Anatomy of the Larynx (PDF)

Anatomy of the Larynx Ms Athi Baliso CABA, HUB Office 4.10.1 [email protected] Lecture Outline Anatomy of the larynx – its location, structure, vasculature, innervation and clinical relevance Anatomical Position & Relations o Located in the anterior compartment of the neck, suspended from...

Anatomy of the Larynx Ms Athi Baliso CABA, HUB Office 4.10.1 [email protected] Lecture Outline Anatomy of the larynx – its location, structure, vasculature, innervation and clinical relevance Anatomical Position & Relations o Located in the anterior compartment of the neck, suspended from the hyoid bone, between C3 and C6 o Continuous with the trachea inferiorly and opens into the laryngopharynx superiorly  Consists of a cartilaginous skeleton Anatomical Structure connected by membranes, ligaments and muscles Anatomical Structure Laryngeal cartilages Cricoid cartilage o Inferior aspect of the larynx and is connected to the trachea inferiorly o Attached to inferior border of the thyroid cartilage via cricothyroid ligament o Attached to first tracheal ring via cricotracheal ligament Laryngeal cartilages Thyroid cartilage o Formed by left and right lamina, which join anteriorly to form the laryngeal prominence (Adam’s apple) o Posterior border of laminae project superiorly and inferiorly to form the superior and inferior horns (also known as cornu) Superior horns are connected to the posterior end of the greater horn of the hyoid bone via the lateral thyrohyoid ligament Inferior horns articulate with the cricoid cartilage o Oblique line (ridge on lateral surface of lamina) – ends of the expand to form superior and inferior thyroid tubercles Laryngeal cartilages Epiglottis o Attached by its stem to inner aspect of angle formed by laminae of the thyroid cartilage via the thyro-epiglottic ligament in the midline o Attached to the hyoid bone by the hyo- epiglottic ligament o Sits above the laryngeal inlet, during swallowing, as the larynx moves up and forward, swings downward to close off the laryngeal inlet, preventing food and liquids from entering the respiratory tract  Laryngeal cartilages Arytenoid cartilages o Apex – articulates with a corniculate cartilage o Base – articulates with the superior border of the cricoid cartilage o Anterolateral surface has two depressions for attachment of the vocalis muscles and vestibular ligament o Vocal process – attachment for the vocal ligament o Muscular process – attachment for the posterior and lateral cricoarytenoid muscles Laryngeal cartilages Corniculate cartilages o Articulate with the apices of the arytenoid cartilages Cuneiform cartilages o Located within the aryepiglottic folds, no direct attachment, but act to strengthen the folds Extrinsic ligaments Thyrohyoid membrane o Tough fibro-elastic ligament o Between the superior margin of the thyroid cartilage and the hyoid bone o Aperture laterally for laryngeal vessels and nerve o Median thyrohyoid ligament – Anteromedial thickening of the membrane. o Lateral thyrohyoid ligaments – Posterolateral thickenings of the membrane Intrinsic ligaments Fibro-elastic membrane Connects the laryngeal cartilages and completes the architectural framework of the laryngeal cavity o Cricothyroid ligament – Originates from the cricoid cartilage and extends superiorly, where it terminates with a free (unattached) upper margin – which forms the vocal ligament (under the vocal fold) Attached anteriorly to the thyroid cartilage, and posteriorly to the arytenoid cartilage Thickened anteriorly in the midline to form a distinct median cricothyroid ligament Intrinsic ligaments Fibro-elastic membrane o Quadrangular membrane – Between the anterolateral arytenoid cartilage and the lateral aspect of the epiglottis; also attached to the corniculate cartilage Free upper and lower margin (thickened to become the vestibular ligament – under the vestibular fold) Laryngeal Folds Vocal Folds o Two bands of smooth muscle tissue o Under the control of the muscles of phonation, they are abducted, adducted, relaxed and tensed to control the pitch of the sound created o Opening between them (Rima glottis)  Vestibular Folds o Superior