus

    • attached muscles

Tensors

Tensors​

  • tenses the vocal folds

Relaxer

2 MUSCLES THAT TENSES THE VOCAL FOLDS :

2 Muscles that tenses the vocal folds

THYROVOCALIS MUSCLE 

  • Medial Thyroarytenoid Muscle

RELAXER

Relaxer

  • Opposite of tensors

THYROMUSCULARIS MUSCLE

  • Lateral Thyroarytenoid Muscle

Thyrovocalis (Medial Thyroarytenoid)

Origin

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Course

Insertion

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Innervation

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Function

Inner surface, thyroid cartilage near notch

Posteriorly

Lateral surface of the arytenoid vocal process

Recurrent laryngeal nerve, X vagus (Cranial nerve 10)

Tenses vocal folds

Thyromuscularis (Lateral Thyroarytenoid)

Origin

​

Course

Insertion

​

Innervation

​

Function

Inner surface, thyroid cartilage near notch

Posteriorly

Base and muscular process arytenoid vocal cartilage

Recurrent laryngeal nerve, X vagus (Cranial nerve 10)

Relaxes vocal folds

CRICOTHYROID MUSCLE

CRICOTHYROID MUSCLE

Origin

​

​

Course

​

Insertion

​

​

Innervation

​

Function

Anterior surface of the cartilage beneath the arch

Superiorly, Externally

Lower surface of the thyroid lamina

Cricothyroid,

Pars Recta

Cricothyroid,

Pars Oblique

Cricoids cartilage lateral to pars recta

 

Superior-obliquely

 

Thyroid cartilage between laminae and inferior horns

External branch of superior laryngeal nerve of X vagus (Cranial nerve 10)

Depresses thyroid relative to cricoid “rocking down motion” (moves the thyroid slightly anteriorly, slightly forward & downward);  tenses vocal folds (vocal folds stretch = tense)

AUXILIARIES

Auxiliaries

  • Muscles that help either:

    • in the relaxation of the vocal folds​

    • in the abduction of the vocal folds

    • in the adduction/constriction of the whole airway

Auxiliaries

Superior Thyroarytenoid

Origin

​

​

Course

​

​

Insertion

​

​

Innervation

Function

Inner angle of thyroid cartilage

Posteriorly

​

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Muscular process of arytenoid

Thyroepiglottic muscle

Aryepiglottic muscle

Inner surface of thyroid cartilage

Posteriorly - Superiorly

Continuation of oblique arytenoid muscle from arytenoid apex

Posteriorly - Superiorly as muscular component of Aryepiglottic fold

Lateral epiglottis

(sides of the epiglottis)

Lateral epiglottis (sides of the epiglottis)

Perhaps relaxes vocal fold

Dilates airway (keeps the epiglottis in place)

Constricts laryngeal opening (moves the epiglottis nearer to the laryngeal opening)

Laryngeal Joints

Cricothyroid joint 

  • Synovial joint that allows the cricoid and thyroid to rotate relatively to each other 

  • It allows the thyroid to rock down anteriorly 

  • Similar movement when flexing the neck 

  • Glides the cricothyroid anteriorly and slightly posteriorly relative to the cricothyroid 

  • Changes in vocal pitch 

Laryngeal Innervation 

  • Superior Laryngeal Nerve 

  • Internal branch

  • Sensory nerve of muscles above the vocal folds

  • External branch

  • Innervation to the cricoid cartilage 

  • Recurrent Laryngeal Nerve 

  • Courses through inferiorly but comes back anteriorly

  • Is the efferent motor control to all intrinsic muscles except the cricoid cartilage

  • Sensory to muscles inferior to the vocal folds 

Cricoarytenoid joint

  • Joint formed by the cricoid and arytenoid cartilages 

  • Synovial joint, rocking, gliding and minimal rotation of the arytenoid cartilage   

  • Access of the motion of the cricoid cartilage is round 

  • Rocking action brings the 2 vocal processes together permitting adduction of the vocal folds

  • Arytenoids can also glide along the long axis facet changing the length of the vocal fold permitted by the cricoarytenoid joint 

  • Enable rotation upon the vertical axis and the extremes of abduction 

 

Both joints allow the abduction and adduction of the vocal folds

Laryngeal Joints

Intrinsic Muscles

Lateral Cricoarytenoid

Lateral Cricoarytenoid

Intrinsic Muscles

Lateral Cricoarytenoid

Lateral Cricoarytenoid

LARYNGEAL ELEVATORS

SUPRAHOID MUSCLES

  • muscles that attached to the structures above the hyoid

  • Includes several muscles

Suprahoid Muscles
Laryngeal Elevators

* it is also an intrinsic lingual muscle (intrinsic tongue muscle)

* like hyoglossus, it is also an intrinsic lingual muscle (intrinsic tongue muscle); may also affect the movement of the tongue

LARYNGEAL DEPRESSORS

INFRAHYOID MUSCLES

  • Muscles that come from/originates from the hyoid to structures below the hyoid

Laryngeal Depressors
Infrahyoid Muscles

* Since it comes from the sternum in the clavicle when it contracts the muscle will now pull the hyoid inferiorly.

