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LARYNX Larynx • Larynx is an air passage, a sphincter and an organ of phonation • Situated in the anterior midline of neck • Extends from upper border of epiglottis to lower border of cricoid cartilage • Lies opposite vertebral level C3 - C6 ( C1-C4 in children) • Communicates with laryngopharynx, Below continuous with the trachea. Skeleton of the larynx • Made up of cartilages • Connected by membranes and ligaments and moved by muscles • Lined by mucous membrane Cartilages • Unpaired cartilages – Epiglottis – Thyroid – Cricoid • Paired cartilages – Arytenoid – Corniculate – Cuneiform Thyroid cartilage • Largest laryngeal cartilage • Made up of hyaline cartilage • Consist of two laminae meeting in the midline at the thyroid angle or Adam's apple. • Posterior borders of each lamina is drawn upward into a superior cornu and downward into inferior cornu. Cricoid cartilage • Shaped like a signet ring and lies below the thyroid cartilage • It has narrow anterior arch and a broad posterior lamina • On each side of the lateral surface is a circular facet for articulation with the inferior cornu of the thyroid cartilage • Upper border of posterior lamina articulate with base of the arytenoid cartilage Arytenoid cartilages • Two in number, pyramidal shaped • Situated at the back of the larynx, • It has an apex above which supports the corniculate and cuneiform cartilages • Base articulates with lamina of cricoid cartilage • It two processes project from the base Corniculate and cuneiform cartilages • Corniculate cartilage: two small nodules that articulate with the apex of the arytenoid cartilage • Cuneiform cartilages: two rod like pieces of cartilages that articulate with the corniculate cartilage Epiglottis • Leaf shaped elastic cartilage • Situated behind the root of the tongue • Its lower end connected with the back of the thyroid cartilage • It is connected in front with the body of the hyoid bone • Sides of the epiglottis connected to the arytenoid cartilages by aryepiglottic folds. Membranes and ligaments of the larynx Thyrohyoid membrane: It connects upper border of thyroid cartilage below and posterior surface of the hyoid bone above - It is thickened in the midline to form the median thyrohyoid ligament -Posterior borders of the membrane also thickened to form the lateral thyrohyoid ligaments -pierced by internal laryngeal nerve and superior laryngeal vessels • - Fibroelastic membrane of the larynx • • • Lies beneath the mucous membrane of the larynx Upper portion is called quadrangular membrane Lower portion is called cricovocal membrane Quadrangular membrane: - extends between the epiglottis and arytenoid cartilages - Its thickened lower margin forms the vestibular ligament • Cricovocal membrane: - connects the cricoid cartilage to arytenoid and thyroid cartilage - Upper thickened border is called vocal ligament - Anterior of each vocal ligament is attached to the deep surface of the thyroid angle, posterior end to the vocal process of the arytenoid cartilage. Ligaments of larynx Hyoepiglottic ligament: attaches the epiglottis to the hyoid bone Thyroepiglottic ligament: attaches the epiglottis to the thyroid cartilage Cricotracheal ligament: connects lower margin of the cricoid cartilage to the first ring of the trachea Inlet of the larynx • Communication between larynx and laryngeal part of the larynx • Boundaries: - In front: upper margin of the epiglottis - Laterally: aryepiglottic fold - Behind: inter arytenoid fold Cavity of the larynx • • 1. • • • Extends from inlet to the lower margin of the cricoid cartilage Divided into 3 parts: Vestibule or upper part: Extends from the upper border of the epiglottis to the vestibular folds Vestibular folds projects medially which is a thickened lower portion of the quadrangular membrane Rima vestibuli: gap between the vestibular folds Cavity of larynx Cavity of the larynx 2. • • • Middle part: Extends from the level of vestibular fold to the vocal fold The vocal folds are white and contain vocal ligament Vocal ligaments extend from the deep surface of the thyroid angle to the vocal process of the arytenoid cartilage Cavity of the larynx • Rima glottidis: - Gap between the vocal folds in front and the vocal process of arytenoid cartilage behind - Lined by stratified squamous epithelium - Devoid of sub mucosa Rima glottidis Cavity of the larynx • Sinus of the larynx: recess between the vestibular and vocal folds • Saccule of the larynx: diverticulum extends upwards from sinus of the larynx between the thyroid cartilage and vestibular fold. 3. Lower part: • Extends from the vocal fold to the lower border of cricoid cartilage • Its walls are formed by cricothyroid ligament and cricoid cartilage Muscles of the larynx • Divided in to two groups (1) extrinsic (2) intrinsic Extrinsic muscles: • Includes elevators and depressors of larynx • Elevators: digastric, thyrohyoid, stylohyoid, mylohyoid and geniohyoid • Depressors: sternothyroid, sternohyoid and omohyoid Intrinsic muscles 1. Cricothyroid: Origin: side of the cricoid cartilage Insertion: lower border and inferior cornu of the thyroid cartilage Action: tenses vocal cords 2. Posterior cricoarytenoid: Origin: back of cricoid lamina Insertion: muscular process of arytenoid cartilage Action: abducts the vocal cords Intrinsic muscles 3. Lateral cricoarytenoid: Origin: upper border of cricoid cartilage Insertion: muscular process of arytenoid cartilage Action: adducts the vocal cords 4. Transverse arytenoid: Origin: back of arytenoid cartilage Insertion: back of the opposite arytenoid cartilage Action: closes the posterior part of the rima glottidis by approximating arytenoid cartilages 5. Oblique arytenoid: extends from the muscular process of arytenoid artilage to the vocal process of opposite arytenoid cartilage Intrinsic muscles 6. Thyroarytenoid Origin: inner surface of thyroid cartilage Insertion: arytenoid cartilage 7. vocalis: It extends from the vocal process of arytenoid cartilage to the deep surface of thyroid angle Action: ralaxes the vocal cords 8. Aryepiglotticus: extends from the arytenoid cartilage to the side of epiglottis Action: close the laryngeal inlet 9. Thyroepiglottis: Origin: medial surface of thyroid cartilage Insertion: lateral margin of the epiglottis Action: widens the inlet Adductors of the Vocal Folds Abductor of Larynx Movements of the vocal cords Nerve supply • Sensory supply - Above the vocal folds: internal laryngeal nerve - Below the vocal cords: recurrent laryngeal nerve • Motor supply: - All intrinsic muscles supplied by recurrent laryngeal nerve - Exception: cricothyroid – external laryngeal nerve Blood supply and lymph drainage • Above the vocal folds: superior laryngeal artery • Below the vocal folds: inferior laryngeal artery • Lymph vessels drain into deep cervical lymph nodes Damage to laryngeal nerves • Recurrent laryngeal nerve: • Unilateral – Paralysis of vocal folds (midway between abduction and adduction) – Hoarseness of voice initially – Compenates by other fold within weeks – Normal respiration • Bilateral: – Loss of voice – Stridor ( noisy respiration) – Neutral position ( cadaveric position) • Partial damage: – Paralysis of abductors than adductors – When bilateral acute breathlessness (dyspnea) • External laryngeal nerve: – Weakness of voice due to loss of vocal cord tension