A NATOMY AND PHYSIOLOGY OF THE L ARYNX February 3, 2014.

ANATOMY AND PHYSIOLOGY OF THE LARYNXFebruary 3, 2014

WHY DO WE NEED TO KNOW THE ANATOMY AND PHYSIOLOGY OF THE LARYNX

A solid understanding of normal structure and function of the larynx basis for Evaluating larynx and phonatory function Impact of specific pathologies Interpretation of evaluation findings Development of appropriate voice treatment

plans

LARYNX

Larynx (http://www.youtube.com/watch?v=Or5vGSLvoiE&feature=fvsr), (http://www.youtube.com/watch?v=DfN5J0-WbzM&feature=relmfu) http://www.youtube.com/watch?v=jlgUbA2ozNY

http://www.youtube.com/watch?v=TiCgex4dBH4

http://www.youtube.com/watch?v=Or5vGSLvoiE&feature=fvsr

http://www.youtube.com/watch?v=Or5vGSLvoiE&feature=fvsr

http://www.youtube.com/watch?v=DfN5J0-WbzM&feature=relmfu

http://www.youtube.com/watch?v=DfN5J0-WbzM&feature=relmfu

http://www.youtube.com/watch?v=jlgUbA2ozNY

http://www.youtube.com/watch?v=jlgUbA2ozNY



LARYNX

Cartilaginous tube Connects to the respiratory system (trachea and lungs)

inferiorly Superiorly to the vocal tract and oral cavity Position important because of its relationship and

integration between three subsystems Pulmonary power house Laryngeal valve Supraglottic vocal tract resonator

Lungs are the power supply for aerodynamic (subglottic tracheal) pressure that blows vocal cords apart – sets them into vibration

Vocal cords oscillate in a series of compressions and rarefactions

Modulate the subglottic pressure or transglottal pressure of short pulses of sound energy to produce human voice

LARYNGEAL VALVE Complex arrangement of muscles, mucous

membrane, and connective tissue Soft tissues responsible for airway

preservation Cartilage serves as a protective shield Muscles and cartilages create three levels of

folds or sphincters for communication and vegetative body functionsEpiglottis folds posteriorly and inferiorly

over the laryngeal vestibule – separates the pharynx from the larynx – first line of defense for preserving the airway

LARYNGEAL VALVE

Second sphincter is formed by the ventricular folds (not active during phonation) become active during hyper function or effortful speech production and extreme vegetative closureCause increase in intra-thoracic pressure by blocking outflow of air from lungs

Tight compression with rapid contraction of the thoracic muscles during sneezing and coughing

Longer durations to stabilize the thorax during physical tasks (e.g., lifting, childbirth, defecation, etc.)

LARYNGEAL VALVE

Third and final layer is the true vocal cords Vibration for speech productionClose tightly for non-speech and vegetative tasks such as coughing, throat clearing and grunting

Angles of closure are multidimensional Horizontal (lateral to medial)Vertical

STRUCTURAL SUPPORT FOR THE LARYNX

Larynx is suspended from a single bone – hyoid or superior border

Six laryngeal cartilages Three unpaired (epiglottis, thyroid and cricoid) Three paired (arytenoid, corniculate, cuneiform)

Hyoid bone articulates with the superior cornu of the thyroid cartilage via the thyrohyoid membrane

Epiglottis cartilage – leaf shaped- attached to the inner portion of the anterior rim of the thyroid cartilage

Made up of elastic cartilage - does not ossify or harden with age – remains flexible to allow a pliable free edge to assist in closing airway and diverting foods and liquids towards the esophagus

STRUCTURAL SUPPORT FOR THE LARYNX Thyroid cartilage – three sided, saddle shaped curve Anterior attachment of the true vocal cords at the

internal rim of the anterior curve Posteriorly are two cornu or horns that extend

upward to articulate with the hyoid bone and inferiorly to articulate with cricoid cartilage

Made up of hyaline cartilage that ossifies – limits flexibility with age

Lateral walls form quadrilateral plates or laminae – meet in the midline in a thyroid notch or prominence

In newborns, the laminae form a curve of 130 degrees – angle becomes more acute with age

A fully matured thyroid cartilage is 90 degrees in males (Adam’s apple) and 110 degrees in females

