Anatomy and Physiology of the Larynx 7/15/2012 www.nayyarENT.com Dr. Supreet Singh Nayyar, AFMC For more presentations, please visit www.nayyarENT.com

Objectives To discuss the basic anatomy of the larynx To enumerate the main functions of the larynx 7/15/2012 www.nayyarENT.com

Embryology Respiratory system – outgrowth of primitive pharynx 3.5 weeks – laryngotracheal groove, ventral aspect of foregut 3 weeks - Hypobrancial eminence – gives rise to furcula -> epiglottis 5th week – Arytenoid masses 5-7 weeks – laryngeal lumen is obliterated 9 weeks – oval shape lumen reestablished 8-10 weeks – Formation of true and false vocal cords 12th week – ventricles Laryngeal muscles – derivatives of mesoderm of 4th and 5th arches (CN X) 7/15/2012 www.nayyarENT.com

Laryngeal Cartilages Paired Unpaired: Arytenoid cartilage Corniculate cartilage Cuneiform cartilage Unpaired: Thyroid cartilage Cricoid cartilage Epiglottis 7/15/2012 www.nayyarENT.com

Thyroid Cartilage Hyaline cartilage Largest 7/15/2012 Hyaline cartilage Largest Encloses the larynx anteriorly and laterally Two alae Ossification www.nayyarENT.com This cartilage has two alae/wing which meet anteriorly, they form a depression called the THYROID NOTCH before meeting at the protruberance of the Adam’s apple or laryngeal prominence. Posteriorly, each wing has a superior cornu (extending upward about 2 cm) and inferior cornu (articulates w/cricoid cartilage below; ONLY DIRECT ARTICULATION, all others being maintained by muscles or ligaments) Ossifies at 20-30 years of age, begins in the inferior margin and progress cranially

Cricoid Cartilage Hyaline cartilage 7/15/2012 Hyaline cartilage Directly below the thyroid cartilage Strongest Shape: Signet ring Lamina – flat portion Only complete annular support of the larynx Articulates w/ Inferior cornu of the thyroid cartilage www.nayyarENT.com Ossifies after the thyroid cartilage, first part to be calcified being the superior portion (w/c can be mistaken for a foreign body) Calcification progresses caudally. Lamina – flat portion of the ring llocated posteriorly and extends upward to form the POSTERIOR border of the larynx Only complete annular support of the laryngeal skeleton; preservation essential to maintain the enclosed airways. Level: Adult: C6-C7 Children: C3-C4 Posterolaterally, cricoid articulates w/ Inferior cornu of the thyroid cartilage, which forms true synovial joints (permit a ROCKING action of the cricoid cartilage on the thyroid cartilage and a slight anteroposterior SLIDING motion (cricoid cart. Supports the 2 arytenoid cartilages on posterosuperior aspect)

Epiglottis Fibroelastic cartilage Leaf-shaped structure 7/15/2012 Fibroelastic cartilage Leaf-shaped structure Petiole – small narrow portion of the glottis www.nayyarENT.com Attached to the INSIDE of the thyroid cart. Anteriorly and projects upward and backward above the laryngeal opening. Petiole – small narrow portion of the glottis that is attached to the thyroid cart. The epiglottis is attached to the hyoid bone by the hyoepiglottic ligament. To the posterior part of the tongue by the median glossoepiglottic fold. To the sides of the pharynx by the lateral glossoepiglottic folds. To the thyroid cartilage by the thyroepiglottic ligament. The mucous membrane covering the epiglottis is reflected to the posterior part of the tongue as one medial and two lateral glossoepiglottic folds. Between these folds are depressions called epiglottic valleculae.

