4. Anatomy of Larynx.pdf

ANATOMY OF LARYNX - Specialized organ that provides protective sphincter at the inlet of the air passage - If the protective function is disturbed, laryngeal incompetence results; and food and fluid may be aspirated into trachea - Responsible for the voice production (voice box or organ of phonat...

ANATOMY OF LARYNX - Specialized organ that provides protective sphincter at the inlet of the air passage - If the protective function is disturbed, laryngeal incompetence results; and food and fluid may be aspirated into trachea - Responsible for the voice production (voice box or organ of phonation) - Upward and downward movements of larynx help in swallowing - Above it communicates with the laryngopharynx - Below it continues as w/the trachea FUNCTIONS - Phonation - Protection - Respiration - Deglutition - Located in the anterior neck at the level of C3 – C6 vertebrae. - NB: In children/ females it lies at a higher level. Until puberty its size in both males and females is more or less the same. - After puberty larynx in the male grows rapidly and becomes larger than the larynx in the female. - In males the characteristic pubertal growth of angle of thyroid cartilage (Adam’s apple) makes the voice louder and low-pitched. - In females the pubertal growth of larynx does not differ much from a child, hence the pitch of the voice is high in both females and children - Length is 44mm in males and 36mm in females. NB: CLINICAL CORRELATIONS - Examination of larynx – laryngoscopy Infection and inflammation of larynx – laryngitis - - Clinically trachea is palpated in the suprasternal notch, normally it is median in position - Trachea may be compressed by pathological enlargements of the thyroid, thymus, lymph nodes and aortic arch. This causes dyspnoea, irritative cough and often husky voice - Tracheostomy – is an reversible emergency operation done in cases of laryngeal obstruction. It is commonly done in retrothyroid region after cutting the isthmus of the thyroid gland. STRUCTURE ASSOCIATED LAB/ LECTURE PHOTOS SKELETON OF THE LARYNX - Made up of three unpaired and three paired cartilages - Cartilages are connected by membranes and ligaments and moved by muscles - Lined by mucous membrane Unpaired Cartilages - Thyroid Cartilages - Cricoid Cartilages - Epiglottis Paired Cartilages - Arytenoid Cartilage - Corniculate Cartilage - Cuneiform Cartilage - The caudal part of hypobranchial eminence forms the epiglottis - The remaining cartilages of larynx are derived from 4th to 6th pharyngeal arches Thyroid Cartilage - Largest laryngeal cartilage - Made up of hyaline Cartilage - Consists of 2 laminae, which meet in the midline at the thyroid angle or Adam’s apple - The angle measures 90o in male and 120o females - There is oblique line on outer surface of each lamina for attachments: I. Sternothyroid muscle II. Thyrohyoid muscle III. Inferior constrictor muscle - Posterior borders of each lamina are drawn upward into a superior cornu and downward into inferior cornu - Posterior borders provide insertions to: I. Salpingopharyngeus muscle II. Palatopharyngeus muscle III. Stylopharyngeus muscle - posterior surface of the thyroid cartilage in the median plane provides attachment to: I. Thyroepiglittic Ligament II. Pair of Vestibular Ligament III. Pair of vocal Ligament Cricoid Cartilage - Shaped like a signet ring and lies below the thyroid cartilage, at the level of C6. - Made up of hyaline 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 - Posteriorly upper border of lamina articulates with base of the arytenoid cartilage - These joints are of synovial type NB: It is the only cartilage which completely encircles the larynx Epiglottis - Leaf shaped elastic cartilage - Situated behind the hyoid bone and base of the tongue - Its lower end is connected with the back of the thyroid cartilage, by the thyroepiglottic ligament - It is connected in front with the body of the hyoid bone - Sides of the epiglottis is connected to the arytenoid cartilages by aryepiglottic folds - Upper end is free and forms the upper boundary of laryngeal inlet - Anterior surface is connected to the tongue by medial and lateral glossoepiglotic folds - The depression on each side of the median fold – vallecula Arytenoid Cartilage - Two in number, pyramidal shaped - Situated at the back of the larynx - It is made up of mostly of hyaline cartilage - It has an apex, above which it supports the corniculate and cuneiform cartilages - Base articulates with lamina of cricoid cartilage - 2 processes project from the base I. Vocal Process – projects horizontally forward and gives attachment to the vocal ligament II. Muscular Process – project laterally and gives attachment to the posterior and lateral cricoarytenoid muscles Corniculate Cartilages (of Santorini) - two small nodules that articulate with the apex of the arytenoid cartilage - Lie in the posterior part of ary- epiglottic fold Cuneiform Cartilages (of Wrisberg) - two rod like pieces of cartilages that articulate with the corniculate cartilage - Lie in the posterior part of aryepiglottic folds just above the corniculate cartilages STRUCTURE OF LARYNGEAL CARTILAGES - Thyroid, cricoid and basal part of arytenoid cartilages are composed of hyaline cartilages and tend to ossify after 25 years of age and can be seen in radiographs - The apices arytenoid, corniculate and cuneiform cartilages are made up elastic cartilages and NOT ossify LARYNGEAL JOINTS - Includes paired crico-thyroid, crico- arytenoid and aryteno-corniculate joints Cricothyroid Joint - Between the inferior cornu of thyroid and side of cricoid cartilage - Plane synovial joint - Permits rotatory and gliding movements Cricoarytenoid Joint - Between the base of the arytenoid and lateral part of upper border of the lamina of cricoid cartilage - Plane Synovial Joint - Permits rotatory (to abduct or adduct the vocal cords) and gliding (to close or open the posterior part of glottis) movements Arytenocorniculate joint: - Between the arytenoid and corniculate cartilage - Plane synovial joint - No functional significance LIGAMENTS AND MEMBRANES I. Thyrohyoid Membrane - Extends from 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 - The lateral thyrohyoid ligament on each side contains a small nodule of elastic cartilage called cartilago-triticea - The thyrohyoid membrane is pierced by internal laryngeal nerve and superior laryngeal vessels, which lies beneath the mucous membrane of the larynx II. Quadrangular Membrane - Extends between the epiglottis and arytenoid cartilages - Its thickened lower margin forms the vestibular ligament  III. Cricotracheal Ligament - Connects the cricoid cartilage w/the first tracheal ring IV. Thyroepiglottic Ligament - Connects narrow lower end of epiglottis to the posterior surface of thyroid angle V. Hyoepiglottic Ligament - Connects posterior aspects of hyoid with the anterior surface of upper end of epiglottis VI. Cricothyroid Liagment - From the lower border of thyroid cartilage to the cricoid cartilage in the midline - Upper thickened border of cricothyroid ligament is called vocal ligament - Anterior end of each vocal ligament is attached to the deep surface of the thyroid angle, posterior end to the vocal process of the arytenoid cartilage. Laryngeal Cavity - Extends from inlet of larynx to the lower border of cricoid cartilage where it is continuous with the lumen of the trachea Laryngeal Inlet Boundaries - Anterior – epiglottis - Posterior – interarytenoid fold - On each side – aryepiglottic fold Laryngeal Cavity divided into 3 parts: - Vestibule or upper part - Ventricle or sinus of larynx/ middle part - Infraglottic compartment – lower part 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 Ventricle or sinus of larynx – middle part - Elliptical space between vestibular and vocal folds - The vocal folds are white and contain vocal ligament - Saccule of the larynx - narrow blind diverticulum of mucous membrane between the vestibular fold and lamina of thyroid cartilage. - Saccule of the larynx leads to sinus of the larynx - Saccule of larynx is provided with mucous glands, whose secretion lubricates the vocal cords – oil can of the larynx Rima Glottdis - Gap between the vocal folds in front and the vocal process of arytenoid cartilages behind - Lined by stratified squamous epithelium - Devoid of sub mucosa Infraglottic Compartment – lower part - Extends from vocal folds to the lower border of the cricoid cartilage - Its walls are