Anatomy of Phonation

Ch. 4

Spoken CommunicationVoiceless phonemes or speech sounds-

produced without the use of the vocal folds /s/, /f/

Voiced sounds are produced by action of the vocal folds /z/, /v/

Phonation is voicing, the product of vibrating vocal folds

Respiration is the energy source that permits phonation to occur

Vocal Folds

Made up of five layers of tissue with the deepest layer being muscle

Space between the vocal folds is glottis

Area below the vocal folds is subglottal region

Functions of the LarynxPhonation

Sphincter-vocal folds are capable of a strong and rapid clamping of the airway to keep foreign objects out

Hold your breath

Lifting heavy objects/Childbirth- “fix” or anchor your larynx which provides muscles of upper body a solid framework

Framework of Larynx A musculocartilaginous

structure

Comprised of three unpaired and three paired cartilages bound by ligaments and lined with mucous membrane

Oddly shaped box that sits atop the last ring of the trachea

Adjacent to cervical vertebrae 4-6 in the adult

Average length is 44mm- males, 36 mm- females

Cavities of Larynx

Aditus- entry to the larynx

Vestibule- space between the aditus and the ventricular folds (false vocal folds)

Laryngeal ventricle- middle space of the larynx Lies between the margins

of the false vocal folds and true vocal folds

Cricoid Cartilage Complete ring resting atop

the trachea Most inferior of the laryngeal

cartilages Posterior quadrate lamina-

provides point of articulation for arytenoid cartilages

Lateral surface- point of articulation for inferior horns of thyroid cartilage

Cricothyroid joint- diathrodial, pivoting joint permits rotation of the two structures

Would fit loosely on your little finger

Thyroid Cartilage Unpaired cartilage Largest of the cartilages Articulates with the cricoid

cartilage below Paired processes allow it

to rock forward and backward

Prominent anterior surface made of two places- thyroid laminae

Joined at the midline- thyroid angle

Superior most point is the thyroid notch (adam’s apple)

Thyroid Cartilage Vocal folds attach to the

thyroid just behind the thyroid notch

Posterior aspect is open- two prominent sets of cornu or horns

Inferior cornu project downward to articulate with the cricoid cartilage

Superior corner project superiorly to articulate with the hyoid

Arytenoid Cartilages Ride on the high-backed

upper surface of the cricoid cartilage

Form the posterior point of attachment for the vocal folds

Paired cartilage Vocal processes project

anteriorly toward thyroid notch, posterior portion of the vocal folds attach

Muscular process forms the lateral outcropping of the arytenoid pyramid- point of attachment for muscles that adduct/abduct the vocal folds

Corniculate Cartilage

Corniculate cartilages

Ride on the superior surface of each arytenoid cartilage

Prominent landmarks in the aryepiglottic folds

Epiglottis Unpaired cartilage

Leaf-like structure arises from the inner surface of the thyroid cartilage just below the notch

Attached by the thyroepiglottic ligament

Sides are joined with the arytenoid cartilages via the aryepiglottic folds

Projects upward beyond the larynx and above the hyoid bone

Epiglottis Attached to the root of the

tongue by glosso-epiglottic fold and lateral glosso-epiglottic ligamets

This juncture produces the valleculae

Pyriform sinuses- lateral recesses

Attached to the hyoid bone via the hyoepiglottic ligament

Surface is covered with a mucous membrane lining

Cuneiform cartilages Small cartilages

embedded within the aryepiglottic folds

Situated above and anterior to the corniculate cartilages

Provide support for the membranous laryngeal covering

Hyoid Bone Provides the union between the

tongue and the laryngeal structure

Unpaired small bone

Articulates loosely with the superior cornu of the thyroid cartilage

U-shaped, being open in the posterior side

Corpus or Body- forms the front of the bone, point of attachment for six muscles

Greater cornu- lateral surface of the corpus projecting posteriorly

Lesser cornu-found at the junction of the corpus and greater cornu

Extrinsic ligaments Thyrohyoid membrane-

stretches between the greater cornu of the hyoid and lateral thyroid

Lateral Thyrohyoid ligament-superior cornu of the thyroid to posterior tip of the greater cornu hyoid

Median Thyrohyoid ligament- from corpus hyoid to upper border of the anterior thyroid

Together- these three connect the larynx and the hyoid bone

Extrinsic ligaments

Hyoepiglottic ligament/Thyroepiglottic ligament- attach the epiglottis to hyoid and inner thyroid cartilage, just below the notch

Cricotracheal ligament-attaches the trachea to the larynx

Intrinsic ligaments Connect the cartilages of the

larynx and form the support structure for the cavity of the larynx and vocal folds

