ANATOMY AND PHYSIOLOGY OF THE LARYNX

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ANATOMY AND PHYSIOLOGY OF THE LARYNX : 

ANATOMY AND PHYSIOLOGY OF THE LARYNX

Slide 2: 

Situated at the upper end of trachea Opposite 3rd – 6th cervical vertebrae (men) Higher in women and children 44 x 43 x 36 mm / 36 x 41 x 26 mm Infants – smaller, narrow lumen, funnel-shaped, higher, cartilages softer & collapse easily At puberty AP diameter in males doubles

Laryngeal cartilages : 

Laryngeal cartilages THYROID CARTILAGE Shield like , longest Meet at midline – Thyroid notch ( angle 90 /120 degrees) Fused anterior border – laryngeal prominence Intrathyroid cartilage separates the 2 laminae in childhood Posteriorly the laminae diverge Superior and inferior cornua

Slide 4: 

Superior cornu – long, narrow, curves upwards, backwards and medially, lateral thyroid ligament attached to tip Inferior cornu – shorter, thicker, curves downwards & medially, oval articular facet Oblique line – from superior thyroid tubercle (anterior to root of superior horn ) to inferior thyroid tubercle (on lower border of lamina) > site of attachment of muscles

Slide 5: 

Inner aspect smooth, mucosa covered Thyroepiglottic ligament, vestibular and vocal ligaments, thyroarytenoid, thyroepiglottic & vocalis muscles Superior border – thyrohyoid ligament Inferior border – cricothyroid ligament

Slide 7: 

CRICOID CARTILAGE :- Only complete cartilaginous ring (signet) Forms most of the posterior wall of larynx Broad quadrilateral lamina posteriorly and narrow arch anteriorly Articular facet for inferior cornu at junction of arch and lamina Articular facets for arytenoids on lamina Vertical ridge on midline for attachment of longitudinal muscles of the oesophagus

Slide 9: 

ARYTENOID CARTILAGES :- Placed on upper & lateral border of lamina Three sided pyramid Vocal process – vocal fold Muscular process – posterior & lateral cricoarytenoid Anterolateral surface – vestibular ligament, vocalis & lateral cricoarytenoid muscles Medial surface – mucosa covered

Slide 10: 

Apex – articulates with corniculate cartilage Posterior surface – covered by transverse arytenoid Base – concave, articular facet Synovial joint with lax capsular ligament Rotatory and medial & lateral gliding movement.

Slide 12: 

CORNICULATE (Wrisberg) – Small, conical Elastic fibrocartilage Synovial joint or fused with apices of arytenoid Situated in the aryepiglottic fold CUNEIFORM (Santorini) – Small, elongated Elastic fibrocartilage Lateral to corniculate

Slide 13: 

EPIGLOTTIS :- Thin, leaf-like, elastic fibrocartilage Projects upward behind tongue & hyoid Narrow stalk attached below thyroid notch by thyroepiglottic ligament Upper part directed upwards & medially Superior margin free Sides attached to arytenoid catilage by aryepiglottic fold. tubercle in the lower part of posterior surface

Slide 14: 

Pits on cartilage – mucous glands Anterior surface – mucosa covered Median and lateral glossoepiglottic fold Hyoepiglottic ligament Pre-epiglottic space – between epiglottis & thyrohyoid membrane, fat filled space Neonates & infants – omega shaped, long, floppy

Slide 16: 

Calcification – Elastic fibrocartilage – epiglottis, corniculate, cuneiform & apices of arytenoid – not calcified Hyaline cartilage – calcification by late teens / early twenties Thyroid – starts at inferior cornu, rim is calcified leaving a translucent window till old age Calcification of posterior part of lamina & arytenoid – FB Arytenoid – body & muscular process – 4th decade, vocal process not calcified

Ligaments of the larynx : 

Ligaments of the larynx Extrinsic ligaments – Connect cartilages to hyoid and trachea Thyrohyoid Membrane :- Between upper border of thyroid & upper border of posterior surface of body and greater cornu of hyoid Fibroelastic tissue – condensed anteriorly to form median thyrohyoid ligament & posteriorly lateral thyrohyoid ligaments Cartilago triticea – small nodule Pierced by internal branch of superior laryngeal nerve & superior laryngeal vessels

Slide 18: 

Cricotracheal ligament – lower border of cricoid to 1st tracheal ring Hyoepiglottic ligament – epiglottis to back of body of hyoid

Intrinsic ligaments : 

Intrinsic ligaments Connect the cartilages to each other. Internal framework Quadrilateral Membrane :- Border of epiglottis and arytenoid cartilage Upper margin forms framework of aryepiglottic fold Lower margin – vestibular ligament which underlies the vestibular fold or false cords

Slide 20: 

Conus Elasticus:- Cricovocal ligament Attached below to the upper border of cricoid cartilage Above between midpoint of laryngeal prominence to vocal process of arytenoid Free upper border forms vocal ligament , framework of vocal fold / true cord Anteriorly thickened to form cricothyroid ligament

Cavity of the larynx : 

Cavity of the larynx Divided by vestibular & vocal folds into 3 compartments Superior vestibule Ventricle / sinus of the larynx Subglottic space Rima glottidis / glottis Rima vestibuli

Slide 22: 

Pre-epiglottic space (Space of Boyer) :- Anterior – thyrohyoid ligament & hyoid Posterior – epiglottis Superior – hyoepiglottic ligament Lateral – continuous with paraglottic space Para-glottic space:- Lateral – thyroid cartilage Medial – conus elasticus & quadrangular membrane Posterior – anterior reflection of PFS mucosa

