Anatomy of larynx. anatomy and clinical importance

Reading of the slides needed

1. Anatomy of larynx and physiology of phonation Dr Rahul Mahato Lecturer ENT-HNS BMCTH

2. Introduction larynx lies in the middle and anterior part of neck Opposite the third to sixth cervical vertebrae During swallowing and phonation larynx moves in vertical and anteroposterior direction laryngeal crepitus: grating sensation produce by passive side to side movement of larynx In an adult, the larynx ends at the lower border of C6 vertebra.

3. LARYNGEAL CARTILAGES 3 unpaired thyroid, cricoid and epiglottis 3 paired cartilages arytenoid, corniculate and cuneiform

4. Types: Hyaline: Thyroid, cricoid and most of the arytenoid cartilage (except its tip) O ssification first in thyroid at the age of 25 years and later in cricoid and arytenoids, is complete by 65 years. Posterior view of larynx showing cartilages and ligaments

5. Types Elastic: epiglottis, corniculate, cuneiform and tip of arytenoids are fibroelastic in nature. They do not ossify. Other example of elastic cartilage is auricular cartilage. Fig: lateral view of larynx showing cartilages and ligaments

6. Thyroid Cartilage: largest laryngeal cartilage two alae, meet anteriorly in midline and form an angle (Adam’s apple) 90° in males and 120° in females. Vocal cords are attached in the middle of thyroid angle. Cricothyrotomy: Any airway obstruction above the vocal cord due to tumor or foreign body can be quickly, easily and effectively bypassed by piercing the cricothyroid membrane

7. Cricoid: ring shaped cartilage has narrow anterior arch and expanded posterior lamina, over which articulate arytenoids. Epiglottis: leaf-like, yellow, elastic cartilage forms anterior wall of laryngeal inlet. Petiole a stalk-like process of epiglottis attaches to the thyroid angle. Parts: anterior surface of epiglottis is attached to body of hyoid bone by hyoepiglottic ligament divides epiglottis into two parts suprahyoid and infrahyoid.

8. Pre-epiglottic space: Anterior surface of infrahyoid epiglottis is separated from thyrohyoid membrane and thyroid cartilage by fat filled pre-epiglottic space may be invaded by carcinoma of supraglottic larynx or the base of tongue.

9. Arytenoid cartilages: pyramidal shape has the following parts: Base : articulates with cricoid cartilage. Muscular process: provides attachment to intrinsic laryngeal muscles. Vocal process: provides attachment to vocal ligament of vocal cord. Apex: Superiorly it supports the corniculate cartilage in aryepiglottic fold.

10. Corniculate cartilage (of Santorini): articulates with the apex of arytenoids cartilage. Cuneiform cartilage (of Wrisberg): rod shaped cartilage situated in front of corniculate cartilage in the aryepiglottic fold.

11. Joints: Cricoarytenoid joint: synovial joint formed between the base of arytenoid and a facet on the upper border of cricoid lamina. Two types of movements :rotatory and gliding. rotatory movement occurs at a vertical axis and abducts or adducts the vocal cord. Arytenoids glide laterally and medially and help in closing or opening the posterior part of glottis. Cricothyroid joint: synovial joint formed between the inferior cornua of thyroid cartilage and a facet on the cricoid cartilage.

12. Membranes & Ligaments Extrinsic: connect thyroid cartilage & epiglottis with hyoid bone; cricoid cartilage with trachea. Intrinsic: connect cartilages of larynx to each other.

13. EXTRINSIC MEMBRANES AND LIGAMENTS Thyrohyoid membrane : thyroid cartilage to hyoid bone. pierced by superior laryngeal vessels and internal laryngeal nerve. Cricotracheal membrane: cricoid cartilage to the first tracheal ring. Hyoepiglottic ligament: epiglottis to hyoid bone

14. INTRINSIC MEMBRANES AND LIGAMENTS Cricovocal membrane. triangular fibroelastic membrane. upper border is free and stretches between middle of thyroid angle to the vocal process of arytenoid forms the vocal ligament lower border attaches to the arch of cricoid cartilage. From its lower attachment the membrane proceeds upwards and medially and forms conus elasticus subglottic foreign bodies sometimes get impacted. Quadrangular membrane. lies deep to mucosa of aryepiglottic folds not well-defined. stretches between the epiglottic and arytenoid cartilages. lower border forms the vestibular ligament which lies in the false cord.

15. Cricothyroid ligament : anterior part of cricothyroid membrane is thickened to form the ligament and lateral part forms the cricovocal membrane. Thyroepiglottic ligament: It attaches epiglottis to thyroid cartilage.

