larynx

Objectives Describe anatomical structure of larynx. Enlist the cartilages of the larynx. Define inlet of the larynx. Enlist the extrinsic and intrinsic muscles of the larynx with their nerve supply and actions.

larynx

larynx

larynx - The larynx is the organ of phonation (voice production) in addition to its respiratory function (air way). It is formed of a group of cartilages connected by Muscles, Ligaments and joints. Site: It lies below the hyoid bone in the midline of the neck at the level of C 4 - 6 vertebrae. Lateral view Anterior view

Structure The larynx consists of four basic components: A cartilaginous skeleton Membranes and ligaments Intrinsic and extrinsic muscles Mucosal lining The larynx is covered in front by the infrahyoid strap muscles and at the sides by the thyroid gland.

Cartilages of the Larynx Single cartilages Paired cartilages - Thyroid cartilage. - Arytenoid cartilage. - Cricoid cartilage. - Corniculate cartilage. - Epiglottic cartilage. - Cuneiform cartilage. All the cartilages, except the epiglottis, are of hyaline type. Epiglottis is formed of elastic cartilage The cartilages are: Connected by joints, membranes & ligaments Moved by muscles

1. Thyroid cartilage It consists of two laminae which are fused anteriorly to form the laryngeal prominence (Adam’s apple) but they are separated posteriorly. - Superiorly the area between the two laminae is called the superior thyroid notch. Superior cornu. Inferior cornu. Oblique line

2. Cricoid cartilage It is signet-ring in shape (it is the only complete cartilaginous ring in the upper respiratory airway). - It lies at the level of C. 6.

It articulates with the inferior cornu of the thyroid cartilage. Posteriorly articulates with the arytenoid cartilage. All these joints are synovial.

3. Epiglottis - It is leaf-shaped elastic cartilage which lies behind the tongue. - It has superior rounded free border and an inferior tapering end which is attached to the upper part of the thyroid notch.

4.Arytenoid cartilage It is pyramidal in shape. - The base articulates with the upper facet of the quadrate lamina of the cricoid cartilage.

5. Corniculate cartilage - It is a small cartilaginous nodule. - It articulates with the apex of each arytenoid and lies in the aryepiglottic fold. 6. Cuneiform cartilage - Small cartilaginous nodule which articulates with the upper surface of the corniculate cartilage and lies in the aryepiglottic fold , strengthening it

Ligaments and Membranes 1. Thyrohyoid membrane: - It connects the upper border of the thyroid lamina to the body and the greater horns of the hyoid bone.

2. Hyoepiglottic ligament - It is a small elastic ligament which connects the lower part of the anterior surface of the epiglottis to the hyoid bone.   3. Thyroepiglottic ligament - It is a small elastic ligament which connects the tapering lower end of the epiglottis to the inner surface of the thyroid cartilage.

Quadrangular membrane: Extends between the epiglottis and the arytenoid cartilages Its lower free margin forms the vestibular ligament that lies within the vestibular fold Cricothyroid membrane (conus elasticus): Lower margin is attached to upper border of cricoid cartilage Upper free margin forms vocal ligament

Inlet of the larynx Boundaries: a. Anterior: Upper edge of the epiglottis.(E) b. On each side: Aryepiglottic folds.(AEF) c. Posterior: Mucous fold between the arytenoids.(A)

Laryngeal Cavity Rima vestibuli Extends from laryngeal inlet to lower border of the cricoid cartilage Narrow in the region of the vestibular folds (rima vestibuli) Narrowest in the region of the vocal folds (rima glottidis) Divided into three parts: Supraglottic part, the part above the vestibular folds, is called the vestibule The part between the vestibular & the vocal folds, is called the ventricle Infraglottic part, the part below the vocal folds Rima glottidis A B C

Vocal Fold: The vocal fold (Vocal Cord) is a mobile fold on each side of the larynx and is concerned with voice production. It is formed by the mucous membranes covering the vocal ligament and is avascular and white in color. The vocal fold moves with respiration and its white color is easily seen when viewed with a laryngoscope. The gap between the vocal folds is called the rima glottidis or glottis.

Mucous Membrane The cavity is lined with ciliated columnar epithelium The surface of vocal folds, because of exposure to continuous trauma during phonation, is covered with stratified squamous epithelium Contains many mucous glands, more numerous in the saccule (for lubrication of vocal folds) Muscles Divided into two groups: Extrinsic muscles: divided into two groups Elevators of the larynx Depressors of the larynx Intrinsic muscles: divided into two groups Muscles controlling the laryngeal inlet Muscles controlling the movements of the vocal cords

Elevators of the Larynx The Suprahyoid Muscles Digastric Stylohyoid Mylohyoid Geniohyoid The Longitudinal Muscles of the Pharynx Stylopharyngeus Salpingopharyngeus Palatopharyngeus Depressors of the Larynx The Infrahyoid Muscles Sternohyoid Sternothyroid Omohyoid

Muscles of the Larynx I. Muscles acting on the laryngeal inlet = Muscles closing the laryngeal inlet: 1. Aryepiglottic muscles : Action: Closure of the laryngeal inlet. 2. Transverse arytenoid : Actions: (narrowing the laryngeal inlet) and adducts the vocal cords.  

3. Oblique arytenoids : Actions: They narrow the laryngeal inlet) and adducts the vocal cords.

II. Muscles acting on the vocal cords A: Muscles producing abduction of the vocal cords: * Posterior crico-arytenoid: - It is the ONLY abductor to the vocal cords Origin: Posterior surface of the lamina of the cricoid cartilage. Insertion: Muscular process of the arytenoid. Actions: - Abduction of the vocal cords.

B. Muscles producing adduction of the vocal cords 1. Lateral crico-arytenoid : Action: It draws the muscular process forwards so it rotates the vocal process inwards and adducts (closes) the vocal cords. 2. Transverse arytenoid 3. Oblique arytenoid

C. Muscles stretching (tensing) the vocal cords 1. Cricothyroid muscle - It lies on the outer surface of the larynx. Origin: Lateral aspect of the cricoid arch. Insertion: Into the inferior horn and lower border of the thyroid lamina. Actions: It draws the thyroid cartilage downwards and forwards, so it lengthens and tenses the vocal cords (responsible for the sharp loud voice).

D. Muscles relaxing the vocal cords 1. Thyroarytenoid muscle Actions: It shortens and relaxes the vocal cords, so it changes the pitch of the voice. 2. Vocalis muscle (it is the lower fibers of the thyro-arytenoid muscle) Action: Relaxation of the vocal cords.

Movements of the Vocal Cords Adductors Lateral cricoarytenoid Transverse arytenoid Abductor Posterior cricoarytenoid Movements of the Vocal Cords Adduction Abduction

Nerve supply A. Motor supply - All intrinsic muscles of the larynx are supplied by the “recurrent laryngeal nerve” EXCEPT cricothyroid which is supplied by the external laryngeal nerve. B. Sensory supply - Above the vocal cords ----------------- Internal laryngeal nerve (from vagus N). - Below the vocal cords ----------------- Recurrent laryngeal nerve (from vagus N).

Blood supply Blood supply: A. Arterial supply: 1. Above the vocal cords: Superior laryngeal artery (from the superior thyroid artery). 2. Below the vocal cords: Inferior laryngeal artery (from the inferior thyroid artery). B. Venous drainage: - It drains its venous blood into the corresponding superior and inferior thyroid veins respectively.

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