LARYNGEAL VENTRICLE : 

LARYNGEAL VENTRICLE Laryngeal sinus Elongated recess between vestibular & vocal folds Opens through a narrow slit into middle segment of larynx From anterior part a pouch extends between vestibular folds & inner surface of thyroid cartilage - saccule Mucous membrane lining the saccule contains numerous mucous glands

Vestibular folds : 

Vestibular folds Thick, pink folds of mucous membrane Encloses the vestibular ligament Anterior attachment is to angle of thyroid cartilage, inferior to epiglottis Posterior attachment to anterolateral surface of arytenoid cartilage superior to vocal process

Vocal fold : 

Vocal fold Extends from the middle of angle of the thyroid cartilage to vocal process of arytenoid cartilage Layered structure – mucosa & muscle Mucosa – epithelium : stratified squamous Lamina propria – superficial, intermediate and deep layers Superficial – loose fibrous substance : Reinke’s space – vibrates maximum during phonation

Slide 26: 

Intermediate layer – elastic fibres Deep layer – collagenous fibres Intermediate & deep layers form vocal ligament Deep to vocal ligament – vocalis muscle Anterior and posterior macula flava protect vocal fold from damage due to vibration

Slide 27: 

Multilayered vibrator Cover – epithelium and superficial layer of lamina propria Transition – intermediate & deep layer Body – vocalis muscle Blood vessels run parallel to the edge

Slide 29: 

GLOTTIS :- Elongate fissure between the vocal folds anteriorly and the vocal process & bases of the arytenoid posteriorly. Region between vocal cords – 3/5th of length – intermembranous part Remainder – intercartilaginous part

Mucous membranes of the larynx : 

Mucous membranes of the larynx Closely attached over the posterior surface of the epiglottis, corniculate, cuneiform & vocal ligament Loosely attached elsewhere – swollen Epithelium – squamous / ciliated columnar or transitional Numerous mucous glands except at the vocal folds ( mucous from saccule ) Few taste buds on posterior surface of epiglottis and AEF

Blood supply : 

Laryngeal branch of superior thyroid (br. of external carotid) Laryngeal branch of inferior thyroid (br. of thyrocervical trunk of 1st part of subclavian) Cricothyroid branch of superior thyroid Superior & middle thyroid vein, facial vein > internal jugular Inferior thyroid vein > brachiocephalic veins Blood supply

Lymphatic drainage : 

Lymphatic drainage Separated by vocal fold into upper and lower group Above vocal fold -> upper deep cervical nodes Below vocal fold -> prelaryngeal, pretracheal & lower deep cervical Vocal folds firmly bound down to vocal ligament -> relative absence of lymphatics

Nerve supply : 

Nerve supply Vagus – superior laryngeal nerve - Recurrent laryngeal nerve Superior laryngeal arises from the inferior ganglion of the vagus + br. from superior cervical sympathetic ganglion At level of greater horn of the hyoid divides into external & internal branches External > cricothyroid Internal > pierces thyrohyoid membrane >

Slide 34: 

Divides into upper & lower branches > pierces inferior constrictor > unites with ascending branch of recurrent laryngeal nerve ( Galen’s anastomosis ) Recurrent laryngeal nerve – Right – loops around right subclavian artery Left – Loops around the aortic arch & ligamentum arteriosum Ascends in the tracheo-esophageal groove

Slide 35: 

Enters the larynx behind cricotracheal joint Divides into motor & sensory branch Motor – all intrinsic muscles of larynx except cricothyroid Sensory – below the level of vocal folds

PHYSIOLOGY : 

PHYSIOLOGY Three main functions of the larynx Protective Respiratory Phonatory

PROTECTIVE FUNCTION : 

PROTECTIVE FUNCTION Stimulation of superior laryngeal nerve by touch chemical & thermal stimulation > evoked action potential in adductor branches of recurrent laryngeal nerve Polysynaptic brainstem reflex Adduction occurs at three muscular tiers 1st – AEF 2nd – false cords 3rd – true cords Physiologic exaggeration of glottic closure reflex - laryngospasm

RESPIRATORY FUNCTION : 

RESPIRATORY FUNCTION Posterior cricoarytenoids & cricothyroid Driven by medullary respiratory center Regulated by afferent impulses originating in the chest Posterior cricoarytenoid increases horizontal diameter of glottis Cricothyroid increases AP diameter Cricothyroid also plays a role in control of expiratory resistance and respiratory rate

PHONATORY FUNCTION : 

PHONATORY FUNCTION Vocal folds vibrate at 100-300 Hz (normal conversation to >1000 Hz (singing) Neurochronaxic theory Aerodynamic theory

Phonation : 

Phonation Adduction of vocal folds & adduction and medial rotation of arytenoids Vocal folds are lengthened Changes in length & tension control pitch Tension in the vocal fold, decrease in subglottic air pressure & sucking-in-effect of escaping air bring the vocal folds together

Slide 42: 

Air from subglottis released in small puffs Vocal folds thinner at high pitch Mucosal wave travels from inferior to superior surface Sound produced is modified by resonating chambers above & below the larynx Converted to phonemes by articulation of pharynx, tongue, palate, teeth & lips

QUESTIONS : 

QUESTIONS

Slide 44: 

Pre-epiglottic space is also known as ____ What fraction of the glottis is intercartilaginous ? The apex and vocal process of the arytenoid calcifies by the fourth decade – True / False ? Anastomosis of Galen is formed by _____ & _______ Movements possible at the cricoarytenoid joint are _______ & _______