Arytenoid Cartilage Mostly hyaline cartilage Smaller in size 7/15/2012 Mostly hyaline cartilage Smaller in size Responsible for opening and closing of the larynx Shape: pyramidal www.nayyarENT.com Calcify at the 3rd decade (Hyoid – ossifies fr. 6 centers shortly after brith, complete by 2 years of age) Arytenoids rest on the upper edge of the cricoid lamina at the posterior border of the larynx

Arytenoid Cartilage Anterior Lateral Articulation 7/15/2012 Anterior Vocal process - receives the attachement of the mobile end of each VC Lateral Muscular process Articulation Cricoarytenoid joint www.nayyarENT.com Mobile end of VC – posterior Lateral promincence of each arytenoid cart. Is known as Muscular process, becoz of insertion site of numerous muscles Articulation of arytenoids with cricoid cart. Is at the CRICOARYTENOID JOINT, w/c permits a WIDE range of motion in 3 directions

Corniculate Cartilages Fibroelastic Cartilages of Santorini Small cartilages above the arytenoid and in the aryepiglottic folds 7/15/2012 www.nayyarENT.com

Cuneiform Cartilages Firboelastic cartilages Cartilages of Wrisberg Elongated pieces of small yellow elastic cartilage in the aryepiglottic folds 7/15/2012 www.nayyarENT.com

Triticeous Cartilage Cartilago triticea 7/15/2012 Cartilago triticea Small elastic cartilage in the lateral thyrohyoid ligament www.nayyarENT.com When calcified, it can be mistaken as a foreign bidy in soft tissue Xray films

Laryngeal Ligaments Intrinsic Extrinsic Elastic membrane 7/15/2012 Intrinsic Elastic membrane Quadrangular membrane Conus elasticus (cricovocal membrane) Median cricothyroid ligament Vocal Ligament Thyroepiglottic ligament Extrinsic Thyrohyoid membrane and ligaments Cricothyroid membrane and ligaments Cricotracheal ligament Epiglottis www.nayyarENT.com

Extrinsic Ligaments Thyrohyoid membrane pierced on each side by: 1. Superior laryngeal vessels 2. Internal branch of superior laryngeal nerve Median thyrohyoid ligament – thickened median portion Lateral thyrohyoid ligament – thickened posterior border - where cartilago triticea is often found 7/15/2012 www.nayyarENT.com Thyrohyoid m&L –attach thyroid cart. To hyoid bone

Extrinsic Ligaments Cricothyroid membrane and ligaments May be pierced for emergency tracheotomy (cricothyrotomy) 7/15/2012 www.nayyarENT.com Obvious from its name, the CT m&L connect the thyroid and cricoid cart. Cricothyrotomy – little fear of bleeding; however becoz of proximity to the vocal cords, this space shld not be used for prolonged intubation, as scar tissue may be produced.

Extrinsic Ligaments Cricotracheal Ligament Epiglottis Attaches the cricoid cartilage to the first attached ring Epiglottis suspended in position by membranous connections to the hyoid bone, thyroid cartilage and base of the tongue 7/15/2012 www.nayyarENT.com

Intrinsic Ligaments Elastic membrane Quadrangular membrane 7/15/2012 Elastic membrane Divided into upper and lower parts by the ventricle of the larynx Quadrangular membrane Upper part of the elastic membrane Boundaries Epiglottis , arytenoid, corniculate cartilage, false cord Forms part of wall between upper pyriform sinus and laryngeal vestibule www.nayyarENT.com Elastic m.-lies beneath the laryngeal mucosa, Fibrous framework of the larynx Ventricle of the larynx (ventricle of Morgagni) Quad membrane - Boundaries: extending from LATERAL margin of epiglottis to arytenoid and corniculate cart., and INFERIORLY to the false cord.

