Anatomy of larynx physiology, 29.08.16, dr.bakshi

[1] Organ for phonation

[2] Provides a protective sphincter at the inlet of the air passages :

Prevents the entry of swallowed food and other foreign bodies

Provides a blockade for generation of high intrathoracic pressure for coughing and aiding extreme muscular efforts

During the 4th week of IUL, the rudiment of the respiratory tree appears as a median laryngotracheal groove in the ventral wall of the pharynx.

The groove subsequently deepens and its edges fuse to form a septum, thus converting the groove into a splanchnopleuric laryngotrachealtube.

This process of fusion commences caudally and extends cranially but does not involve the cranial end where the edges remain separate, bounding a slit like aperture through which the tube opens into the pharynx.

The tube is lined with endoderm from which the epithelial lining of the respiratory tract is developed.

The cranial end of the tube forms the larynx and trachea, and the caudal end produces two lateral outgrowths from which the bronchi and right and left lung buds develop.

Extends from root of tongue to trachea.

Lies opposite to 3rd to 6th cervical vertebra in men - and at a higher level in children and women.

Male Female

Length 44 mm 36 mm

Transverse diameter 43 mm 41 mm

AP diameter 36 mm 26 mm

Made up of skeletal framework of cartilages, joints, ligaments and membranes.

Cavity of larynx is lined by mucous membrane which is continuous above and behind with that of the pharynx and below with that of the trachea.

1. Size - smaller in infants.

2. Shape - funnel shaped.

3. Softness - cartilages are softer.

4. Superiorly placed in infants.

5. Straighter and less oblique in infants.

6. Sensitivity - greater in infants.

7. Subglottis - very narrow.

9 cartilages :

3 unpaired: Thyroid cartilage

Cricoid cartilage

Epiglottis

3 paired : ArytenoidS

Corniculate (Cartilage of Santorini)

Cuneiform (Cartilage of Wrisberg)

THYROID CARTILAGE:

• Shield like.

• Largest of all the cartilages.

• Anteriorly 2 lamina - join together in the midline inferiorly but anteriorly they do not meet forming thyroid notch.

• Angle of fusion of lamina : 90 degrees in men

120 degrees in female

• Fused anterior borders form a projection called the laryngeal prominence (Adam’s apple)

• Posteriorly the lamina diverge.

Posterior border of each prolong to form 2 slender processes – superior and inferior cornua

1. Superior cornu : Long, narrow and curves upwards, backwards and medially.

- Lateral thyroid ligament is attached to this cornu.

2. Inferior cornu : short,thicker,curves downwards & medially.

- Articulates with cricoid cartilage.

Oblique line : Present on the external surface of each lamina, it extends from the superior thyroid tubercle to the inferior thyroid tubercle.

- Gives attachment to thyrohyoid, sternothyroid, inferior constrictors.

Superior border of each thyroid lamina gives attachment to corresponding half of thyrohyoid ligament.

Inferior border is divided to into halves on each side by inferior tubercle.

Cricothyroid membrane is attached to medial portion of inferior border.

CRICOID CARTILAGE:

Only complete cartilage.

Signet -ring shaped.

Forms most of the posterior part of larynx.

Posteriorly - broad lamina.

Anteriorly - narrow arch.

Articulates with inferior cornu of thyroid cartilage, near the junction of arch and lamina.

Lamina has articular facets for arytenoids.

Vertical ridge in midline of lamina gives attachment to longitudinal muscles of oesophagus.

Lined with mucous membrane over entire surface.

ARYTENOID CARTILAGE:

2 in number

Present on the upper and lateral borders of cricoidcartilage.

Irregular 3 sided pyramid.

2 processes:

Vocal process.

Muscular process.

.

-articulates with corniculate and gives attachment to the aryepiglottic folds.

.

Posterior surface - covered by transverse arytenoid.

Base - concave, smooth surface for articulation with cricoid.

Synovial joint.