* located in a single plane, similar to oblique arytenoid and Aryepiglottic muscle. When the larynx is elevated; this can help elevate the rib cage or the sternum in the clavicle. But when the sternum is fixed, it can pull the hyoid and the thyroid inferiorly.

* they cannot act their own; the must act together in its function

Theories on Phonation

  • How do we produce voice ?

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Body Cover Theory

  • Vocal folds are composed of 5 histological layers

  • They get progressively stiffer as you go deeper into the TVF

  • Innermost layer: Muscular layer, Outermost layer: Mucosa

  • The stiffest would be the muscles: thyrovocalis

  • Explains that your TVFs have technically three functional layers: cover (composed of squamous epithelium or mucosa, superficial lamina propria), transitional layer (vocal ligament), body (vocalis muscles)

  • BCT explains that the superficial lamina propria or bracheas spec vibrates around the muscle so the muscle provides the structure but the cover acts as the one that moves freely and the one that vibrates

 

Bernoulli Effect

  • At a point of constriction there will be a decrease in pressure perpendicular to the flow and an increase in velocity of the flow.

  • When you constrict something, the pressure increases, and the flow decreases up to a certain point when the contraction is released, the pressure will then drop but it will cause the velocity of the flow of air to accelerate. 

 

Myoelastic-Aerodynamic Theory

  • When the vocal folds adduct, the subglottal pressure builds up until the covers blow apart. When

         the superficial lamina propria and squamous

         epithelium blows/ opens up from the middle,

         air molecules escape from the center freely. 

  • The air molecules in the side bump into the

         TVF’s sides, because of that, there is an

         increase in speed of the airflow. The increased

         speed along the sides of the TVF, decrease

         the static pressure alongside the sides

  • Upon that, the sides then get sucked together,

         bringing the two vocal fold covers back into the

         midline, which is an example of the bernoulli effect

  • The covers will also go back in the middle because of the elastic recoil

  • At rest, it will go back to the original position

  • When you vocal cords are abducted, the pressure builds up and will now froce your covers to open and because of the elastic nature and the bernoulli effect, the covers will start to close and will accelerate the air coming out of the glottis. And then it will go back to its adducted position.

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Myoelastic: Muscle that is covered by a elastic layer, which is the superficial lamina proprea, squamous epithelium, intermediate and deep lamna propeas 

Aerodynamic: Following the bernouli’s principle

Body Cover Theory

Phonatory Cycle:

  1. Air pressure beneath the vocal folds will rise from the respiratory tract. Air pressure causes the vocal folds to separate in the inferior portion. The covers will slightly separate/move laterally

  2. The superior aspect of the vocal folds will now begin to open because of the pressure build up

  3. The vocal folds will open and the flow between the folds increases, while the flow at the folds, decreases. A high pressure to lower pressure, so when the constriction point is released, the point of constriction will have a lower pressure than the higher pressure area below it.

  4. Then, the decreased pressure and elastic quality of the vocal folds will cause the folds to go back to the middle so when the vocal folds are in the midline the body cover will now contacts inferiorly with each other

  5. The cycle then repeats 

 

Planes of Vibration

  • The vibration of the body cover of the TVF can be described with three characteristics: anterior & posterior vibrations (meaning, when the vocal folds adduct, it starts with the anterior since it is the least amount of distance relative to each side. to the posterior end that has the most distance. Your anterior space of the vocal folds in the midline of the glottis is lesser than the space or the distance of the vocal folds where the arytenoid are located), mediolateral waves (mucosal waves, when the covers meet in the midline. First point of contact is the anterior â…“ then posterior â…”. This is vulnerable to misuse and very disruptive closures, this is where conditions like nodules would develop), and inferior-superior vibrations (glottal wave, opens up coming from the anterior moves superior, because of its elastic nature, the inferior sid will meet again first and then disappear. Glottal wave is the vertical wave of vibration)

 

MUCOSAL WAVE: MEDIALATERAL VIBRATIONS

GLOTTAL WAVE: INFERIOR-SUPERIOR VIBRATIONS

Bernoulli Effect & Planes of Vibration
Theories on Phonation
Phonatory Cycle
Myoelastic-Aerodynamic Theory

Properties of Voice

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Vocal Register - range of tones in the human voice that is produced by a particular vibratory pattern of the vocal folds. These different types of registers would be:

  • Modal, register for regular speech. Should match a person’s age or gender, build and size of the speaker

  • Falsetto, increased in length and tension of the vocal folds. Particularly, if it tenses, it makes a longitudinal gap, making a high-pitched voice that we know as falsetto. Take note that falsetto is commonly and appropriately used in singing, but it is not normal in normal speech.