STRUCTURAL SUPPORT FOR THE LARYNX Cricoid cartilage – hyaline cartilage – below the thyroid Signet ring shaped – narrow anterior curve and broad

posterior back Two sets of paired facets (flat surfaces) that articulate with

adjacent thyroid and arytenoid cartilages The cricothyroid joint connects the lateral edges of the

cricoid to the inferior cornu of the thyroid Cricothyroid joints are positioned on the top of the

posterior cricoid rim Both joints are lined with a synovial membrane (or

connective tissue cushion for the joint, supplies secretions for lubrication, blood supply, adipose cells and lymph tissue)

Do not display age related deterioration and gender differences

Inferior to the cricoid cartilage are the tracheal rings

STRUCTURAL SUPPORT FOR THE LARYNX Arytenoid cartilages are pyramidal in shape Four surfaces – anterior, lateral, medial and a base Anterior angle projects forward at the base forming the

vocal process Hyaline cartilage except for vocal process which is made

up of elastin Vocal process is the cartilaginous portion of the vocal

folds Lateral arytenoid angle is the muscular process – intrinsic

muscles for abducting and adducting the vocal folds Medial angle faces its arytenoid pair forms an even

surface for midline glottic closure Base is concave to allow smooth articulation with the

humped (convex) surface of the posterior cricoid cartilage (half cylinder over a bar)


Cricoarytenoid joint – two basic motions Rocks anteriorly and posteriorly over the cricoid

surface It also slides laterally Causes adduction, abduction and stabilizes the

vocal folds Vocal process tips can be pulled medially or

laterally to determine the size and shape of the glottis

Tips directed medially causes the vocal folds to meet in midline and close or adduct

When the vocal process tips are pointed laterally the vocal folds are drawn open and abduction occurs


Corniculate cartilages (cartilages of Santorini) are attached by a synovial joint to the superior tip of the arytenoids

The cuneiform cartilages (cartilages of Wrisberg) are embedded in the muscular complex superior to the corniculates

Hyaline cartilages Add structure and stability to preserve the

airway

EXTRINSIC AND INTRINSIC MUSCLES Extrinsic laryngeal muscles - attached to a site on the

larynx and an external point (hyoid bone, sternum, mandible or skull base)

Major function – to change the height and tension as a gross unit (swallowing, lifting, phonating and other vegetative acts)

Also alter the shape and filtering characteristic of the supraglottic vocal tract – modifies vocal pitch, loudness and quality

Intrinsic muscles – both ends attached within the larynx Primary function – alter shape and configuration of the glottis

to modify the position, tension and edge of the vocal folds Adduction (closing), abduction (opening) and modifying vocal

fold length, tension and thickness Both sets of muscles also help with ventilation, airway

protection, communication and laryngeal valving

EXTRINSIC LARYNGEAL MUSCLES Suprahyoid (above the hyoid bone) and infrahyoid (below the

hyoid bone) Identified based on their names which describe their anatomical

attachments Knowing the attachments one can predict the effect of the

individual muscle contraction (shortening) between the sites Stylohyoid (styloid process of the temporal bone to the hyoid bone) -

raises the hyoid bone posteriorly Mylohyoid (mandible to the hyoid bone) – raises the hyoid bone

anteriorly Digastric anterior belly (mandible to the hyoid) – raises the hyoid bone

anteriorly Digastric posterior belly (mastoid process of the temporal bone to the

hyoid) – raises the hyoid bone posteriorly Geniohyoid (mandible to the hyoid) – raises the hyoid bone anteriorly

Raises the larynx during swallowing to protect airway Laryngeal elevation during phonation is a sign of excessive

extrinsic laryngeal muscle tension and a sign of hyperfunctional voice use

EXTRINSIC MUSCLES OF THE LARYNX

Infrahyoid muscles Sternohyoid (sternum to hyoid bone) – lowers the

hyoid bone Sternothyroid (sternum to thyroid cartilage) –

lowers the thyroid cartilage Omohyoid (scapula to the hyoid cartilage) –

lowers the hyoid bone Thyrohyoid (thyroid cartilage to the hyoid bone)

– shortens the distance between the thyroid and hyoid bone

Sternocleidomastoid (forms a sheath between the mastoid process and the sternum)