Quandrangular membranes Layer of connective tissue

running from the arytenoids to the epiglottis and thyroid cartilage

Form false vocal folds Originate at inner thyroid

angle and sides of epiglottis and form an upper cone that narrows and terminates at the arytenoid and corniculate cartilages

Intrinsic ligaments Aryepiglottic muscles

From the side of the epiglottis to the arytenoid

Form the upper margin of the quadrangular membrane

Form the aryepiglottic folds Folds are simply the ridges

marking the highest elevation of these membranes

Pyriform sinus is the space between the aryepiglottic fold and the thyroid cartilage

Vocal Fold Structure Most superficial layer-

protective layer of epithelium Glistening white appearance Protective layer

Second layer- superficial lamina propria (SLP)- elastin fibers Stretched cushions

Third layer- Intermediate lamina propria (ILP)- elastin fibers running in an A-P

direction provide elasticity and strength

Vocal Fold Structure Fourth layer- Deep lamina

propria (DLP)- Collagen fibers that prohibit

extension

ILP and DLP combine to make up the vocal ligament Stiffness and support

Fifth layer-Thyroarytenoid muscle- active element of the vocal

folds

Mucosal lining- combination of the epithelial lining and first layer

Movement of the Cartilages

Cricothyroid and Cricoarytenoid joints are the only functionally mobile points of the larynx

Cricothyroid joint- junction of cricoid cartilage and inferior cornu of the thyroid cartilage Diarthrodial (synovial) joint that

permit the cricoid and thyroid to rotate and glide

Rotation permits the thyroid cartilage to rock down in front

Permits the thyroid cartilage to glide forward and backward slightly

Provides the major adjustment for change in vocal pitch

Movement of the Cartilages

Cricyarytenoid joint Formed between the cricoid

and arytenoid cartilages Synovial joints permit

rocking, gliding and minimal rotation

Rocking action permits two vocal processes toward each other permitting the vocal folds to approximate

Arytenoids glide on the long axis which changes vocal fold length

Arytenoids rotate upon a vertical axis which permits abduction

Intrinsic Laryngeal Muscles

Have both origin and insertion on laryngeal cartilages

Make fine adjustments to the vocal mechanism

Assume responsibility for opening, closing, tensing, lengthening and relaxing the vocal folds

Movement of the vocal folds into and out of approximation is achieved by the coordinated effort of many of the intrinsic muscles of the larynx

Changing pitch is reflected by a change in mass or tension

Intrinsic Laryngeal Muscles

Lateral Cricoarytenoid Muscle Attaches to the cricoid

and the muscular process of arytenoid

Muscular process will be drawn forward

Rocks the arytenoid inward and downward

Adduction of vocal folds Lengthens the vocal folds Innervated by X vagus

nerve

Intrinsic Laryngeal Muscles

Transverse Arytenoid Muscle Runs between the two

arytenoid cartilages on the posterior surface

Pulls the two arytenoids closer together

Approximates the vocal folds Increased medial

compression which is increased force of adduction

Vital element in vocal intensity change

Innervation by the Recurrent laryngeal nerve of the X vagus

Intrinsic Laryngeal Muscles

Oblique Arytenoid Muscles Paired muscles Originate at the posterior base

of the muscular process and course obliquely up to the apex of the opposite arytenoid

Form an “X” Pull the apex medially Promotes adduction Enforces medial compression Rocks arytenoid and vocal folds

down and in Aids in pulling the epiglottis to

cover the opening to the larynx Innervation- Recurrent

laryngeal nerve of the X Vagus

Intrinsic Laryngeal Muscles

Posterior Cricoarytenoid muscle Sole abductor of the vocal

folds Originates from the

posterior cricoid lamina Project up to insert into the

posterior aspect of the muscular process of the arytenoid cartilage

Pulls muscular process posteriorly

Rocks the arytenoid cartilage

Abducts the vocal folds

Intrinsic Laryngeal Muscles

Cricothyroid Muscle- composed of two heads Pars Recta- originates on the

anterior surface of cricoid cartilage and courses up to the lower surface of the thyroid lamina

Pars oblique- arises from the lateral cricoid cartilage to the point of juncture between the thyroid laminae and inferior horns