16. Intrinsic muscles Acting on vocal cords Abductors : Posterior cricoarytenoid Adductors : Lateral cricoarytenoid , Interarytenoid (transverse arytenoid) and Thyroarytenoid (external part) Tensors : Cricothyroid Vocalis (internal part of thyroarytenoid) Acting on laryngeal inlet Openers of laryngeal inlet : Thyroepiglottic (part of thyroarytenoid) Closers of laryngeal inlet : Interarytenoid (oblique part) Aryepiglottic (posterior oblique part of interarytenoids)

17. Extrinsic muscles: connect the larynx to the neighbouring structures. divided into elevators or depressors of larynx. Elevators: Primary elevators act directly( as they are attached to the thyroid cartilage) include stylopharyngeus, salpingopharyngeus, palatopharyngeus and thyrohyoid. Secondary elevators act indirectly (as they are attached to the hyoid bone) include mylohyoid (main),digastric, stylohyoid and geniohyoid. Depressors: sternohyoid, sternothyroid and omohyoid.

18. Table: Origin insertion and actions of intrinsic laryngeal muscles

19. Laryngeal cavity 1. Laryngeal inlet 2. Laryngeal Vestibule 3. Laryngeal Ventricle 4. Rima glottis 5. Subglottis

20. Pediatric Larynx Conical in shape & subglottis is narrowest part Positioned high (C3-C4) Moves higher during swallowing allowing simultaneous breathing & feeding Loose sub-mucosal tissues (swell up easily) Soft cartilages that collapse easily

21. Oncological Divisions A. Supraglottis: laryngeal inlet to apex of ventricle B. Glottis: apex of ventricle to 10 mm below C. Subglottis: lower glottic border to lower cricoid border

22. Subsites Supraglottis: 1. Epiglottis 2. Aryepiglottic folds 3. Ventricular bands 4. Laryngeal ventricle B. Glottis: 1. True vocal cords 2. Anterior commissure 3. Posterior commissure C. Subglottis

23. Mucous Membrane Stratified squamous epithelium: Epiglottis (anterior surface + upper half of posterior surface), upper part of aryepiglottic folds & vocal cords Pseudo-stratified ciliated columnar (respiratory) epithelium: Rest of laryngeal mucous membrane

24. Nerve Supply Superior Laryngeal Nerve: Internal: sensation to supraglottis & glottis External: motor to cricothyroid muscle Recurrent Laryngeal Nerve: sensation to subglottis motor to all intrinsic muscles but cricothyroid Fig:Nerves supplying the larynx and their relations especially with arteries

25. Blood Supply Arterial supply: Laryngeal br. of superior & inferior thyroid Venous drainage: Superior thyroid vein → internal jugular vein Inferior thyroid vein → innominate vein

26. Lymphatic Drainage Supraglottis: via thyrohyoid membrane into upper deep cervical nodes & thyroid gland Subglottis: via cricothyroid membrane into pretracheal + lower deep cervical nodes Glottis: has no lymphatics

27. Functions of Larynx 1. Protection of lower airway 2. Phonation (voice production) 3. Passage of air into lungs for respiration 4. Chest fixation by glottic closure

28. 1. Protection of lower airway Larynx protects the lower respiratory tract in following ways: Sphincteric closure of laryngeal opening : During swallowing food entry into air passage is prevented by the closure of three successive sphincters, so no food or vomitus can enter the larynx. The sphincters are: Laryngeal inlet False cords True cords

29. Cessation of respiration : When food meets the oropharynx reflex generated by afferent fibers of ninth nerve ceases the respiration temporarily. Cough reflex : Coughing dislodges and expels any foreign particle that meets respiratory mucosa. Larynx acts as a watchdog of lungs and immediately starts “barking” at the entry of any foreign body.

30. 2. Phonation (voice production) Aerodynamic myoelastic theory of voice production : Like a wind instrument, larynx produces voice. Speech : three phases in the production of speech: pulmonary laryngeal and supraglottis/oral

31. Pulmonary phase : creates energy flow with inflation of lungs and expulsion of air provides a column of air to the larynx. subglottic air pressure is generated by the exhaled air from the lungs with the help of contraction of thoracic and abdominal muscles. Laryngeal phase : Vocal folds vibrate to create sound that is then modified in the next phase. The air pressure opens the adducted cords and small puffs of air are released. Vocal folds are adducted and pressure of moving air causes vibrations of the elastic vocal folds Supraglottic/oral phase : Considered a unique individual sound. Words of the sentences are formed by the muscles of pharynx, tongue and lips and teeth. vibration of the vocal cords produces sound, which is amplified by mouth, pharynx, nose and chest. modulator action of lips, tongue, palate, pharynx and teeth converts the sound into speech.

32. 3. RESPIRATION Larynx regulates flow of air into the lungs. Vocal cords abduct during inspiration and adduct during expiration. 4. FIXATION OF THE CHEST Closure of glottis helps in raising intra-thoracic & intra-abdominal pressure required for: digging, pulling and climbing. Coughing, vomiting, defaecation, micturition and childbirth also require a fixed thoracic cage against a closed glottis.

33. Embryological development of larynx