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Related Competencies,  AN38.1 Describe the morphology, identify, , structure of the wall, nerve supply, blood, supply and actions of intrinsic and extrinsic, muscles of the larynx,  AN38.2 Describe the anatomical aspects of, laryngitis,  AN38.3 Describe anatomical basis of, recurrent laryngeal nerve injury

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Guidelines To Study Larynx, ,  Go through the slides.,  As it is vast topic you can subdivide them into four parts as, , , , , , , , , follows1st part- upto slide number 22, 2nd part- upto slide number 43, 3rd part- upto slide number 68, 4th part- Rest, After this you have to study larynx from any text book you, are following. Don’t worry about time at this stage of first, round of reading text book., After completion of these steps if you are not able to, understand any part feel free to communicate. Don’t jump, into any part without completing the whole process.

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Functions of Larynx,  It belongs to conducting part of respiratory tract. So it, , conducts respiratory air.,  It acts as a protective sphincter. It protects the trachea, , onwards respiratory tract by preventing entry of any, foreign body. So larynx is also called watchdog of, lungs.,  Larynx is the organ of phonation or production of, , voice.

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 It is located in midline of, front of neck.,  It extends from root of, , tongue at the level of, hyoid bone to trachea.,  Vertebral level- 3rd to 6th, cervical vertebrae,  Laryngo-tracheal junction, is at lower border of 6th, Cervical vertebra.,  Larynx belongs to lower, , respiratory tract., , Location

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Difference between male & female larynx,  Upto puberty there is no, , such difference between, male and female larynx.,  After puberty male larynx, , increases in size due to, growth of cartilages of, larynx.,  Adam’s apple or laryngeal, , prominence, is, more, pronounced, in, male.Thyroid angle is 90⁰, in male & 120⁰ in female.

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Constitution of larynx,  Skeletal framework made up of cartilages which are, , connected by joints, ligaments and fibroelastic, membrane.,  Muscles- Intrinsic muscles control mechanism of, , larynx,  Mucous membrane which lines inner surface larynx.

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Important Features, The largest cartilage of larynx., Hyaline in type., Consists of 2 quadrilateral laminae, each with 4 borders., Lower half of anterior borders of, both laminae meet at an angle open, posteriorly called thyroid angle., (90⁰ male and 120⁰ in female.), Projection on anterior surface of, thyroid angle is called laryngeal, prominence or adam’s apple., Upper part of anterior borders are, separated by thyroid notch., From postero-superior and posteroinferior angles of both the laminae, extend upwards and downwards 2, cornua called superior and inferior, cornu respectively.

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Thyroid cartilage

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Thyroid cartilage,  Membrane and ligament attachment, 1. Thyrohyoid membrane to superior border, 2. Cricothyroid membrane to lower border, 3. Lateral thyrohyoid ligament to superior cornu,  Muscles attached, 1. Insertion of sternothyroid, on, 2. Origin of thyrohyoid, oblique, 3. Origin of inferior constrictor of pharynx, line, 4. Stylopharyngeus, on posterior border, 5. Palatopharyngeus, of lamina, 6. Salpingopharyngeus

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Ligaments and membranes of larynx, Extrinsic, Thyrohyoid membrane, Hyoepiglottic ligament, Cricotracheal ligament, Intrinsic-They, interconnect, cartilages of larynx in, the form of fibroelastic lamina of, larynx., 1. Quadrate membrane, 2. Cricovocal membrane, , 1., 2., 3., 

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Quadrate Membrane-V.V.I., ,  It is more or less, , quadrangular in, appearance.,  Extends from arytenoid, cartilage to epiglottis, and thyroid cartilage in, front.,  Upper free border, raises the fold of mucous, membrane called, aryepiglottic fold.,  Lower free border, extending from, anterolateral surface of, arytenoid cartilage to, posterior surface of, thyroid lamina near, thyrid angle forms, Vestibular ligament.

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Cricovocal Membrane-V.V.I., ,  It is the conus elasticus, , component of cricothyroid, membrane.,  It extends from upper, margin of arch of cricoid, cartilage to central part of, lower border of lamina of, thyroid cartilage.,  Upper free border of, cricovocal membrane, extending from vocal, process of arytenoid, cartilage to posterior, aspect of thyroid angle is, called vocal ligament.

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Laryngeal cavity (coronal section through larynx), , • Cavity of larynx extends from inlet of larynx to lower border of, cricoid cartilage., • At inlet, oropharynx communicates with laryngeal cavity., • At lower border of cricoid cartilage, it is continuous with, trachea.

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Inlet of larynx,  Superior aperture of larynx., ,  Plane is oblique- downward and, , forward,  Anterior boundary-by upper, margin of epiglottis,  Posterior boundary-by, interarytenoid mucous folds, extending between 2, arytenoids,  Lateral boundary-by, aryepiglottic fold extending, from arytenoid cartilage to, lateral border of epiglottis.

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Inlet of larynx,  Beneath aryepiglottic fold lies aryepiglotticus muscle.,  During deglutition or swallowing the laryngeal inlet is, , closed.,  Lid like epiglottis does not fall back on inlet to close it, rather epiglottis is pulled downward & backward by, pull of aryepiglotticus muscle so that food bolus passes, smoothly on closed laryngeal inlet from oropharynx to, laryngopharynx.