Intrinsic Ligaments Conus elasticus (cricovocal membrane) 7/15/2012 Conus elasticus (cricovocal membrane) Lower part of elastic membrane Composed mainly of yellow elastic tissue Boundaries Inferior: superior border of cricoid cartilage Superoanterior: deep surface of angle thyroid cartilage Superoposterior: vocal process of arytenoid cartilage Median cricothyroid ligament – thickened anteior part Vocal Ligament – free upper edge Thyroepiglottic ligament www.nayyarENT.com Median cricothyroid ligament – thickened anteior part of conus elasticus Vocal Ligament – is d free upper edge of the conus elasticus (strongest part), forms the framework of the vocal cord Thyroepiglottic ligament – ataches epiglottis to the thyroid cartilage

Cavity of the Larynx Divided into 3 parts: Vestibule Ventricle 7/15/2012 Divided into 3 parts: Vestibule Ventricle Subglottic space www.nayyarENT.com Divided into 3 parts by 2 folds of mucous membrane, namely the true and false cords. Vestibule – lies bet. Inlet and edges of false cords Ventricle (Morgagni) - Deep, spindle-shaped recess bet. True and false cords, lined by a mucous membrane that is covered externally by thyroarytenoid muscle Subglottic space – lies bet. True VC and lower border of cricoid cartilage

Cavity of the Larynx Vestibule – boundaries: 7/15/2012 Vestibule – boundaries: Anterior: posterior surface of epiglottis Posterior: interval between arytenoid cartilages Lateral: inner surface of aryepiglottic folds and upper surfaces of the false cord www.nayyarENT.com

Cavity of the Larynx Ventricle 7/15/2012 Adduction: Phonation, slit-like appearance Glottis (rima glottidis) Abduction: Respiration, wide and triangular Ventricle Saccule – conical pouch at anterior part www.nayyarENT.com Saccule – conical pouch that ascends fr anterior part of the ventricle, lies bet. Inner surface of thyroid cartilage and false cord; has numerous mucous glands open into the surface of its lining mucosa for lubricating the vocal cords. Glottis – space bet. Free margin of the true VC, opening/aperture Posterior glottic chink in adult: 18-19mm; New born: 4mm; total glottic chink in a newborn: 14mm2

Cavity of the Larynx Subglottic space Preepiglottic space Boundaries: 7/15/2012 Subglottic space Preepiglottic space Boundaries: Anterior: thyrohyoid membrane Anteroasuperior: hyoid Superior: vallecula Posterior: part of the epiglottis Lateral: hyoepiglottic ligament www.nayyarENT.com Subglottic space – lies bet. True VC and lower border of cricoid cartilage Preepiglottic space – a wedge-shaped space lying in front of the epiglottis

Cavity of the Larynx False Cords (ventricular bands) True cords 7/15/2012 False Cords (ventricular bands) Anteriorly: angle of the thyroid cartilage Posteriorly: bodies of the arytenoid cartilage True cords Voice production Protection of lower respiratory tract Anteriorly,: angle of thyroid cartilage Posteriorly: vocal processes of the arytenoid cartilages Enclose vocal ligament and a major part of the vocalis muscle www.nayyarENT.com False cords – upper set of two horizontal folds on each side of the laryngeal cavity. TVC – covering epith. Is closely bound down to underlying vocal ligament, blood supplu here is poor hence the pearly white appearance of the vocal cords in life.

Laryngeal Joints Cricothyroid Joint Cricoarytenoid Joint Between inferior cornu of the thyroid cartilage and facet on the cricoid cartilage at the junction of the arch and lamina Two movements: Rotation Gliding Cricoarytenoid Joint bet. base of the arytenoid cartilage and the facet on the upper border of the lamina of the cricoid cartilage Two movements: Rotation Gliding 7/15/2012 www.nayyarENT.com Cricothyroid Joint - Synovial joint with a capsular ligament bet. Inferior cornu of the thyroid cartilage and the facet on the cricoid cartilage at the junction of the arch and lamina. Rotation – thru a transverse axis Gliding – slightly Cricoarytenoid Joint - Synovial joint with a capsular ligament bet. Base of the arytenoid cartilage and the facet on d upper border of the lamina of the cricoid cartilage Rotation – arytenoid rotates on a vertical axis, vocal process moves medially or laterally Gliding – arytenoids move toward or away from each other. (strong posterior cricoarytenoid ligament prevents excessive movements of the arytenoids on the cricoid)