Both tense the vocal folds Together they are the major

contributors for pitch change Innervated by the Superior

Laryngeal Nerve of the X Vagus

Intrinsic Laryngeal Muscles

Pars RectaRocks the thyroid cartilage downwardBrings thyroid and cricoid closer together in frontMakes the posterior cricoid more distant from the

thyroidVocal folds are stretched

Pars ObliqueThyroid slides forwardTense the vocal folds

Intrinsic Laryngeal Muscles

Thyrovocalis Muscle (abbreviated as vocalis) Medial muscle of the vocal

folds Originates from the inner

surface of the thyroid cartilage Inserts into the lateral surface

of the arytenoid vocal process Contraction draws the thyroid

and cricoid cartilages farther apart in front

Glottal tensor- tenses the vocal folds

Innervated by the Recurrent Laryngeal Nerve of the X Vagus

Intrinsic Laryngeal Muscles

Thyromuscularis Muscle Paired muscle Immediate lateral to each

vocalis muscle Originates on the inner

surface of the thyroid cartilage near the notch

Inserts into the arytenoid cartilage at the base

Laryngeal relaxer Relaxes the vocal folds Innervated by the

Recurrent Laryngeal Nerve

Extrinsic Laryngeal Muscles

Muscles with one attachment to a laryngeal cartilage

Laryngeal elevators- muscles that elevate the hyoid and larynx

Laryngeal depressors- those that depress the hyoid and larynx

Elevators Digastricus- two separate

bellies- elevates the hyoidAnterior- originates on the inner surface of

the mandible near the point of fusion

Inserts into hyoid hyoid draws up and forward. Innervated by the V Trigeminal

Posterior – originates on the mastoid process

of the temporal bone and inserts into the hyoid at the

juncture of the hyoid corpus and greater cornu

hyoid draws up and back. Innervated by the the VII facial

Elevators Stylohyoid Muscle

Originates on the styloid process of the temporal bone

Courses down and inserts into the corpus of the hyoid

Elevates and retracts the hyoid bone

Innervated by the VII facial nerve

Elevators Mylohyoid Muscle

Originates on the underside of the mandible

Courses to the corpus hyoid

Fanlike muscle Forms the floor of the

oral cavity Innervated by the V

trigeminal nerve

Elevators Geniohyoid

Superior to the mylohyoid

Projects in a course parallel to the anterior belly of the digastricus from the inner mandibular surface down to the hyoid bone at the corpus

Elevates the hyoid and draws it forward

Innervated by the XII hypoglossal nerve arising from the first cervical spinal nerve

Elevators Hyoglossus Muscle

Laterally placed muscle Originates from the

superior surface of the greater cornu of the hyoid and

inserts into the side of the tongue

Innervated by the the XII hypoglossal

Elevators Genioglossus Muscle

Hyoid elevator and tongue depressor

Originates on the inner surface of the mandible and then down

insert into the tongue and anterior surface of the hyoid corpus

Innervated by the XII hypoglossal

Elevators Thyropharyngeus Muscle-

Originates from the thyroid lamina and courses up

Inserts into the posterior pharyngeal raphe

Elevates the larynx Constricts the pharynx Innervated by the RLN of

the X Vagus

Depressors Sternohyoid muscle

Runs from the sternum to the inferior margin of the hyoid

Depresses the hyoid Fixes the hyoid and

larynx Lowering is clearly

evident following the pharyngeal stage in swallowing

Innervated by the ansa cervicalis

Depressors Omohyoid Muscle

Has two bellies Superior belly terminates

on the side of the hyoid corpus

Inferior belly has its origin on the upper border of the scapula

Passes deep to the sternocleidomastoid

Depresses the hyoid bone and larynx

Innervated by the ansa cervicalis

Depressors Sternothyroid muscle

Depresses the thyroid cartilage

Originates from the sternum and first costal cartilage

Inserts into the oblique line of the thyroid cartilage

Innervated by fibers of the spinal nerves

Depressors Thyrohyoid muscle

Originates from the thyroid cartilage to the

Inserts into the inferior margin of the greater cornu of the hyoid bone

Depress the hyoid or raises the larynx

Innervated by the spinal nerve

Laryngeal StabilityStability is the key to control

Gained through the development of the infra and suprahyoid musculature

Larynx is intimately linked via the hyoid bone, to the tongue

Movement of the tongue is translated to the larynx

Vocal Fold ParalysisMost frequent cause- damage to the nerve during

thyroid surgery or carotid surgery, blunt trauma, CVA, or aneurysm

One side of the Recurrent Laryngeal Nerve is damaged (lower motor neuron)- unilateral vocal fold paralysis

Bilateral nerve damage=Bilateral paralysis

Adductor paralysis-muscles of adduction are paralyzed and vocal folds remain in the abducted position

Abductor paralysis-cannot abduct the folds, respiration is compromised

Vocal Fold ParalysisDamage to Superior Laryngeal nerve results in

inability to alter pitch

Unilateral paralysis- one vocal fold is still capable of motion and phonation can still occur but it will be breathy

Bilateral adductor paralysis results in virtually complete loss of phonation