formed by cricothyroid ligament and cricoid cartilage MUSCLE OF LARYNX Divided into - Extrinsic Muscles - Intrinsic Muscles Extrinsic Muscles - Includes elevators (suprahyoid) and depressors (infrahyoid) of larynx - Elevators: I. Digastric II. Thyrohyoid III. Stylohyoid  IV. Mylohyoid V. Geniohyoid - Depressors: I. Sternothyroid II. Sternohyoid III. Omohyoid Intrinsic muscles: I. Cricothyroid: Origin: side of the cricoid cartilage Insertion: lower border and inferior cornu of the thyroid cartilage Action: tenses vocal cords II. Posterior cricoarytenoid: Origin: back of cricoid lamina Insertion: muscular process of arytenoid cartilage Action: abducts the vocal cords III. Lateral cricoarytenoid: Origin: upper border of cricoid cartilage Insertion: muscular process of arytenoid cartilage Action: adducts the vocal cords IV. Transverse arytenoid: NB: The only unpaired muscle. 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 V. Oblique arytenoid: extends from the muscular process of one arytenoid cartilage to the vocal process of opposite arytenoid cartilage VI. Thyroarytenoid Origin: inner surface of thyroid cartilage Insertion: arytenoid cartilage VII. Vocalis It extends from the vocal process of arytenoid cartilage to the deep surface of thyroid angle Action: relaxes the vocal cords VIII. Aryepiglotticus Extends from the arytenoid cartilage to the side of epiglottis Action: close the laryngeal inlet IX. Thyroepiglotticus: Origin: medial surface of thyroid cartilage Insertion: lateral margin of the epiglottis Action: widens the inlet NB: The intrinsic muscles: By their action they alter the shape of inlet of larynx, rima vestibuli and rima glottidis. Muscles - Action 1. Cricothyroid cord - tenses the vocal  2. Posterior cricoarytenoid - opens the rima glottidis 3. Lateral cricoarytenoid - closes the rima glottidis 4. Transverse arytenoid - closes the rima glottidis 5. Oblique arytenoid - closes the rima glottidis 6. Thyroarytenoid - relax the vocal cord 7. Vocalis - relax the vocal cord 8. Thyepiglotticus - opens the inlet of the larynx 9. Aryepiglitticus - close the inlet of the larynx Muscles of the larynx develop from 4th – 6th pharyngeal arches, hence supplied by superior laryngeal and recurrent laryngeal nerves (braches of Vagus) NERVE SUPPLY OF THE LARYNX Sensory Supply - Up to the vocal folds (including the vocal fold): internal laryngeal nerve - - Below the vocal folds: recurrent laryngeal nerve Motor supply: - All intrinsic muscles supplied by recurrent laryngeal nerve - Exception: cricothyroid – external laryngeal nerve NB: Semon’s law – in progressive lesions of the recurrent laryngeal nerve the abductors of the vocal cords (posterior crico-arytenoids) are first to be paralysed and last to recover as compared to the adductors. This is because the nerve supplying the abductors are longer and has less thresh- hold, hence these branches are affected first. BLOOD SUPPLY AND LYMPHATIC DRAINAGE - Vocal folds and above: superior laryngeal vessels - Below the vocal folds: inferior laryngeal vessels - Lymph vessels drain into deep cervical lymph nodes RIMA GLOTTIDIS & PHONATION - Narrowest antero-posterior cleft of the laryngeal cavity Boundaries: - In front – angle of thyroid cartilage - Behind – interarytenoid folds of mucous membrane - On each side – vocal folds in the anterior three-fifth and vocal process of arytenoid cartilage in the posterior three-fifth Subdivisions: - Inter-membranous part – in the anterior three-fifth, between the vocal folds - Inter-cartilagenous part – in the posterior one-fifth, between the vocal process of arytenoid cartilage Shape of rima glottidis - Varies with the movements of the vocal cords In quiet breathing – - Intermembranous part is triangular - Intercartilagenous part is rectangular - As a whole the glottis is pentagonal In full inspiration - - The glottis widens and becomes diamond-shaped due to abduction of vocal cords During high pitched voice – - The rima glottidis is reduced to a linear chink due to adduction of both intermembranous part and intercartilagenous part During whispering – - Intermembranous part is highly adducted - Intercartilagenous part is separated by triangular gap - There by rima glottidis becomes inverted funnel shaped