Anatomy of the Larynx pptx - د.عبدالله ربيع الخليلي

Anatomy of the Larynx

Dr. Abdullah Alkhalil
FJMC, H.S
MRCS-ENT(UK), DOHNS(LONDON)
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General principles of development

The development of the larynx can be divided into prenatal and postnatal stages.

At birth, the larynx is located high in the neck between the C1 and C4 vertebrae, allowing concurrent breathing or vocalization and deglutition.

By age 2 years, the larynx descends inferiorly; by age 6 years, it reaches the adult position between C4 and C7 vertebrae. This new position provides a greater range of phonation (because of the wider supraglottic pharynx) at the expense of losing this separation of function, i.e., deglutition and breathing.

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General principles of development

The larynx develops from the endodermal lining and the adjacent mesenchyme of the foregut between the fourth and sixth branchial arches.

At 20 days' gestation, the foregut is first identifiable with a ventral laryngotracheal groove. It continues to deepen until its lateral edges fuse.

Trachea becomes separated from the esophagus by the tracheoesophageal septum with a persistent slit like opening into the pharynx

This fusion occurs in the caudal-to-cranial direction, and incomplete fusion results in development of persistent communication between the larynx or trachea and the esophagus

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General principles of development

The larynx grows rapidly during the first 3 years of life, while the arytenoids remain approximately the same size.
Beginning at age 18-24 months, the larynx descends in the neck to achieve its final position at vertebrae C4-C7 by age 6 years.
The larynx elongates as the hyoid, thyroid, and cricoid cartilages separate from each other.
The cricoid cartilage continues to develop during the first decade of life, gradually changing from a funnel shape to a wider adult lumen; therefore, it is no longer the narrowest portion of the upper airway.

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Functions of the larynx

Sound production (phonation). NOTE: phonation = speech.

Regulates amount of air entering the lungs.

Acts as a valve to prevent food in the pharynx from entering the trachea.

Provides a sphincter as part of the Valsalva maneuver (“bearing down”, lifting heavy objects).

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Functions of the larynx

Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness.
Fine manipulation of the larynx is used to generate a source sound with a particular fundamental frequency, or pitch. This source sound is altered as it travels through the vocal tract, configured differently based on the position of the tongue, lips, mouth, and pharynx.
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Functions of the larynx

The vocal folds can be held close together (by adducting the arytenoid cartilages) so that they vibrate. The muscles attached to the arytenoid cartilages control the degree of opening. Vocal fold length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage (either directly by contracting the cricothyroids or indirectly by changing the vertical position of the larynx), by manipulating the tension of the muscles within the vocal folds, and by moving the arytenoids forward or backward. This causes the pitch produced during phonation to rise or fall. In most males the vocal folds are longer and with a greater mass, producing a deeper pitch.

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Functions of the larynx

During swallowing, the backward motion of the tongue forces the epiglottis over the glottis' opening to prevent swallowed material from entering the larynx which leads to the lungs; the larynx is also pulled upwards to assist this process. Stimulation of the larynx by ingested matter produces a strong cough reflex to protect the lungs.

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Laryngeal components

Cartilages.
Extrinsic ligaments.
A cavity (airway) lined by a mucosa.
Fibro-elastic membranes.
Intrinsic skeletal muscles.
Nerves, arteries, veins, and lymphatics.

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The “skeleton” of the larynx

5 Major cartilages:

Thyroid (1)
Cricoid (1)
Epiglottis (1)
Arytenoid (2)
Covered with mucous membranes and skeletal muscles.

Cricothyroid joint (synovial)

The “skeleton” of the larynx

All major cartilages are composed of hyaline cartilage EXCEPT the epiglottis = Elastic cartilage
 Arytenoid cartilages are paired
 They are shaped like pyramids perched atop the cricoid cartilage

Crico-arytenoid joints (synovial)

Thyroid Cartilage

Shield shaped, open posteriorly, angulated anteriorly
Angulation more acute in males
Its function is to shield larynx from injury and provide an attachment to vocal cords
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Adam’s Apple

Cricoid Cartilage

Signet ring shaped
Stronger than thyroid cartilage.
Lamina – 2 to 3 cm from above downwards, considerably broader than anterior arch.

Important from structural & functional point of view

Base for entire larynx
Support to arytenoid
Attachment to intrinsic muscles
Only part of cartilagenous framework that forms continuous 360 degree ring
Once injured or strictured , difficult to resect while preserving laryngeal function

Epiglottis

Thin leaf shaped fibro-cartilage, situated in midline
Upper free end broad & rounded, projects up behind base of tongue
Narrow base called pitiole
This attachment forms lower limit of pre-epiglottis space
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Half of epiglottis projects above hyoid

This part has a laryngeal and lingual surfaces

Infrahyoid portion has no free anterior surface

Forms posterior wall of PES
Epiglottic cartilage contains many pits filled with mucous glands
Little barrier between infrahyoid portion and PES

Arytenoids

Paired cartilages, pyramidal in shape
Base articulated with cricoid
PCA & LCA muscles attach on muscular process
Anterior angle elongated into vocal process which receives insertion of vocal ligament

The arytenoid cartilages have vocal and muscular processes

Anterior Posterior

Minor laryngeal cartilages

Cuneiform cartilages

Corniculate cartilages

Probably support the ary-epiglottic folds – they produce swellings called cuneiform and corniculate tubercles.