  • Whistle

  • Vocal / Glottal Fry, when there is a decrease in length of the vocal folds and increase in tension of the lateral borders of the vocal folds. There is also a relaxed middle border of the vocal folds. Because of the differences in tension, there will be an unnaturally low pitched voice that will be produced like a motorboat. This is not normal for both singing and speech

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Vocal Pitch - perceptual correlation of frequency. So when we hear a person’s voice and we say that they have a high pitch it is the perceptual correlate of frequency

 

Fundamental frequency - formant 0, is the number of cycles per second that the vocal folds vibrate in terms of the number of cycles. As such, the formant 0 is pitch since it is determined by the masss, length, and tension of your folds. So the higher the mass, the lower the fundamental frequency. The more massive, the more lower. 

  • That’s why males usually have massive vocal folds compared to females. That is why males have lower fundamental frequencies as well. 

  • The greater the length of the vocal folds, the higher the frequency. The vocal fold tensors, if they are more tensed or stretched, the higher the fundamental frequency. The more relaxed, the more its lower. 

  • When we are stressed, we usually use a higher pitched voice. 

  • The tensors, the greater the tension of the vocal folds, the higher the frequency

  • The lower the tension, the lower the frequency

 

MORE MASSIVE, RELAXED, SHORT: Lower Frequency

LESS MASSIVE, LONGER, TENSED: Higher Frequency

 

FREQUENCY (EQUIV. PITCH): Hertz

INTENSITY (EQUIV. LOUDNESS): Decibels

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Vocal Pitch Issues

  • Pitch can have issues like vocal fatigue (misuse of voice for singers, cannot reach higher notes), variable pitch (pitch variation is too varied and erratic without patterns), monopitch (no change in tone, may be a result of a pathology)

Vocal Loudness

  • If pitch is the perceptual correlation of frequency, it is the perceptual correlate of intensity which is DECIBELS. In order for sounds to be generated in the vocal folds, it needs to be of high intensity. So to get that high intensity, there needs to be a high buildup of subglottal pressure. 

  • So for people that have whispered or lower voices, there could be a problem in producing their subglottal pressure. 

 

Vocal Loudness Issue

  • There are cases where your voice may be too soft or whispered which is a problem when it its TOO SUDDEN

  • When your voice is too loud, it can be attributed to problems in hearing. This is because people with hearing loss usually uses a louder voice that is higher than normal

  • We also have monoloudness, when the person is talking in a very consistent loudness without changing their loudness

  • We also have variable loudness, when they cannot control how loud or soft their voice is.

 

Vocal Quality

  • Quality, also known as harmonicity, is how your voice is produced smoothly compared to the other sounds that are being produced by your structures when you do phonation

  • Each vocal fold should have symmetrical mass, length, and tension. So if not, one vocal fold would vibrate differently and may produce a different fundamental frequency than the other which would result in a phenomenon called Diplophonia where the person is generating two different sets of fundamental frequencies , so it’s like having 2 voices because of certain conditions and pathologies

  • Vocal fold covers should not come together too loosely as this will result in breathiness, a breathy voice is very airy 

  • Person who Speaks very tightly because the tension is too tense fails to produce the normal optimal vibratory pattern that could be an issue. Vocal fold covers must cover 50% of the cycle. In a range of 40-60% and separate for 40-60% of the cycle as well that's why 50, cover should meet, 50 cover should separate 

  • Aside from the adduction that they meet 50 and move away 50 percent, they should also mirror each other’s movements. For example if a cover moves to the midline, the other should also move to the midline. If the opposite happens, there will be what we call PHASE ASYMMETRY because the gap between the vocal cords will increase that will cause breathiness

 

Vocal Quality Issues

  • Hoarseness, can be characterized by breathiness or strained. Described as a very rough sounding voice and intelligible since the pitch and loudness is relatively appropriate but the voice is ROUGH, sometimes BREAKS

  • Strain, very tense in speaking and sounding like you are strangled or suffocating

  • Breathiness, super airy 

  • Diplophona, Simultaneous presence in the voice of two separate tones, heard as distinctly different in pitch

Properties of Voice
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