Lower the larynx in the neck

EXTRINSIC LARYNGEAL MUSCLES

INTRINSIC LARYNGEAL MUSCLES

5 intrinsic muscles attaches to cartilages to modify the cricothyroid and cricoarytenoid joint relationships Affect the position, length and tension of the

vocal folds Changing the position of the cartilage framework

that house the vocal folds Altering the shape and configuration of the

glottis, the opening between the vocal folds


Cricothyroid – broad, fan-shaped muscle – inferiorly to the cricoid cartilage and superiorly to the thyroid cartilage – decreases the distance between the two cartilages – lengthening the vocal cords Pars recta (vertical belly) Pars oblique (angled belly)

Reduces the vibrating mass of the vocal folds by increasing the longitudinal tension, limits the vibrations to the thinnest portion of the vocal fold located at the medial edge

Greatest contributor to the fundamental frequency control – higher tones

INTRINSIC LARYNGEAL MUSCLES Thyroarytenoid – attached anteriorly to the internal

angle of the thyroid cartilage and posteriorly to the vocal process of the arytenoid

Two compartments Thyromuscularis lateral component – adduction of the vocal

cords – fast acting muscle fibers Thyrovocalis (vocalis) medial component – greater control

over phonation – slow acting muscle fibers Body of the vocal fold – contraction shortens the fold

length by pulling the arytenoid cartilages anteriorly and thickens the vocal cords by increasing the mass of the vibrating medial edge

Lowers the fundamental frequency, increases loudness and tightens the glottic closure

Control over the vocal fold shape and edge and glottic closure patterns

INTRINSIC LARYNGEAL MUSCLES Lateral cricoarytenoid muscle – broad fan-shaped

muscle – lateral side of the cricoid to the arytenoid muscular process Rocks the arytenoids anteriorly and slides them laterally Redirects the vocal process medially brings the

membranous vocal folds to midline or adduction Strongest vocal fold adductors

Interarytenoid muscles – two bellies Transverse portion (only unpaired intrinsic laryngeal

muscle) attaches to the posterior plane of each arytenoid Oblique portion (crossed bellies) attached at a 45 degree

angle from the inferior border of one arytenoid to the superior border of its contralateral pair

Shortens the distance between the arytenoid cartilages causing adduction – forceful closure of the posterior glottis


Posterior cricoarytenoid – sole abductor of the vocal folds

Posterior lamina of the cricoid and the muscular (lateral) arytenoid cartilage

Contraction causes abduction (opens) the vocal folds

When the arytenoids rock posteriorly to redirect the vocal processes laterally and separate the membranous portions of the vocal folds

Abducts for respiration and quick glottal opening gestures during unvoiced sound productions


Exceptional rules All muscles are paired (right with a left) except

for the transverse interarytenoid which functions as one unit, bringing the arytenoid cartilages together

All intrinsic muscles server as adductors except for posterior cricoidarytenoid muscles or the sole abductor

All muscles are innervated by the recurrent laryngeal nerve except the cricothyroid which is innervated by the external branch of the superior laryngeal nerve

VOCAL CORD MICROSTRUCTURE

Membranous portion of the vocal folds – 5 histologically discrete layers – vary in composition and mechanical properties

Membrane oscillates to create sound Integrity of the vibration pattern for

phonation relies on the pliable elastic structure

Different layers provide variable amounts of flexibility and stability


5 layers are epithelium, 3 layers of the lamina propria (superficial, intermediate and deep) layers, and the vocalis muscleEpithelium – mucosal covering of

stratified squamous cells that wraps over the internal contents, thinnest layer, consists of 6-8 cell layers, described as a pliable capsule – needs a thin layer of slippery mucous lubrication to oscillate

VOCAL CORD MICROSTRUCTURE Next 3 layers form the lamina propria

Loose extracellular tissue (extracellular matrix) composed of lipids, carbohydrates and specialized proteins

The lamina is slightly more dense than the epithelium but still flexible and loose

Superficial layer or Reinke’s space is a gelatinlike soft, slippery substance which allows it to vibrate significantly during phonation which is violated by vocal cord pathology, forceful abduction

Intermediate layer is composed principally of elastic fibers which can stretch to twice its length