Laryngeal Muscles Intrinsic Muscles Extrinsic Muscles Depressor group 7/15/2012 Extrinsic Muscles Depressor group Elevator group Constrictor muscles Pharyngeal muscles Intrinsic Muscles Interarytenoid muscle Transvers Oblique Post. Cricoarytenoid m. Lateral cricoarytenoid m. Thyroarytenoid m. Cricothyroid m. www.nayyarENT.com Intrinsic muscles, all are paired except Interarytenoid m. Larynx moves up during swallowing, down after. The extrinsic muscles move the larynx as a whole. The infrahyoid muscles or straps (omohyoid, sternohyoid, and sternothyroid) are depressors of the hyoid bone and the larynx, whereas the suprahyoid muscles (stylohyoid, digastric, mylohyoid and geniohyoid) and the stylopharyngeus are elevator of the hyoid bone and larynx.

Depressor muscles Origin Insertion Action Sternohyoid (C2, C3) manubrium of sternum and medial end of clavicle oblique line of the thyroid cartilage depresses/stabilizes the hyoid bone Thyrohyoid (C1) lower border of the hyoid bone elevates the larynx; depresses/stabilizes the hyoid bone Omohyoid (C2, C3) superior border of scapula near the suprascapular notch inferior border of hyoid bone depresses, retracts and steadies the hyoid during swallowing and speaking 7/15/2012 www.nayyarENT.com Sternothyroid Muscle - a thin muscle located deep to the sternohyoid muscle, and is shorter and wider than it. Inferior attachment: posterior surface of manubrium of sternum. Superior attachment: oblique line of thyroid cartilage. Innervation: C2 and C3 by a branch of the ansa cervicalis. It depresses the hyoid bone and larynx after it has been elevated by muscles during swallowing and vocal movements. It also pulls the thyroid cartilage away from the hyoid bone, thereby opening the laryngeal orifice.

Elevator muscles Origin Insertion Action Geniohyoid (C1) inferior mental spine of mandible body of hyoid bone pulls the hyoid bone anterosuperiorly, and shortens the floor of the mouth and widens the pharynx Digastrics (Ant. CN V; Post. N. VII) anterior belly-digastric fossa of mandible, posterior belly-mastoid notch of temporal bone intermediate tendon to body and greater horn of hyoid bone depresses the mandible and raises the hyoid bone. Also, it steadies the hyoid bone during swallowing and speaking Mylohyoid (V) mylohyoid line of mandible raphe and body of hyoid bone elevates the hyoid bone, floor of the mouth and the tongue during swallowing and speaking Stylohyoid (VII) styloid process of the temporal bone elevates and retracts the hyoid bone, thereby elongating the floor of the mouth 7/15/2012 www.nayyarENT.com

Constrictor muscles Origin Insertion Action Middle constrictor m. (CN X) stylohyoid ligament and greater and lesser horns of hyoid bone median raphe of pharynx constricts pharyngeal cavity; influence the position of the larynx during phonation Inferior constrictor m. (CN X) Oblique lines of thyroid cartilage & side of cricoid cartilage 7/15/2012 www.nayyarENT.com

Elevator muscles Origin Insertion Action Stylopharyngeus (CN IX) styloid process of temporal bone posterior and superior borders of thyroid cartilage with palatopharyngeus muscle elevates the pharynx and larynx and expands the sides of the pharynx Salpingopharyngeus (pharyngeal plexus) cartilaginous part of the auditory tube blends with palatopharyngeus muscle elevates the pharynx and larynx and opens the orifice of the auditory tube during swallowing Palatopharyngeus hard palate and palatine aponeurosis lateral wall of pharynx tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing 7/15/2012 www.nayyarENT.com