Capsular ligament is loose, allowing both rotatory and medial and lateral gliding movements.

CORNICULATE CARTILAGE:

2 small, conical nodules.

Elastic fibrocartilage.

Synovial joint.

Situated in posterior part of aryepiglottic folds of mucosa.

CUNEIFORM CARTILAGE:

2 small, elongated flakes.

Elastic fibrocartilage.

Present ventral to the corniculate cartilage.

EPIGLOTTIS: Elastic fibrocartilage

Thin, leaf like

Projects upwards behind the tongue and body of hyoid.

Attached to thyroid cartilage by a narrow stalk just below the thyroid notch.

Sides of the epiglottis are attached to arytenoid cartilages by aryepiglottic folds.

Posterior surface of epiglottis is concave, smooth.

Anterior surface –free, covered with mucous membrane.

Mucous membrane is reflected onto pharyngeal part of tongue - median glossoepiglottic fold.

Also to lateral wall of pharynx - 2 lateral glossoepiglotticfolds

Depression between the two folds – Vallecula.

Hyoepiglottic ligament connects epiglottis to the hyoid bone in front.

The epiglottis is attached to the inner surface of the thyroid cartilage just below the thyroid notch by the thyroepiglottic ligament.

The space between the epiglottis and the thyrohyoid membrane is filled with fatty tissue and is called the pre-epiglottic space.

Calcification of laryngeal cartilages:

Corniculate, cuneiform, epiglottis and apices of arytenoids are elastic fibrocartilages - little tendency to calcify.

Thyroid, cricoid, greater part of arytenoids are hyaline cartilages - begin to calcify in late teens.

Thyroid calcification starts in inferior cornu.

Calcification of muscular process and body of arytenoids -4th decade.

Calcification of posterior part of cricoid lamina and posterior part of arytenoids – confused as foreign body radiologically.

LIGAMENTS:

Extrinsic ligaments : Thyrohyoid membrane.

Hyoepiglottic ligament.

Cricotracheal ligament.

Intrinsic ligaments : Quadrate membrane.

Cricovocal membrane.

THYROHYOID MEMBRANE: Joins thyroid cartilage and hyoid bone (greater

cornu and upper border of posterior surface of body of hyoid)

Fibroelastic tissue. Median and lateral parts are thickened. Median - Median thyrohyoid ligament. Lateral - Lateral thyrohyoid ligament - connects

superior cornu of thyroid to posterior end of greater cornu of hyoid.

Cartilago triticea - a small nodule in the ligaments. Membrane is pierced by

Internal branches of superior laryngeal nerveSuperior laryngeal vessels.

CRICOTRACHEAL LIGAMENT:

Connects lower border of cricoid with 1st tracheal ring.

HYOEPIGLOTTIC LIGAMENT:

Connects epiglottis to body of hyoid.

A fibroelastic membrane lying beneath the mucous membrane of larynx.

Divided into 2 parts by laryngeal ventricle.

Upper part : Quadrilateral membrane.

Lower part : Cricovocal ligament.

Quadrilateral membrane :

Extends from arytenoid to the epiglottis.

Upper border forms aryepiglottic fold.

Lower free border is thickened - vestibular ligament.

Cricovocal membrane:(conus elasticus)

Thick membrane.

Extends upwards and medially from the arch of cricoidcartilage.

Stretched between the midpoint of laryngeal prominence of thyroid cartilage anteriorly to the vocal process of arytenoid behind.

Free upper border - Vocal ligament.

Anteriorly thickened - Cricothyroid ligament.

CAVITY OF LARYNX

Starts at the inlet of larynx.

Ends at the lower border of cricoid.

Divided into 3 compartments by the ventricular and vocal folds :

1. Superior vestibule : above vestibular folds.

2. Ventricle : between vocal and vestibular folds.

3. Subglottic space : from vocal folds to lower border of cricoid.

A fissure between the vestibular folds : Rima vestibuli

A fissure between the vocal folds : Rima glottidis(glottis)

Laryngeal inlet:

Superiorly : Free edge of epiglottis.