Deep layer of the lamina propria is still denser and composed of collagen fibers

Tissues of the third and fourth layers form the vocal ligament-not present in the new born – appears between 1-4 years and continues to develop until maturity at puberty

Deep layer is interspersed by muscle fibers to join vocalis muscle and the deep layers together


The fifth layer or the vocalis muscle forms main body of the vocal fold Provides tonicity, stability and massIt is the only true “active” tissue and is the only portion of the vocal cord that can contract and relax in response to neurologic control

The lamina propria and epithelium layers vibrate passively in response to aerodynamic breath support


Extracellular matrix of the lamina propriaComposed of fibrous proteins,

interstitial proteins, carbohydrates and lipids

Fibrous proteins consists of elastin and collagen found in different concentration in different layers of the lamina and contributes to the vibratory properties of the vocal fold cover


Elastin fibers predominate in the superficial and intermediate layers, collagen in the deep layer

Elastin lets the layers stretch and then return to its original shape

Collagen does not stretch easily but tolerates stress but offers strength to the extracellular matrix


Interstitial proteins Consists of proteoglycens and glycoproteins

Role in vocal cord vibration is related to control of tissue viscosity, layer thickness and internal fluid content

Hyaluronic acid appears in greater concentration in the intermediate layer

Attracts water to form large, space filling molecules that creates a gel – acts as a cushion and resists compressive and shearing forces during vibration


Also protects cells from deterioration, assists in tissue repair and clotting

Exceeds in males to females (3:1) Glycoproteins, lipids and

carbohydrates Consists of fibronectin found in normal and injured vocal cords – plays a role in wound healing


Body cover theory of vocal fold vibration (Hirano)Three vibratory divisions

Cover (epithelium and superficial layer of the lamina propria)

Transition (intermediate and deep layer of the lamina propria)

Body (vocalis muscle)


The vibrating cover forms the compliant, fluid oscillation seen in the vocal vibratory patterns while the body provides stiffer underlying stability of the vocal fold mass and tonus

The transition serves as coupling between the superficial mucosa and the deep muscle tissue of the vocal folds during vibration

Undulation or oscillation of the superficial vocal fold layers creates a ripple of tissue deformation and recoil


Three vibratory phases of wave motion seen in endoscopyHorizontal (medial to lateral movements) as seen in the open and closing patterns of vibration – 1-2 mm

Longitudinal (anterior and posterior – zipperlike wave) seen in front-to-back travelling wave 3-5 mm

Vertical phase (inferior to superior opening and closing of the vocal folds) as seen in an upper versus lower lip differences – mostly unseen

FOLDS AND CAVITIES OF THE LARYNX

Major folds are true vocal folds Superior and lateral to the true folds are the

false or ventricular folds Do not actually vibrate in normal voice

production except at very low fundamental frequency (below 50 Hz)

Few muscle fibers – very difficult to regulate their tension, mass and length

Aryepiglottic folds form a sphincter enclosing the entrance to the larynx

During swallowing and protective acts these folds contract to reduce the diameter of the laryngeal entrance to protect the airway


Supraglottal cavity Lies above the vocal folds Superior border is the aryepiglottic sphincter Acts as a resonator of the sound produced by the

vocal cords Subglottal cavity

Lies beneath the vocal folds Lower boundary is the first tracheal ring Pressure increases beneath the closed vocal

folds until it becomes sufficient to force the folds open and begin phonation


Ventricles Paired cavities lying above and

slightly lateral to the true vocal cords

Opening is very small and little effect on the sound produced

However in some conditions of singing the opening is sufficient to permit meaningful resonance adding to the glottal tone

DEVELOPMENTAL CHANGES

Newborns the larynx is situated high in the neck – cricoid positioned at the level of C3 to C4

Newborns breathe only through nasal passages in the first few months of life allowing them to breathe and swallow simultaneously

During the first year the larynx begins its descent in the neck as the pharynx lengthens and widens

By puberty the larynx is at the level of C6 or C7 Accompanied by skeletal facial growth and

development, creates an expanded vocal tract which contributes a drop in fundamental frequency

DEVELOPMENTAL CHANGES Intrinsic larynx also undergoes dramatic changes from

birth through puberty Vocal fold length of boys and girls is similar until 10

years Gradual and consistent gender development changes

vocal cord length and ratio between membranous to cartilaginous portions of the vocal cords