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Functions of Inlet of Larynx

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Rima Glottidis (Glottis),  The narrowest antero-posterior cleft of laryngeal cavity., ,  Lined by non-keratinised stratified squamous epithelium.,  Devoid of submucous coat.,  Boundary, , ▪ Anterior-thyroid angle, ▪ Posterior-interarytenoid, , mucous fold, ▪ Lateral- Vocal fold in ant.3/5th,, ▪ Vocal process of arytenoid, in posterior 2/5th

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Vocal Cords or Vocal Folds, ,  Contains vocal ligament, , , , , , , , medially & vocalis muscle, laterally., Lined by nonkeratinised, stratified squamous, epithelium, Devoid of submucous tissue, Pearly white in colour, Vocal liganment is formed, by thickening of upper free, margin of cricovocal, membrane.

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Muscles of Larynx

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Intrinsic Muscle

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Cricothyroid muscle,  Cricothyroid is intrinsic muscle, , which is clearly visible from, surface.,  Origin- from outer surface of arch, of cricoid cartilage.,  Insertion, a) Posterior, oblique, fibresanterior aspect of inferior cornu, of thyroid cartilage., b) Anterior, vertical, fibresposterior part of lower border of, lamina of thyroid cartilage.

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Cricothyroid muscle, , , , , , , , , Nerve supply ****- All intrinsic muscles of larynx are supplied, by recurrent laryngeal nerve except cricothyroid which is, supplied by external laryngeal branch of superior, laryngeal nerve, a branch of vagus nerve (cricothyrod, develops from mesoderm of 4th pharyngeal arch)., Action-tilts lamina of thyroid cartilage downwards and, forwards around transverse axis passing through cricothyroid, joints of both sides., But another view is that cricoid rotates upward & backward., In both cases, it increases length of vocal cord which increases, tension of vocal cord., https://www.youtube.com/watch?v=BGX2dc75J_s

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Posterior Cricoarytenoid (CAP),  Origin-Posterior surface of, , lamina of thyroid cartilage, on either side of vertical, ridge.,  Insertion-On, posterior, surface of muscular process, of arytenoid cartilage of, same side.

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Action,  Action****- CAP rotates, , arytenoid cartilage, outward resulting in, abduction of vocal cord, giving rhomboid shaped, appearance of rima, glottidis.,  It is the only abductor of, vocal cord.,  So, it is called the safety, muscle of larynx.

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Lateral Cricoarytenoid,  Origin-From lateral, , part of upper margin, of arch of cricoid, cartilage.,  Insertion-Fibers pass, posterolaterally to be, inserted into anterior, aspect of muscular, process of arytenoid, cartilage.

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Action of Lateral Cricoarytenoid,  Action- Lateral, , cricoarytenoid rotates, vocal process medially, bringing tips of vocal, process together, closing, intermembranous part, of rima glottidis. This, action is known as, medial compression or, adduction of vocal, cord.

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Oblique Arytenoid,  These muscles of both sides, , cross obliquely with each other, along posterior aspect of, arytenoid cartilage.,  Origin-Back of muscular, process of one arytenoid, cartilage.,  Insertion-Apex of opposite, arytenoid cartilage. Beyond this, apex, the fibres are continued, deep to aryepiglottic fold as, aryepiglotticus.,  Action-closes laryngeal inlet.

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Transverse Arytenoid,  It is the only unpaired intrinsic muscle of larynx.,  It crosses midline.,  It lies deep to oblique arytenoid.,  It extends from posterior, , surface of one arytenoid to that, of other.,  It reduces the gap of the, intercartilaginous part of rima, glottidis.

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Thyroarytenoid,  It is a composite muscle.,  It extends among thyroid,, , arytenoid and epiglottis.,  Thyroarytenoid proper is, the central part of composite, muscle.,  It extends forward to back, of thyroid cartilage.,  It extends posteriorly, to anterolateral surface of, arytenoid.

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Thyroarytenoid,  Vocalis is prominent inferior margin, , , , , , , , , , of thyroarytenoid., It extends from vocal process of, arytenoid cartilage to thyroid angle., Its fibres lies lateral to vocal, ligament., Its anterior fibres extend posteriorly, from thyroid angle to vocal ligament., Its posterior fibres extend anteriorly, from vocal process to vocal ligament., Its contraction relaxes vocal cords ., It is antagonist to cricothyroid.

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Different Physiological, Positions of Rima Glottidis,  During forced breathing, ,  Both the parts are triangular,  Vocal cords are abducted

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Different Physiological Positions, of Rima Glottidis,  During normal, , phonation or speech,  Glottis is reduced, to narrow slit by, adduction of vocal, cords.

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Different Physiological, Positions of Rima Glottidis,  During Whispering,  Intermembranous, part of glottis is, , closed &, intercartilaginous, part becomes, wider with a, triangular gap.

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Lesion of Laryngeal nerves,  Both the motor nerves, , (external laryngeal for, cricothyroid) and recurrent, laryngeal nerve for all other, intrinsic muscles are, vulnerable to injury for the, following reasons Thyroid gland surgery,  Malignant changes in deep, cervical lymph nodes,  Bronchial or oesophageal, carcinoma or in case of, metastasis (secondary, deposits) of mediastinal lymph, nodes left recurrent laryngeal, nerve is affected.

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Lesion of Laryngeal nerves, Structure injured, , Muscles/structu, re paralysed, , Result, , External laryngeal, nerve, , Cricothyroid, , Weakness of voice due to, paralysis of cricothyroid that, increases tension of vocal cord, , Recurrent laryngeal, Nerve bilaterally, , Recurrent laryngeal, Nerve unilaterally, , Both the vocal, • Impairment of breathing due, cords (both are in to partial closure of glottidis, between, • Loss of speech, abduction &, adduction), Affected vocal, cord is in, between, abduction &, adduction, , Speech is not much affected as, the other normal cord, compensates and moves, towards affected vocal cord.