On either side : Aryepiglottic folds.

Posteriorly : Mucous membrane between the two arytenoid cartilages.

2 thick pink folds of mucous membrane.

Enclose vestibular ligament.

In front - fixed to angle of thyroid cartilage below the attachment of epiglottic cartilage.

Behind - to anterolateral surface of arytenoid cartilage

over vocal process.

2 fold like structures. Extends from middle of angle of thyroid cartilage to

vocal process of arytenoids Made up of mucosa and muscle. The strict anatomical definition of the vocal cord is

that part of the free edge of the cord, covered by squamous epithelium, which has a vertical height of about 5mm, being bounded superiorly and inferiorly by the superior and inferior arcuate lines.

The free edge of the vocal cord is covered by squamous epithelium.

Its superior and inferior surfaces are covered by respiratory epithelium and the junction between the respiratory and squamous epithelium above and below is marked by the superior and inferior arcuate lines, respectively.

Mucosa consists of : Epithelium (stratified squamous)

Lamina propria :

-superficial layer

-intermediate layer

-deep layer

Superficial layer vibrates most significantly during phonation.

-Consists of loose fibrous tissue.

Intermediate layer - consists of elastic fibers.

Deep layer - collagenous fibers rich in fibroblasts.

Intermediate + deep layer Vocal ligament.

Anterior macula flava and posterior macula flava are present along the edge of vocal fold.

-serve as a cushion and protect the ends from mechanical damage caused by vocal fold vibrations

Vocal fold is a multilayered vibrator.

Mechanically divided into 3 layers:

1) Cover :

- Epithelium and superficial layer of lamina propia

2) Transition :

- Intermediate and deep layers of the lamina propia

3) Body :

- Vocalis muscle

Elongated fissure between vocal folds - anteriorlyand the - vocal processes and bases of arytenoids –posteriorly

Limited behind by mucous membrane between arytenoid cartilages with top portion of cricoid cartilage as its base.

3/5th of the length - Intermembranous part. Remainder lies between vocal processes-

Intercartilagenous part. Length of glottis : 23mm - Men.

16-17mm - Women.The glottis is said to consist of the vocal cords, the

space which lies in a horizontal plane 1 cm inferior to the level of the upper surface of the vocal cord, the anterior commissure and posterior commissure.

SUBGLOTTIS:

Lower part of laryngeal cavity.

From the level of vocal folds to the lower border of cricoid cartilage.

Upper part - elliptical.

Lower part - widens and becomes circular.

Lined with mucous membrane.

The subglottis can be divided into 2 parts.

The anterior fixed part is a triangle whose apex lies superiorly at the anterior commissure.

Here, the mucosa is tightly bound to the cartilage, which has foramina through which tumour can pass.

Extrinsic : Maintain position of larynx in neck.

Intrinsic : Regulate mechanical properties of vocal folds.

BELOW THE HYOID BONE:

ABOVE THE HYOID BONE:

1) Thyrohyoid

2) Sternohyoid

3) Sternothyroid

4) Omohyoid.

1) Mylohyoid2) Geniohyoid3) Stylohyoid

4) Stylopharyngeus

5) Palatopharyngeus

6) Salpingopharyngeus.

CRICOTHYROID:

Origin:

- Lower border and lateral surface of cricoid cartilage.

Insertion:

- Lower border of thyroid cartilage.

- Inferior cornu

Actions:

- Rotates cricoid cartilage about a horizontal axis.

- Lengthens the vocal folds by increasing the distance between the angle of thyroid cartilage and arytenoids.

POSTERIOR CRICOARYTENOID:

Origin:

- Posterior surface of lamina of cricoid cartilage.

Insertion:

- Posterior aspect of muscular process of arytenoidcartilage.