Muscles Controlling the Laryngeal Inlet 7/15/2012 Intrinsic Muscles Origin Insertion Action Interarytenoid m., oblique (RLN) muscular process of the arytenoid cartilage posterior surface of the contralateral arytenoid cartilage, near its apex draws arytenoid cartilages together, adducting the vocal folds (closure of glottis) Thyroepiglottic (ELN) inner surface of the thyroid cartilage near the laryngeal prominence lateral surface of the epiglottic cartilage draws the epiglottic cartilage downward www.nayyarENT.com Muscles controlling the laryngeal inlet

Muscles Controlling Movements of the Vocal Cords Intrinsic Muscles Origin Insertion Action Cricothyroid (ELN) arch of the cricoid cartilage inferior border of the thyroid cartilage draws the thyroid cartilage forward, lengthening the vocal ligaments, tenses vocal cords Thyroarytenoid (vocalis, ILN) inner surface of the thyroid cartilage lateral border of the arytenoid cartilage relaxes and adducts the vocal folds Lateral cricoarytenoid (ILN) muscular process of the arytenoid cartilage Adducts the vocal cords by rotating the arytenoid cartilage 7/15/2012 www.nayyarENT.com Muscles controlling Movements of the Vocal Cords ELN –ext laryngeal branch from SLN(CN X) ILN –inferior laryngeal nerve from RLN (CN X)

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Muscles Controlling Movements of the Vocal Cords 7/15/2012 Intrinsic Muscles Origin Insertion Action Posterior cricoarytenoid (ILN) posterior surface of the lamina of the cricoid cartilage muscular process of the arytenoid cartilage Abducts the vocal cords by rotating the arytenoid cartilage Interarytenoid m., transverse (ILN) posterior surface of the arytenoid cartilage posterior surface of the contralateral arytenoid cartilage Closes posterior part of rima glottidis by approximating arytenoid cartilages www.nayyarENT.com Muscles controlling Movements of the Vocal Cords ELN –ext laryngeal branch from SLN(CN X) ILN –inferior laryngeal nerve from RLN (CN X)

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Mucous Membrane Stratified squamous epith.: over vocal cords and upper part of vestibule of larynx Ciliated columnar epith.: remainder of the cavity Mucous glands: Ventricles and sacculi Posterior surface of epiglottis Margins of aryepiglottic folds Reinke’s layer of connective tissue: No glands and no lymph vessels 7/15/2012 www.nayyarENT.com Margins of aryepiglottic folds – none on he free edges of the vocal cords Reinke’s layer of connective tissue – lies immediately under the epith. Of larynx and superficial to elastic layer. NO GLANDS BENEATH AND NO LYMPH VESSELS IN IT.

Vocal Folds 7/15/2012 www.nayyarENT.com

Nerve Supply Supplied by Vagus nerve: Superior laryngeal n. Internal branch (sensory) – areas above the glottis External branch (motor and sensory) Motor – Cricothyroid muscle Sensory – Anterior infraglottic larynx at level of cricothyroid membrane Inferior (recurrent) laryngeal n. Motor – all intrinsic laryngeal muscles of SAME side (except cricothyroid) and interarytenoid muscle of BOTH sides Sensory – areas below the glottis 7/15/2012 www.nayyarENT.com RLN – longer course on L than R, L: turns around arch of aorta, R: around subclavian artery Nucleus ambiguus – somatic motor nucleus of CN IX, X, XI - supplied by PICA (fr. Veterbal a.) and AICA (fr. Basilar artery)

Blood Supply Upper Larynx Lower Larynx External carotid artery Superior thyroid artery Superior laryngeal artery Lower Larynx Subclavian artery Thyrocervical artery Inferior thyroid artery Inferior laryngeal artery 7/15/2012 www.nayyarENT.com

Venouos Drainage Upper Larynx Lower Larynx Superior laryngeal vein Superior thyroid vein Internal jugular vein Lower Larynx Inferior laryngeal vein Inferior thyroid vein Innominate vein 7/15/2012 www.nayyarENT.com

