EXAM #1: ANATOMY & PHISOLOGY & VOCAL FOLD VIBRATIONS

EXAM DATE: SEPT. 24

Framework of the Larynx

• Larynx is made up of cartilages held together by

  • elastic membranes and ligaments

  • muscles

• The laryngeal tissues (cartilage and muscle) are lined by a mucous membrane

Borders of the Larynx

• Larynx is attached to the hyoid bone superiorly

• Larynx is attached to the trachea inferiorly

• Larynx is surrounded by muscles called the extrinsic muscles of the larynx

T/F

The Larynx is surrounded by muscles called the intrinsic muscles of the larynx

False: it is surrounded by extrinsic muscles.

9 cartilages

• 3 single

• 6 paired

How many cartilages are in the larynx?

What are the 3 single cartilages of the larynx?

• epiglottis

• thyroid

• cricoid

What are the 6 paired cartilages of the larynx?

• Arytenoids

• Cuneiform

• Corniculate

T/F

The thyroid is the largest cartilage of the larynx.

True

In a location term, which part of the word is indicative of the insertion point and which one is for the origin point?

• Origin: beginning

• Insertion: Ending

• Example: Thyrohyoid: the origin is the thyroid and the insertion is the hyoid

Thyroid Cartilage

• Single cartilage

• attached to the hyoid bone via the thyrohyoid membrane

Epiglottis

• It is attached to the thyroid membrane and hyoid bone

• Thin and leaf-shaped or heart-shaped

• Posterior to the base of the tongue and hyoid bone; anterior to the laryngeal inlet

• attached to the thyroid cartilage via the thyroepiglottic ligament

• attached to the hyoid bone via the hyoepiglottic ligament

• folds over the larynx during swallowing to direct food around the larynx (blocks the airway to protect the trachea and avoid the trachea)

Cricoid Cartilage

• Single, unpaired cartilage

• Shaped like a signet ring

  • Posterior part: cricoid lamina

  • Anterior part: cricoid arch

• attached to the thyroid cartilage via the median cricothyroid ligament

• attached to the trachea via cricotracheal ligament

Cricothyroid Joint

• Where the cricoid cartilage joins the thyroid cartilage

• There is movement at this point

• cricothyroid ligament holds the joint together

T/F

The cricothyroid joint and ligament are different structures.

True

T/F

There is no movement in the cricothyroid joint.

False, there is movement because it is a joint.

Arytenoid Cartilages

• paired, one on each side

• shaped like pyramids

• base of the arytenoids sit on top of the cricoid lamina

  • form the cricoarytenoid joints

What are the two processes on the base of the arytenoids?

• Vocal Process- closer to the midline

• muscular process- away from the midline

T or F

The apex is the top of the pyramid (arytenoid).

True

What two cartilages sit on top of the apex of the arytenoid cartilages?

• cuneiform cartilages

  • closer to the midline

  • very tiny

• corniculate cartilages

  • on top of pyramid

Cricoarytenoid Joints

• Where the base of the arytenoid cartilages meet the top of the lamina of the cricoid cartilage

• Joint so movement occurs at this point

• held together by the cricoarytenoid ligament

  • Posterior cricoarytenoid ligament

  • Anterior cricoarytenoid ligament

What are the fucntions of the intrinstic muscles of the larynx

• Affect the shape of the glottis (opening between the vocal folds)

• Affect the vibration of the vocal folds

T/F

If you can contract any muscle, the point of insertion will reach the point of origin.

True

Example: if the muscles was JamesBond, then bond would get closer to James

True Vocal Folds

• Involved in airway protection and vibration for speech

• Primary Function: biological

• Secondary Function: phonation

• Is Comprised of 2 muscles

What are the three parts of a true vocal folds

• Thyrovocalis

• thyromuscularis

• vocal ligament

False Vocal Folds

• Involved in airway protection

• above ( superior to) the true vocal folds

Thyroarytenoid Muscles

• Make up the bulk of the true vocal folds

• origin: thyroid cartilage

• insertion: arytenoid cartilages

• Innervated by the recurrent laryngeal nerve- branch of Vagus Nerve (CN X)

Adduct vs Abduct of Vocal Folds

• Adduction: Vocal folds @ midline

• Abduction: moving away from midline

What are the primary adductors?

• Lateral Cricoarytenoid (LCA)

• Interarytenoid Muscle (IA)

What are the primary abductors?