Laryngeal Subsites

Supraglottis

Consists of ventricles, false cords, laryngeal surface of epiglottis, aryepiglottic folds and the mucosal expanse.
Posterior tapering shape reduces area of mucosa in posterior region
So majority of SG tumors are epiglottic

Glottis

Consists of true cords, anterior commissure and posterior commissure
Narrow triangular space between the true cords is called rima glottis
Anterior 2/3 is membranous
Posterior third consists of vocal processes of arytenoids
Posterior 1/3 of cords and covering mucosa are called posterior commissure

Sub-glottis

Begins about 5mm below free margins of VC
Consists of a mobile upper and fixed lower part

Extrinsic ligaments

Thyrohyoid ligament
Attaches the larynx to the hyoid – this explains why the larynx is elevated during swallowing.

The thyrohyoid ligaments has apertures for the internal branch of the superior laryngeal nerve and superior laryngeal vessels.

Median cricothyroid ligament (a.k.a. – cricothyroid ligament.

Extrinsic ligaments

Hyo-epiglottic ligament

Cricotracheal ligament
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Laryngeal inlet (Aditus)

The inlet is surrounded by the:

Ary-epiglottic folds.
Epiglottis.
Note the cuneiform and corniculate tubercles – features of the ary-epiglottic folds.

Cavity of the larynx

Coronal section

Sagittal section

Vestibule

Saccule

Ventricle
Infraglottic cavity

Trachea

The walls of the laryngeal cavity contains two vocal folds

Vestibular folds ( false vocal folds).

Vocal folds ( true vocal folds, vocal cords).

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The circumscribed region of the laryngeal cavity that contains the (true) vocal folds is called the glottis.
The spaces between the left and right vestibular and vocal folds are called the rima vestibuli and rima glottidis, respectively.

Rima vestibuli

Rima glottidis

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Intrinsic muscles of the larynx

Perform 4 basic actions:
 Abduct the vocal cords.
 Adduct the vocal cords.
Tense/relax the vocal cords.
Close the laryngeal inlet.
Skeletal muscles innervated by the vagi

Recurrent laryngeal nerve

Superior laryngeal nerve

“Muscles of phonation” do these tasks

Muscles that abduct the vocal cords

Posterior crico-arytenoid muscles
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Abductor of Larynx

Muscles that adduct the vocal cords

Lateral crico-arytenoid muscles & transverse arytenoid muscles.

Adductors of the Vocal Folds

Muscles that tense the vocal cords

Cricothyroid muscles

Thyroid cartilage tilts forward on cricoid cartilage – vocal cords are stretched and become taut.

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Cricothyroid Muscle

Muscles that relax the vocal cords

Thyro-arytenoid muscles

These muscles draw the thyroid cartilage closer to the arytenoid cartilages – thus the vocal cords are no longer taut and relax.

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The vocalis muscles perform fine, regional adjustments of tension

These muscle fibers attach to the vocal processes of the arytenoid cartilage and thyroid angle  They insert at various places along the vocal ligaments.

Subparts of the vocal ligaments can be tensed and relaxed.

Muscles that close the laryngeal inlet

Transverse arytenoid & ary-epiglottic muscles
These muscles draw the ary-epiglottic folds, the epiglottis, and arytenoid cartilages together – narrowing the inlet

Nerve Supply: Derived from the Vagus

Superior Laryngeal Nerve -It leaves the vagus nerve high in the neck
Internal -It provides sensation of the glottis and supraglottis, which includes the pharynx, underside of the epiglottis and the larynx above the cords. Remember: SIS-superior internal sensory.
External -It supplies motor function to the cricothyroid muscle which tenses the vocal cords and could cause laryngopasm.
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Recurrent Laryngeal Nerve -It provides sensation to the subglottic area which includes the larynx below the vocal cords and upper esophagus. It provides motor function to the intrinsic muscles of the larynx.
It branches from the vagus in the mediastinum and turns back up into the neck. On the right, it travels inferior to the subclavian and loops up, and on the left it travel inferior to the aorta and loops up.

Motor supply to intrinsic muscles of larynx

Recurrent laryngeal nerve supplies all laryngeal muscles EXCEPT the cricothyroid  Supplied by external branch of superior laryngeal nerve.

ARTERIAL SUPPLY

Sup. Laryngeal A. from Sup. Thyroid artery
Inf. Laryngeal A. from Inf. Thyroid artery

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Lymphatic drainage of larynx

Lymph vessels follow blood vessels – ultimately draining to deep cervical nodes.
Above the vocal folds  To superior group of deep cervical nodes.
Below the vocal folds  To paratracheal and inferior group of deep cervical nodes.

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END
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