In males with the rise in testosterone at puberty stimulates the anterior growth of the thyroid notch and wide growth of the pharynx

In newborns have no vocal ligament (intermediate and deep layers of the lamina propria) and therefore little stability, the greater ratio of cartilage to membrane length provides protection of the airway (vocal ligament emerges between 1-4 years)

DEVELOPMENTAL CHANGES

GERIATRIC VOCAL FOLD

Deterioration in voice quality, pitch and loudness range and endurance among geriatric speakers

Common appearance of thinned (bowed) vocal folds in elderly patients with no other pathology except advanced chronological age

Described by the term “presbylaryngeus” Intermediate layer of the geriatric vocal folds

was observed to be looser and thinner causing loss of tissue bulk, resulting in bowed appearance

Studies confirm that the lamina propria decreases in flexibility and elasticity with age due to increased cross-linking of fibers

PHYSIOLOGY OF PHONATION Theory of vibration

Based on physical process of flow-induced oscillation A consistent stream of air flows past the tissues creating a

repeated pattern of opening and closing Van den Berg’s aerodynamic myoelastic theory

At the onset of phonation, subglottal pressure rises as expiratory forces are met by resistance from the adducted vocal folds

When the pressure rises to overcome the resistance the folds are blown and subglottal pressure diminishes creating an increase in flow through the glottis

Because air pressure and flow are inversely proportional, when flow increases, air pressure decreases between the vocal folds (Bernoulli Principle)

The elastic tissue recoil pulls the vocal cords back toward midline completing the cycle of vibration

PHYSIOLOGY OF PHONATION Self oscillating system by Titze

Respiration is the driving force that sets the vocal folds in motion and kept in motion as follows: In the subglottal region the leading edge of the

vocal folds are blown apart and set into motion by subglottic pressure and translaryngeal (glottal flow) is positive

Intraglottal space or the small space directly between the vocal folds – intraglottal pressure keeps the vocal folds oscillating by alternating exchange of airflow and pressure peaks – when the vocal cords close the pressure is negative but rises as the air flow is cut off by the closing glottis

PHYSIOLOGY OF PHONATION

Supraglottal air column located at the outlet of the glottis immediately above the vocal folds – air molecules are compressed or rarified in a delayed response to the alternate pressure and flow puffs modulated by the vibrating vocal folds (molecules are pushed and released in response to the sound energy pulses released from the oscillating vocal folds) causing transfer of energy from the fluid or air pressure to the tissue or upper lip of the vocal folds and assists in sustaining the oscillation

MECHANISM OF VOCAL FREQUENCY CHANGE

The physical properties that determine the frequency of a vibrating string also determine the vibrating frequency of the vocal cords

Determined by length, tension and mass Total mass is not important but the mass

vibrating is more important Amount of mass set into vibration depends

upon fundamental frequency, intensity and mode of vibration and length of the vocal cord

As the band is stretched, the thickness of the band decreases

VOCAL FOLD LENGTH AND FUNDAMENTAL FREQUENCY Three voice register with respect to pitch

Pulse register or glottal fry Modal register Falsetto

In the pulse register vocal folds are closed 90% of the cycle (60Hz)

In the modal register, as the vocal length increases, frequency increases

Vocal cords are closed 50% of the time In the falsetto or upper register the fundamental frequency

appears to decrease as vocal fold length is increased Opposite to that predicted by that of a vibrating string The vocal cords also do not seem to adduct completely

during phonation Length is not the sole mechanism of fundamental

frequency

VOCAL FOLD TENSION AND FUNDAMENTAL FREQUENCY As tension increases the frequency increases (similar to

that of a string) Difficult to measure tension Indirect evidence must be obtained Largest variations occur in the upper frequencies or in

the falsetto register Very little variation in the frequencies heard in speech Tension is not the only determinant but mass per unit

length has a pronounced influence on the fundamental frequency of vibration

In the modal register the mass is an important factor however, in the falsetto register, tension is a determinant factor

Mass per unit length more important than just tension or mass

VOCAL FOLD MASS AND FUNDAMENTAL FREQUENCY

Vocal frequency decreases as mass increases (similarly to the vibrating string)