Posterior cricoid arytenoid (PCA)

Thyroarytenoid Muscles: Area

• Two parts

  • Thyrovocalis

    • Closer to the midline

    • Origin: thyroid cartilage just below the thyroid notch

    • Insertion: the vocal process of the arytenoid cartilages

  • thyromuscularis

    • Lateral

    • Origin: thyroid angle

    • Insertion: the base of the muscular process of the arytenoid cartilages

Thyroarytenoid Muscles: Functions

• Thyrovocalis

  • plays a role in vocal fold tension

  • can increase internal tension without changing the length of the vocal fold

  • Increase tension = increase pitch

• thyromuscularis

  • plays a role in adducting the vocal folds (brings them together)

  • pulls arytenoid cartilage closer to the thyroid

Vocal Ligament

• Third part of the true vocal folds

• Elastic structure on the medial edge of the thyrovocalis

• Runs between the vocal process of the arytenoid cartilages and the thyroid cartilage (immediately below the thyroid notch)

Movement at the Cricoarytenoid Joint

• Permits rocking movement and limited gliding movement (along the cricoid)

• Rocking causes:

  • Upward and outward swinging movement of the vocal processes during abduction of the vocal folds

  • Downward and inward swinging movement of the vocal processes during adduction of the vocal folds

Downward —> Inward

upward —> outward

Lateral cricoarytenoid muscles (LCA)

• Origin: Upper border of the lateral arch of the cricoid cartilage

• Insertion: Anterior surface of the muscular process of the arytenoid cartilage

• Function: rotates the arytenoid cartilage, drawing muscular process forward and vocal process medialward

• Innervated by the Recurrent Laryngeal Nerve – branch of Vagus Nerve (CN X)

What nerve innervates the intrinsic muscles?

ON EXAM

Recurrent Laryngeal Nerve—branch of vagus Nerve X

What intrinsic muscle only 1 is not innervated?

ON EXAM

Cricothyroid muscles

It is the exemption → innevrated by superior laryngeal branch of vagus nerve

Interarytenoid Muscles

• Transverse Interarytenoid:

  • Broad sheet of muscle, running horizontally

  • Origin: apex to base of one arytenoid cartilage

  • Insertion: apex to base of other arytenoid cartilage

• Oblique Interarytenoid:

  • Paired muscles, forms an X on the posterior aspect of the arytenoid cartilages

  • Origin: apex of one arytenoid cartilage, crosses over and inserts

  • Insertion: base of the other arytenoid cartilage

• Function of both: adducts the arytenoid cartilages

• Innervated by the Recurrent Laryngeal Nerve – branch of Vagus

Posterior Cricoarytenoid Muscles (PCA)

• Origin: Lamina of cricoid cartilages

• Insertion: Posterior aspect of muscular processes of arytenoid muscles

• Function: Pulls muscular process diagonally downward and toward the midline

  • Abducts the arytenoid cartilage

  • Primary vocal fold abductor (moves vocal folds away from one another)

• Innervated by the Recurrent Laryngeal Nerve – branch of Vagus

Cricothyroid Muscles

• Located on the outer surface of the larynx

• Origin: arch of cricoid cartilage

• Insertion: caudal margin of the thyroid cartilage

• Innervated by the Superior Laryngeal Nerve – branch of Vagus

• Two Parts:

  • Pars Recta: more vertical fibers

  • pars oblique: more diagonal fibers

• Function: move the cricothyroid joint

• what happens to the vocal folds: tenses the vocal folds

Movement of the CT Joint

• Contraction of the CT muscle causes the thyroid to rock down and forward – moving

the base of the thyroid cartilage toward the cricoid cartilage and the body of the

thyroid cartilage away from the arytenoid cartilages

• This lengthens and tenses the vocal fold

• Causes an increase in pitch of the voice

Quadrangular Membrane

• Paired structure – one on each side

• Begins on the lateral sides of the epiglottis

• Runs downward to attach to the corniculate cartilages and the medial surfaces of the arytenoids

• End as the free margin of the false folds

Aryepiglottic Folds

• Superior margins of the quadrangular membrane

• Poorly developed aryepiglottic muscles

• Run from the sides of the epiglottis to the apex of the arytenoids on both sides of larynx

• Cuneiform cartilages are embedded in the aryepiglottic folds

Laryngeal Spaces

• Laryngeal vestibule:

  • Space in the larynx above the false vocal folds

• Laryngeal ventricle:

  • Space in the larynx between the false and true vocal folds

• Subglottic space:

  • Space below the true vocal folds to the bottom of the cricoid cartilage

Glottis

• Glottis: space between the true vocal folds and the arytenoid cartilages

• Two parts to glottis:

  • Membraneous glottis: part of the glottis between the vocal folds themselves

    • In adults, comprises 2/3 of the glottis

  • Cartilaginous glottis: part of the glottis between the arytenoid cartilages

    • In adults, comprises 1/3 of the glottis

T/F

The tyrovocalis and the thyromucularis are the two parts of the glottis.

False; Membraneous glottis & Cartilaginous glottis

Conus Elasticus

• Runs from top of true vocal folds to the bottom of the cricoid arch

• Continuous sheet of membrane connecting the thyroid, cricoid, and arytenoid cartilages

  • Formed by the medial cricothyroid ligament, lateral cricothyroid membrane, and the vocal ligament

Breakdown of Myoelastic Aerodynamic Meaning

• Myo = muscles

• elastic = elasticity

• aero= air molecules

• dynamic = movement

T or F

In Myoelastic Aerodynamic Theory of vocal fold vibration, it is combining elasticity and flexibility and movement of air molecules.