Actions:

- Opens the glottis.

- Abductor of vocal cord.

LATERAL CRICOARYTENOID:

Origin:

- Lateral part of upper border of arch of cricoid cartilage.

Insertion:

- Front of muscular process of arytenoids.

Actions:

- Adducts the vocal process.

- Vocal fold - adducted, elongated, thinned.

TRANSVERSE ARYTENOID:

Origin:

- Posterior surface of muscular process of arytenoid.

Insertion:

- Similar place on the other arytenoid.

Actions:

- Adductor of vocal cord.

OBLIQUE ARYTENOID:

Origin:

- Posterior aspect of muscular process of one arytenoid.

Insertion

- Apex of other arytenoid.

- Few fibers prolong into aryepiglottic fold

Actions:

- Adducts the vocal fold(inter cartilagenouspart)

THYROARYTENOID (Vocalis) :

Origin:

-posterior aspect of angle of thyroid cartilage.

-adjacent part of cricothyroid ligament.

Insertion:

vocal process

-anterolateral surface of cartilage.

- Fibres of the thyroarytenoid are prolonged into the aryepiglottic fol, some continuing to the margin of the epiglottis as the thyroepiglotticus.

Actions:

1) Thyroepiglotticus - widens the inlet of larynx

2) Vocalis - tensor of vocal cord

Muscles which abduct vocal fold:

Only posterior cricoarytenoid.

Muscles which adduct vocal cord:

1) Lateral cricoarytenoid.

2) Interarytenoid.

3) Thyroarytenoid.

Muscles which tense vocal cord:

- Vocalis.

Closers of inlet of larynx:

1) Aryepiglotticus.

2) Oblique arytenoids.

MOVEMENTS OF VOCAL FOLDS

Affect the shape and size of rima glottidis.

1. During quiet breathing:(rest)

- intermembranous part of cord is triangular.

- intercartilagenous part is quadrangular.

2. During phonation or speech:

- intermembranous and intercartilagenous parts are reduced to a linear chink by adduction of vocal folds and adduction and medial rotation of arytenoidcartilages.

3. During forced inspiration:

- vocal fords undergo extreme abduction.

- rima are triangular.

- arytenoids rotated laterally and vocal process move widely apart.

4. During whispering:

- intermembranous part is closed.

- intercartilagenous part is opened.

Mucous glands are freely distributed throughout.

Mucous glands are numerous over the posterior surface of epiglottis, margins of lower part of aryepiglottic fold and saccule.

Vocal folds are devoid of glands.

The mucous membrane is lubricated by the glands within the saccules.

The squamous epithelium covering the vocal folds is therefore susceptible to dessication.

1. Laryngeal branches of superior and inferior thyroid

arteries.

2. Cricothyroid branch of superior thyroid artery.

Superior thyroid artery arises from ECA

Inferior thyroid artery arises from Thyrocervicaltrunk of first part of subclavian artery.

Superior vessels enter internal jugular vein by way of superior thyroid or facial vein.

Inferior vessels drain into brachiocephalic veins by way of inferior thyroid vein.

Some venous drainage from the larynx is by way of the middle thyroid vein into the internal jugular vein.

Separated by vocal folds into : (1) Upper group

(2) Lower group

Upper group - upper deep cervical lymph nodes.

Lower group - lower part of deep cervical chain.

The supraglottic portion of the larynx is derived from the buccopharyngeal anlage(arches III and IV), whereas the glottic and subglottic portions derive from pulmonary anlage (arch VI).

Thus, each major component has an independent lymphatic circulation, separated into an upper and a lower drainage system.

A vocal fold contains only a few capillary vessels.

It is this poverty of lymph drainage which predisposes Reinke’s space to accumulation of oedema.

From vagus by way of

(i) superior laryngeal nerve

(ii) recurrent laryngeal nerve.

SUPERIOR LARYNGEAL NERVE:

Arises from inferior ganglion of vagus.