to the true vocal cords Laryngeal o Consist of the vestibular ligament (free lower edge of the quadrangular membrane) Folds covered by a mucous membrane o Fixed folds – protect the larynx o Opening between them – Rima vestibuli Laryngeal joints Synovial; each is surrounded by a capsule and reinforced by associated ligaments Cricothyroid joints o Between the inferior horns of the thyroid cartilage and the cricoid cartilage o Enable the thyroid cartilage to move forward and rotate downward on the cricoid cartilage – lengthens and puts tension on the vocal ligaments  Laryngeal joints Crico-arytenoid o Between articular facets on the superolateral surfaces of the cricoid cartilage and the bases of the arytenoid cartilages o Enable the arytenoid cartilages to slide away or toward each other and to rotate so that the vocal processes pivot either toward or away from the midline – abduct and adduct the vocal ligaments Movements of the crico-arytenoid joints Cavity of the larynx Lined with mucosa, extends from its superior opening (laryngeal inlet) to the inferior border of the cricoid cartilage which is continuous with the the trachea o Vestibule – between the laryngeal inlet and the vestibular folds (false vocal cords) o Middle part – between the vestibular folds and the vocal folds, contains vocal cords o Infraglottic space – between vocal folds and the inferior opening of the larynx (is continuously open) Cavity of the larynx Laryngeal Muscles Extrinsic muscles o Comprised of the suprahyoid and infrahyoid groups, and the stylopharyngeus (a muscle of the pharynx) – elevate or depress the larynx during swallowing Intrinsic muscles o Act on the individual components of the larynx, they control the shape of the rima glottidis and the length and tension of the vocal folds – playing a vital role in breathing and phonation o All (except the cricothyroid) are innervated by the inferior laryngeal nerve – the terminal branch of the recurrent laryngeal nerve, itself a branch of the vagus nerve; cricothyroid is innervated by the external branch of the superior laryngeal nerve – again derived from the vagus nerve Intrinsic muscles Cricothyroid muscle o Attachments: Originate from the anterolateral aspect of the cricoid cartilage and insert to the inferior margin (straight part) and inferior horn of the thyroid cartilage (oblique part) o Actions: Forward and downward rotation of thyroid cartilage at cricothyroid joint – stretches and tenses the vocal ligament Intrinsic muscles Posterior crico-arytenoid muscles o Attachments: Originates from a large shallow depression on the posterior surface of the lamina of the cricoid cartilage and attaches to the muscular process of the arytenoid cartilage o Actions: Abduction and lateral rotation of the arytenoid cartilage = opening the rima glottidis Intrinsic muscles Lateral crico-arytenoid muscles o Attachments: Originates from from the upper surface of the arch of the cricoid cartilage and inserts on the muscular process of the arytenoid cartilage o Actions: Internally rotate and abduct the arytenoid cartilages = abducted vocal folds with an open-air channel posteriorly between the arytenoid cartilages Intrinsic muscles Transverse arytenoid o Attachments: Lateral border of posterior surface of arytenoid cartilage and inserts on lateral border of posterior surface of adjacent arytenoid cartilage o Actions: Adduction of the arytenoid cartilages  Oblique arytenoid muscles o Attachments: Posterior surface of muscular process arytenoid cartilage and attaches on posterior surface of Intrinsic muscles apex of opposite arytenoid cartilage; extends into aryepiglottic fold o Actions: Sphincter of the laryngeal inlet Intrinsic muscles Vocalis o Attachments: Lateral surface of vocal process of the arytenoid cartilage and insert along the length of the vocal ligament and thyroid angle o Actions: Adjusts tension in the vocal folds Intrinsic muscles Thyro-arytenoid muscles o Attachments: Originates from the thyroid angle & opposite cricothyroid ligament and attaches to the anterolateral part of the arytenoid cartilage o Actions: Sphincter of vestibule and of laryngeal inlet, relaxes the vocal ligament