Voice Disorders Lecture 3.pdf

SLP 286 – Voice Disorders Presentation 3 Dr. Ahmed Nagy Associate Professor , Department of Speech and Language Pathology UAEU Muscles of the Larynx Divided into two groups and each group is further divided into two subgroups: 1. Extrinsic muscles {also called strap muscles because of their flat s...

SLP 286 – Voice Disorders Presentation 3 Dr. Ahmed Nagy Associate Professor , Department of Speech and Language Pathology UAEU Muscles of the Larynx Divided into two groups and each group is further divided into two subgroups: 1. Extrinsic muscles {also called strap muscles because of their flat shape}: divided into two subgroups A. Elevators of the larynx (suprahyoid muscles) B. Depressors of the larynx (infrahyoid muscles) 2. Intrinsic muscles: divided into two subgroups A. Muscles controlling the laryngeal inlet B. Muscles controlling the movements of the vocal Folds • Muscular nomenclature is usually very informative - a muscles name is composed of the origin and insertion • Ex. Sternohyoid is a muscle that extends from the sternum to the hyoid bone • Another conclusion can be made on action - the action of a muscle is that the insertion is moved closer to the origin when this muscle is activated • Ex. the sternohyoid makes the Hyoid move closer to the sternum • We can conclude from the name that the sternohyoid brings the hyoid down in the direction of the sternum Laryngeal Elevation A- Muscles inserted into the hyoid originating in higher structures, thus elevating the hyoid which is impacting laryngeal altitude through the thyrohyoid membrane and ligaments (4 muscles) B- The larynx is connected to the pharynx via the laryngo-pharyngeal opening; when the pharynx is elevated, the larynx is elevated (These muscles will be studied with the muscles of the pharynx ) Digastric - Anterior belly from mandible digastric fossa {V} - Posterior belly from mastoid process of temporal bone {VII} - Both bellies connected through intermediate tendon looped into a fibrous loop on the hyoid bone - Contributes to upward and forward hyoid excursion & laryngeal elevation Stylohyoid Origin: Styloid process of temporal bone Insertion: Hyoid bone Innervation: VII Action: elevates hyoid upwards and backwards Mylohyoid fibrous raphe Mylohyoid Mylohyoid line Origin: Mylohyoid line on the inner surface of the mandible Insertion: Meets opposite muscle in the midline of the floor of the mouth to form mylohyoid fibrous raphe - The raphe extends from the inner surface of the mandible to the hyoid bone Innervation: V Action: Provides stability for tongue movement during swallowing, contributes to hyoid elevation and mandibular depression when hyoid is fixed Geniohyoid Genial tubercle geniohyoid Origin: from genial tubercle of mandible Insertion: front of hyoid bone Innervation: C1 Hitchhiking on XII Action: Elevation and forward traction on the hyoid bone Laryngeal Depression Muscles inserted into the hyoid originating in lower structures, thus depressing the hyoid which is impacting laryngeal altitude through thyrohyoid membrane and ligaments OR muscles inserted directly into thyroid cartilage Sternothyroid Origin: Sternum Insertion: Thyroid cartilage lamina Innervation: C1-C3 via XI Action: Depress the hyoid bone and thyroid cartilage Thyrohyoid Origin: Oblique line of thyroid cartilage Insertion: Body of hyoid bone Innervation: C1-C3 via XI Action: Depress hyoid bone; in some texts considered a laryngeal elevator if contracted while the hyoid is fixed because in this condition the thyroid cartilage is elevated Sternohyoid Origin: manubrium and clavicle Insertion: body of hyoid bone Innervation: C1-C3 via XI Action: depress the hyoid bone Omohyoid Sternocleidomastoid (SCM) Origin: The muscle is made of two bellies: • Superior: inferior border of hyoid • Inferior: upper border of scapula Insertion: both bellies connected by an intermediate tendon, deep to SCM. The intermediate tendon is attached to the clavicle by fibrous fascia Innervation: C1-C3 via XI Action: Depress and retract the Hyoid bone The Glottis • The space between the two vocal folds is called the glottis • The anterior segment is between the two vocal folds, it is called the Anterior Glottis/Membranous Glottis • The posterior segment is between the two arytenoid cartilages, it is called the Cartilaginous Glottis/Posterior Glottis • Both segments of the glottis must be closed during swallowing, the membranous glottis must be closed for phonation https://petersenvoicestudio.com/2014/07/24/coup-de-glottemembraneous-and-cartilaginous-adduction/ Movements of the Vocal Folds • Adduction • Abduction Glottis (space between folds) Folds closed (adducted) Folds open (abducted) (View from above) Closure of the Membranous Glottis The lateral cricoarytenoid. From the upper border of the lateral part of Cricoid cartilage to the front of the arytenoid cartilage. This moves the vocal processes of both arytenoids towards the midglottic plane, closing the Membranous Glottis. Closure of the Cartilaginous Glottis 1- The Transverse Arytenoid: Muscle fibers arise from the posterior surface of each arytenoid, cross over and insert in the posterior surface of the other arytenoid . When it contracts, it brings the bases of the arytenoids together, closing the cartilaginous glottis. 2- The Oblique Arytenoid: From the base of each arytenoid to the apex of the other. When it contracts it brings the apices of the arytenoids together, also contributing to the closure of the cartilaginous glottis. THE ONLY ABDUCTOR OF THE VOCAL FOLD/Glottis Opener The Posterior Cricoarytenoid Muscle: Originates from the posterior surface of the cricoid lamina to the back of the arytenoid. Its action opens both the membranous and cartilaginous segments of the glottis Muscles Controlling the Laryngeal Inlet There are 2 oblique arytenoid muscles. Each originates from the base of one of the two arytenoids and is inserted into the apex of the other arytenoid. After insertion the fibers continue into the mucosa of the aryepiglottic fold as the aryepiglottic muscle. Both are intrinsic laryngeal muscles innervated by the recurrent laryngeal branch of the Vagus. When contracting, these 4 muscles bring the arytenoids and the aryepiglottic folds closer to each other, thus narrowing the laryngeal inlet. Muscle Increasing the Length & Tension of the Vocal Folds The Cricothyroid Muscle: There are two sets of fibers: 1. The vertical fibers from the anterolateral surface of the cricoid to the inferior border of the thyroid cartilage 2. The oblique fibers from the anterolateral surface of the cricoid to the inferior horns of thyroid cartilage Both sets of fibers simultaneously contract. This brings the lower border of thyroid closer to arch of the cricoid, shutting down the cricothyroid space {occupied by the cricothyroid membrane} like a helmet visor. The distance between the thyroid angle anteriorly and the arytenoid vocal process is increased; the vocal ligament and the covering mucosa are stretched “ like a guitar string”. This leads to higher pitch. Muscle Decreasing the Length & Tension of the Vocal Cords • The thyroarytenoid muscle originates from the thyroid and inserts in the vocal process and anterolateral surface of the arytenoid. Lateral to the vocal ligament, the muscle is a broad sheet; however, medially, the muscle is thin and is called the vocalis and is attached to the vocal ligament . • Contraction draws insertion closer to origin {the base of the arytenoid slides forward on the lamina of the cricoid}, shortening the vocal fold ligament, laxing the covering mucosa {reducing tension}, leading to a lower pitch. • There is a variability in the level of neurogenic control over the vocalis segment of the thyroarytenoid muscle. Some people can control how much of the longitudinal length of their vocal ligament and covering mucosa is involved in the phonatory mucosal vibration Blood Supply and Lymph Drainage Arteries: • Upper half: Superior laryngeal artery, branch of superior thyroid artery • Lower half: Inferior laryngeal artery, branch of inferior thyroid artery Veins: • Accompany the corresponding arteries Lymphatics: • The lymph vessels drain into the deep cervical lymph nodes The Midway boundary is the Glottis The vagus nerve provides sensory and motor innervation to the larynx through its different branches: Arising from the inferior vagal ganglion is the superior laryngeal nerve and the main stem of the vagus on each side A- The superior laryngeal nerve divides into two branches: 1. The internal laryngeal nerve piercing the thyrohyoid membrane entering the laryngeal cavity providing sensory innervation to the mucosa to the from the inlet to the glottis 2. The external laryngeal nerve: Motor to the cricothyroid muscle B- From the main stem of the vagus, a recurrent laryngeal nerve is dedicated to the larynx . On the right side it arches around the right subclavian artery in the neck, on the left it arches around the more distal arch of the aorta in the thorax Each recurrent laryngeal provides motor innervation to all intrinsic laryngeal muscles EXCEPT the cricothyroid and provides sensory to the mucosa from the subglottic area to the glottis Thank You