True

Role of Muscles in Vocal Fold Vibration

• muscle contraction does play a role on vocal fold vibration

  • LCA, IA, and thyromuscularis contract to adduct the arytenoids (and the vocal folds).

  • CT and thyrovocalis contract to increase tension of folds results in faster vibration.

Vocal Fold Vibration: Overview

• The vocal folds are brought together at the start of vibration by muscles

  • The muscles contract one time at the start of vocal fold vibration to adduct the arytenoid cartilages and vocal processes, thereby adducting the folds

• After that, the muscles remain contracted, holding the arytenoids and vocal processes closed

• The vocal folds vibrate (open and close) due to aerodynamic and elastic forces.

T/F

The theory of vocal fold vibration has 6 steps.

False, it has 5 steps

Theory Breakdown: Vocal Fold Vibration Overview (KNOW)

1. Muscles contract to adduct the arytenoid cartilages (and the vocal folds)

2. Subglottal pressure builds up under the closed vocal folds. 

3. Vocal folds are trying to resist the pressure

4. Vocal folds return to midline by two mechanisms

5. Cycle Repeats at #2

Theory Breakdown: Vocal Fold Vibration Description

• Muscles contract to adduct the arytenoid cartilages (and the vocal folds

  • LCA, IA, thyromuscularis

• Subglottal pressure builds up under the closed vocal folds. Where is this pressure coming from? -

  • Respiratory system

  • pressure will build up underneath the vocal folds

• Vocal Folds are trying to resist the pressure

  • When subglottal pressure (P_s) is greater than

    • atmospheric pressure (P_atmos) AND 

    • the resistance at the level of the vocal folds

  • Then:

    • The vocal folds will be blown apar

    • The airflow through the glottis will be proportional to the driving pressure (P_s)

• The vocal folds will return to midline via two mechanisms:

  • They will recoil back to midline due to their elasticity

  • They will be “sucked” back to midline due to the Bernoulli effect

  • between vocal folds there is negative pressure which allows vocal folds to adduct to the midline.

• Once the vocal folds are closed again, the cycle starts over at #2

  • subglottal pressure begins again

The role of elasticity in vocal fold vibration

• The vocal folds have inherent elastic characteristics

  • When displaced from rest will exert an elastic recoil force to return to rest

The role of aerodynamics in vocal fold vibration

• Refers to the airflow and air pressure generated in the larynx during vibration

• Vocal fold vibration can be a strictly aerodynamic event

  • The vocal folds will vibrate once they are close enough to each other

The role of elasticity in pitch change

• CT and thyrovocalis change elasticity of vocal folds by stretching them or tensing them

• When stretched/tensed, the vocal folds become stiffer

  • Will move less from rest (reduced lateral excursion)

  • Will exert a larger recoil force, so will return to rest more quickly

  • Both of these will result in faster vibration, and therefore a higher pitch

Can someone with one vocal fold paralyzed phonate?

Yes but may have a whispery sound to voice if vocal folds can’t get close enough to one another to touch

Can someone with both vocal folds paralyzed phonate?

• Depends on position of vocal folds

• Paralyzed closed: yes, but can not breathe

• Paralyzed open: no, because vocal folds can not get close enough to one another

• Paralyzed in paramedian position: 

  • yes, but will be weak and have a whispery sound since they can not touch

  • can breathe through space between them but may have inspiratory stridor (noise on inhalation as the air moves through the space between the vocal folds)

Histologic Structure of the Vocal Fold: Superficial to Deep ( KNOW!)

• Epithelium: thin shell, maintains the shape of the vocal fold

• Superficial layer of lamina propria: loose connective tissue, a.k.a. Reinke’s space

• Intermediate layer of lamina propria: elastic fibers

• Deep layer of lamina propria: collagen fibers

• Muscle: TA muscle

Histologic Structure of the Vocal Fold: Deep to Superficial ( KNOW!)

• Muscle: TA muscle

• Deep layer of lamina propria: collagen fibers

• Intermediate layer of lamina propria: elastic fibers

• Superficial layer of lamina propria: loose connective tissue, a.k.a. Reinke’s space

• Epithelium: thin shell, maintains the shape of the vocal fold

Cover Body Theory

• Cover: 

  • Mucosa – epithelium and superficial layer of lamina propria

• Body:

  • Vocal ligament (conus elasticus) – intermediate and deep layers of lamina propria

  • Muscle

• Double-layered vibrator which is affected by the contraction of the CT and TA.

• Comfortable speech:

  • TA contracts a little more than CT.

  • Vibration in both cover and body, but more in cover.

• Will talk more about this when we discuss registers.