FREQUENCY AND AIR FLOW

Airflow is another contributing factor – sign of an inefficient system

The speed of the airflow also causes variations in frequencies in voice production

However excessive airflow makes the system inefficient resulting in breathiness

All three factors important in voice production Mass Tension Air flow

MECHANISM OF LOUDNESS CHANGE

Wide range of vocal intensities (exceeding 60 dB) Additional changes of intensity result from

variation in the size and shape of the vocal tract which acts as a resonator

Combination of airflows and pressure Increased pressures below the vocal folds when

released by the folds would produce a greater intensity

Controlling mechanism of vocal intensity is not subglottal air pressure rather it is degree and time of closure of the vocal folds

Maintaining closure of the vocal folds there is more time to build up pressure beneath them

MECHANISM OF LOUDNESS CHANGE More intense sound results when the subglottal air

pressure is sufficient to overcome the resistance of the vocal folds

The more vocal fold resistance there is to opening the greater the pressure disturbance when the resistance is overcome and folds are forced to open

Intensity is often controlled by the vocal folds through variation of glottal resistance (which is ratio of the pressure divided by the airflow)

Glottal resistance is a major controlling factor in the lower frequencies

At higher frequencies (in the falsetto range) airflow becomes a major variable

Very little variation of intensity in the falsetto range


Intensity is also dependent upon velocity of closure of the vocal folds

Glottal power is directly related to the rate of change of the airflow pulse at the moment of the closure

This rate of change of airflow is called airflow closing slope (page 395)

Steeper the slope the greater the increase in frequency

Intensity control therefore depends upon two factors – glottal resistance and rate of airflow change at the moment of closure


In an attempt to speak at a normal vocal intensity, patients increase air pressure by increasing the expiratory force from the thorax-abdomen system

The patient may attempt to increase glottal closure in an effort to increase glottal resistance and to maintain an adequate level of tension in the vocal folds

These increase in muscle activity causes vocal fatigue as well as excessive air rushing across the vocal folds (causing an increase in noise levels)

Vicious cycle ensues, vocal fatigue results in poorer vocal fold adduction and the greater need for even greater effort on the patient’s part leading to poorer voice

MECHANISMS OF LOUDNESS CHANGE

Variation of the frequency composition of a tone also varies its intensity

Adding frequencies or varying the amplitude of the components of the tone affects the intensity of the complex tone

Spectrum of the vocal folds can be varied (within limits) and thus alter the overall intensity of the vocal fold tone

Speed of closure affects the spectral features of the glottal tone

Number of frequency components in the pathological voice is smaller than in the normal voice

MECHANISMS OF LOUDNESS CHANGE

Lower intensities are used to compensate for the different spectral characteristics and their effect on intensity

A patient may also try to increase subglottal pressues or adductory forces – results in an increase in strain and abuse to the vocal folds

Loudness is the perceptual correlate of intensity but intensity is not the only factor that affects loudness Pitch of the voice and its spectral composition also

affects perceived loudness Other factors include distance from the speaker,

room acoustics, interference at may affect the loudness of a voice as perceived by a listener

MECHANISM OF QUALITY VARIATION Identifies an individual and sets him or her apart

from another Spectrum determines voice quality It refers to number and amplitude of the frequencies

present in a complex tone (vocal fold tone) Vocal fold produces many different vocal qualities

each with its own spectral characteristics Shape and configuration of the vocal tract (length,

cross-sectional area, ratio of oral to pharyngeal cavity size, etc.) determine the voice quality

Physiological changes in laryngeal and vocal tract configuration produce different voice qualities

Change in voice quality can signal benign or a life threatening condition

NEUROANATOMY OF THE VOCAL MECHANISM

Volitional control rests in the brain Many points in the cortex, subcortical areas,

midbrain, and medulla play an important role in the ultimate control of phonation

Cerebral cortex responsible for conceptualization, planning and execution of speech act including phonation

3 major areas of cortex responsible for vocalization Precentral and postcentral gyrus (Rolandic area) Anterior (Broca’s) area Supplementary motor area


Speech can be initiated, stopped, slurred or distorted

Result of stimulation in the dominant or non-dominant hemisphere

Control of the motor acts occur in the cortex, individual muscle control occurs at a much lower level