Receives a branch from superior cervical sympathetic ganglion.

Descends lateral to pharynx,behind the internal carotid artery.

At the level of greater horn of hyoid

small external branch large internal branch.

supplies motor branch pierces thyrohyoid membrane

cricothyroid muscle sensory somatosensory

[3] REINKE’S SPACE

It lies immediately beneath the laryngeal mucosa, i.e superficial to the vocal ligament

It is bounded superiorly and inferiorly by the junction of the columnar and squamousepithelium which represents the superior and inferior arcuate lines.

PHYSIOLOGY OF LARYNX

PROTECTION OF AIRWAY

ROLE IN DEGLUTTION

ROLE IN RESPIRATION

INVOLUNTARY REFLEXES

FIXATION OF CHEST

PHONATION

LARYNX ACTS AS SPHINCTER AT INLET OF AIRWAYAT SAME TIME IT MAINTAINS A PATENT AIRWAY DURING INSPIRATION SUSTAINING A GREAT –VE PRESSURESO IT IS FORMED OF A RIGID CARTILAGENOUS FRAMEWORK WITH MOBILE PARTS TO PROVIDE BOTH ACTIONS

RECEPTORS:THERMO & CHEMORECEPTOR MOST DENSE IN SUPRAGLOTTIS

AFFERENT:INTERNAL LARYNGEAL NERVE EFFERENT:VAGUS NERVE

LARYNGOSPASM CAN OCCUR IN SUSCEPTIBLE PEOPLE

THIS REFLEX IS WEAK IN INFANTS & STRENTH INCREASE WITH MATURATION & MYELINATION COINCIDING WITH INCIDENCE OF SIDS

ANTERIOR AND UPWARD MOVEMENT OF LARYNX

DIRECTS FOOD TOWARDS HYPOPHARYNX

RELAXES UES AT END OF PHARYNGEAL PHASE

BEST ADAPTED FOR REGULATING AIRWAY

WIDENING OF GLOTTIS DURING INSPIRATION IS A PRIMARY ACTION OF VENTILATION

PCA THE ONLY DIALATOR, CONTRACTS EVEN BEFORE THAT OF DIAPHRAGM

PCA ACTIVITY VARIES WITH BREATHING

LARYNX DENSELY SUPPLIED WITH SENSORY RECEPTORS

THERMORECEPTORS

CHEMORECEPTORS

PROPRIORECEPTORS

DIRECT EFFECT ON BLOOD PRESSURE: HYPERTENSION

DIRECT AFFECT ON HEART: BRADYCARDIA

CONTRACTION OF EXTRINSIC LARYNGEAL MUSCLES FIXES CHEST DURING CLIMBING AND OTHER STRENOUS EXERCISES.

PHONATION: GLOTTIS / PRODUCTION OF VOICE

RESONANCE: SUPRAGLOTTIS, PHARYNX, NOSE, CHEST / MODULATION OF VOICE

ARTICULATION: TONGUE, PALATE, LIPS / SHAPING INTO WORDS

5 PRE-REQUISITES:

ADEQUATE BREATH SUPPORT

APPROXIMATION OF VOCAL FOLDS

FAVOURABLE VIBRATORY PROPERTIES

FAVOURABLE VOCAL FOLD SHAPE

CONTROL OF LENGTH AND TENSION

BODY-COVER CONCEPT

VIBRATORY CAPACITY OF VC:

PHYSICAL PROPERTIES ARE CRUCIAL

MUCOSA FREELY UNDULATES OVER UNDERLYING VOCAL LIGAMENT

MOST SUPERFICIAL LAYER OF LAMINA PROPRIA (REINKE’S SPACE) ACTS AS SHOCK ABSORBER

HIGH SPEED PHOTOGRAPHY

STROBOSCOPY

ELECTROGLOTTOGRAPHY

ECHOGLOTTOGRAPHY

ELECTROMYOGRAPHY

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