Intrinsic muscles Functions: o Adjust tension in the vocal ligaments o Open and close the rima glottidis o Control the inner dimensions of the vestibule o Close the rima vestibuli o Facilitate closing of the laryngeal inlet Achieve these by: o Acting on the cricothyroid and crico-arytenoid joints o Adjusting the distance between the epiglottis and arytenoid cartilages o Pulling directly on the vocal ligaments o forcing soft tissues associated with the quadrangular membranes and vestibular ligaments toward the midline Blood supply Superior laryngeal artery, a branch of the superior thyroid branch of the external carotid artery ✷ Accompanies the internal branch of the superior laryngeal nerve through the thyrohyoid membrane to reach the larynx Inferior laryngeal artery, a branch of the inferior thyroid branch of the thyrocervical trunk of the subclavian artery ✷ Enters the larynx by passing deep to the margin of the inferior constrictor muscle Venous drainage Drained by corresponding veins i.e., o Superior laryngeal veins ➞ superior thyroid veins ➞ internal jugular veins o Inferior laryngeal veins ➞ inferior thyroid veins ➞ left brachiocephalic vein Innervation o Motor and sensory innervation – superior and inferior laryngeal nerves and and recurrent laryngeal nerves which are branches of the vagus nerve (CN X) o Each superior laryngeal nerve divides into the internal and external laryngeal nerves o Internal laryngeal nerve provides the sensory and autonomic innervation of the laryngeal cavity to the level of the vocal cords o Recurrent laryngeal nerves continue toward the larynx as the right and left inferior laryngeal nerves – provide motor innervation to all the intrinsic muscles of the larynx except the cricothyroid muscles; and sensory innervation to the laryngeal cavity below the vocal cords Vocal Cord Paralysis o Vocal cords movement is controlled by the intrinsic muscles of the larynx o Vocal cord paralysis – causes the loss of control of the muscles that control the voice – due to its long course, the recurrent laryngeal nerve is susceptible to damage o Causes of RLN palsy include apical lung tumour, thyroid cancer, aortic aneurysm, cervical lymphadenopathy or iatrogenic (particularly during thyroid surgery due to the close relationship with the inferior thyroid artery) Unilateral RLN palsy - one vocal cord is paralysed, the other compensates, and speech is not affected to a great degree Bilateral palsy – both vocal cords are paralysed in a position between adduction and abduction, breathing is impaired, and phonation cannot occur Treatments for vocal fold paralysis are voice therapy and surgery Laryngoscopy Use to examine your larynx – performed with a laryngoscope, a thin tube with a light, lens and a video camera that helps look closely at your larynx Evaluate patients with difficulty swallowing, assessment of the vocal cords, and assessment of the larynx for tumors, masses, and weak voice Direct laryngoscopy – the tongue and epiglottis are held forward, allowing direct inspection of the larynx Other methods of inspection include the passage of fiberoptic endoscopes through either the oral cavity or nasal cavity Laryngoscopy https://www.youtube.com/watch?v=UnjhyYedm8Q&pp=ygURTGFyeW5nb3Njb3B5IGRlbW 8%3D https://www.youtube.com/watch?v=zhulVe3sO0&pp=ygURTGFyeW5nb3Njb3B5IGRlbW8% 3D Cricothyroidotomy o An emergency procedure to provide a temporary airway o Typically used in situations where there is an obstruction at or above the larynx (e.g foreign body, angioedema or facial trauma), and intubation has been unsuccessful o To perform the technique, the thyroid cartilage is palpated in the neck – below which there is a depression representing the cricothyroid ligament o A small incision is made in the midline of this ligament, and an endotracheal tube is inserted to secure the airway  o A surgical procedure in which a hole is made in the trachea and a tube is inserted to enable ventilation o Generally performed when there Tracheostomy is obstruction to the larynx because of inhalation of a foreign body, severe oedema secondary to anaphylactic reaction, or severe head and neck trauma Questions???