Subcortical mechanismsMotor cortex has numerous

connections to the thalamus, metathalamus, hypothalamus, epithalamus, and subthalamus

Thalamus has numerous connections to the cerebellum and midbrain

Ventral lateral nucleus of the thalamus was responsible for initiating speech movements, control of loudness, pitch, rate and articulation


Thalamus acts as not only a relay station but is also involved in maintenance of consciousness, alertness, attention and integration of emotion into the speech act

Thalamus also integrates sensory information, coordinating outgoing information from the cortex and other areas of the brain and adding the emotionality to speech and voice


Midbrain structures Structures that connect the cerebrum with the

brainstem and spinal cord Four rounded areas called colliculi on the

posterior surface Superior colliculi assoicated with vision Inferior colliculi concerned with audition Stimulation of the cavity or cerebral aqueduct of

Sylvius and grey matter dorsal to the aqueduct or periaqueductal gray (PAG) produces activity in the laryngeal muscles

Lesions in this area also causes mutism Control muscles of respiration, vocalization and

orofacial region


Brainstem Nucleus ambiguus, nucleus tractus solitarii,

reticular formation have connections to the motor roots of the vagus and the PAG area

Neurons in this area responsible for control of respiration

Cerebellum Control and planning stages of a movement Without this control the cerebral cortex could not

function and would be ineffective Acts to regulate motor movement continuously

and regularly Coordinates muscles of the larynx

PERIPHERAL CONNECTIONS: THE VAGUS NERVE

Vagus provides sensory and motor fibers Start in the caudal portions of the nucleus

ambiguus Vagus emerges from the surface of the

medulla between the cerebellar penduncle and the inferior olives in the midbrain and exist the skull through the jugular foramen

After exiting the skull, the vagus divides into many branches that serves the head, neck, thorax and abdomen


After exiting a small filament or the meningeal filament exits the nerve to serve the Dura mater on the posterior fossa of the base of the skull

The auricular branch provides sensory fibers to the skin behind the pina and to the posterior par of the external auditory meatus

The pharyngeal branch provides motor fibers to the muscles of the pharynx and the soft palate


The major portions of the vagus serving the larynx are the superior laryngeal and recurrent laryngeal nerves

Superior laryngeal – primary sensory nerve – arises from the inferior ganglion of the vagus and descends along the side of the pharynx behind the internal carotid artery where it sends off two branches

The external branch descends along the side of the larynx to serve the cricothyroid muscle

The internal branch descends to an opening in the thyrohyoid membrane and enters the larynx to serve the mucous membrane of the larynx down to the true vocal folds, big SENSORY


The recurrent laryngeal nerve follows a different course on either side of the body

On the right side the recurrent descends in the neck to loop around the subclavian artery (just below the clavicle) and then ascends alongside the trachea to serve the remaining intrinsic muscles of the larynx

On the left side the recurrent laryngeal nerve takes a more circuitous route

Descends into the thorax, loops around the aorta and then ascends alongside the trachea until it reaches the larynx

It provides motor fibers to the remaining intrinsic laryngeal muscles

PERIPHERAL CONNECTIONS

The extrinsic muscles of the larynx are innervated by several nerves Anterior belly of the digastric – mylohoid branch

of the inferior alveolar nerve Posterior belly of the digastric – 7th cranial nerve

(facial) Mylohyoid muscle – mylohyoid branch of the

inferior alveolar nerve Geniohyoid, sternohyoid, sternothyroid, and

omohyoid by the ansa cerivcalis

PERIPHERAL CONNECTIONS

Protective reflexes of the larynx used to protect the airway and sustain life Sensory endings collect information from larynx

and respiratory system Transmit this information through reflexes arcs

and directly to the CNS Responds to changes in mechanical forces and

air pressure Send information to the CNS as well as to the

joints of cartilages that discharge Affect the electrical activity of some intrinsic

laryngeal muscles Stretch receptors in the muscles also discharge

when the muscle is stretched or contracts

A NATOMY AND PHYSIOLOGY OF THE L ARYNX February 3, 2014.

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Transcript of A NATOMY AND PHYSIOLOGY OF THE L ARYNX February 3, 2014.