Lymphatic Drainage Main: Deep Cervical group L.N. Supraglottic area 98%: Pedicle Ant. End of aryepiglottic fold -> pass laterally and leave the larynx through the thyrohyoid membrane ->Upper deep cervical nodes (bet. Digastric tendon and omohyoid muscle) 2%: Lower cervical chain or spinal accessory chain 7/15/2012 www.nayyarENT.com Generally, Lymg drainage from each half of larynx is SEPARATE, LITTLE CROSSOVER/MIXING, although it does cross the midline in supra- and infra-glottic areas. Contralateral drainage more likely in INFRAGLOTTIC areas; ergo, less consistent patterns of mets. Lymphatics arising from larynx drain mainly into deep cervical LN Vocal cord contain SCARCELY any lymphatic channels

Lymphatic Drainage Infraglottic area – 3 pedicles 1. Anterior pedicle -> cricothyroid membrane -> prelaryngeal (Delphian) nodes ->deep inferior cervical nodes 2. 2 Posterolateral pedicles -> cricotracheal membrane -> paratracheal chain/others to inferior jugular chain 7/15/2012 www.nayyarENT.com

Physiology For more presentations in ENT, visit www.nayyarENT.com 7/15/2012 For more presentations in ENT, visit www.nayyarENT.com www.nayyarENT.com

Basic Functions Protection Respiration Phonation Fixation of chest Closure of glottis 7/15/2012 www.nayyarENT.com Closure of glottis – helps to increase intrathoracic and intraabdominal pressure and aids in lifting, digging, defecation, vomiting, urination or childbirth

Protection Acts as a sphincter Closure of the laryngeal inlet Closure of the glottis Cessation of respiration Cough relfex, expulsion of secretions and foreign bodies 7/15/2012 www.nayyarENT.com Prevents entrance of ANYTHING but AIR into the lung

Protection 3 Sphincteric tiers of airway protection: 7/15/2012 3 Sphincteric tiers of airway protection: Contraction of superior division of the thyroarytenoid muscles Contraction of middle thyroarytenoid fibers Contraction of inferior division of thyroarytenoid www.nayyarENT.com Unilateral SLN paralysis may lead to aspiration (failure of ipsilateral cord closure) despite integrity of both RLNs *(one SLN DOES NOT produce simultaneous activation of the contralateral adductor musculature) 3 Sphincteric tiers of airway protection: 1.Contraction of superior division of the thyroarytenoid muscles contained in the aryepiglottic folds 2.Contraction of middle thyroarytenoid fibers in false cords 3.Contraction of inf. Division of thyroarytenoid at the level of true cord (MOST SIGNIFICANT barrier to aspiration owing to the upturned border of the cord margin) SLN stimulation – produces strong laryngeal ADDUCTOR response and inhibition of laryngeal abductor activity, resulting in various degrees of reflex apnea. Laryngeal spasm – mediated solely by SLN

Respiration Assists in regulation of gaseous exchange with the lung and maintenance in acid-base balance Glottis opens a fraction of a second before air is drawn in by descent of the diaphragm 7/15/2012 Posterior cricoarytenoids Phasic inspiratory abduction Synchronous w/respiration Cricothyroid muscle Phasic inspiratory contraction/adduction Increases AP diameter of glottic chink www.nayyarENT.com By active muscular dilatation of the laryngeal aperture – meaning by opening of the glottis, which occurs with rhythmic bursts of activity of RLN. Phasic inspiratory abduction – posterior cricoarytenoids – synchronous with respiration Phasic inspiratory contraction – cricothyroid m. (vocal cord adductor and isotonic tensor) –increases AP diameter of of glottic chink. *both are driven by medullary respiratory center

Phonation in brief Voice produced by vibration of the vocal cords Fundamental tone produced at the larynx Modified by resonating chambers of the upper aerodigestive tract 7/15/2012 www.nayyarENT.com

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