Unit 5: Anatomy and physiology of Larynx

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Introduction What is this sound? What is Voice?

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Voice is sound created by voice box present in neck along with assistance from structures in throat & mouth. Unit 5: Study the anatomy & physiology and diseases of the larynx.

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Anatomy & Physiology of larynx Larynx, commonly called VOICE BOX Located in front, in the middle of the neck. Perched on the top of the trachea (windpipe).

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Location The position of the larynx in the neck varies with age, gender, head position and swallowing. The length of larynx is about 44 mm in an adult male and 36 mm in an adult female.

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Biological functions Protection of the airway Building intra-thoracic pressure for excretion and carrying out strenuous physical activities Non biological functions Speech Singing7

Anatomy of larynx Made of a bone, cartilages, muscles, membranes and joints. Hyoid bone supports larynx.

Front View

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Hyoid (Bone) U shaped single bone present above the thyroid cartilage. It is suspended from the tips of Styloid processes of the Temporal bones by Stylo-hyoid ligament.

It is not connected to any other bone directly. Hyoid bone is supported by many muscles & it can make variety of movements.

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Hyoid (Bone) Hyoid has 3 parts: a body and 2 pairs of horns. The 2 pairs of horns attach the Hyoid bone to the Thyroid cartilage.

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Ligament: Fibrous tissue that connects bones to other bones. Cartilage: Stiff yet flexible connective tissue found in many areas in the body, including the joints between bones. It is not as hard and rigid as bone but is stiffer and less flexible than muscle. Tendon: Tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments

NOTE: ligament vs. cartilage vs. tendon

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Cartilages 3 unpaired & 3 paired cartilages in larynx.Cartilage Epiglottis Thyroid Cricoid Arytenoids Number Location single single single paired Behind the hyoid bone and base of the tongue Front of the neck in the midline Above the trachea; below thyroid cartilage Rests on the back surface of cricoid cartilage Rests on the arytenoid cartilages Embedded in aryepiglottic folds

Corniculates paired Cuneiform paired

List of cartilages & location in larynx14

Epiglottis (Cartilage) It is leaf shaped cartilage. Attached to upper, inner surface of Thyroid. It attaches to Arytenoids at the back by the Quadrilateral membrane. The upper margins are formed by the Aryepiglottic folds.15

Epiglottis (Cartilage) Fn: Protects the wind pipe/ airway by deflecting food, water, saliva into trachea. It is open during breathing and closed during swallowing.

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Thyroid (Cartilage) Biggest cartilage in larynx present in front & sides. Protects voice box in the front. 2 laminas (quadrangular plates of cartilage-1 on right side & 1 on left side) Laminas join at midline to form the thyroid prominence (Adam s apple in men) - Felt or seen on surface of the neck in most men.17

Thyroid (Cartilage) 2 big horn-like structures (greater horns) to attach to the hyoid bone. 2 small horns (lesser horns) to attachment with Cricoid cartilage. Lesser horns attach Thyroid to Cricoid through the Cricothyroid ligament & Cricothyroid (CT) joints. CT joints are important for changing the pitch.

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Cricoid (Cartilage) It forms base of larynx . Attached to thyroid above through Cricothyroid ligament, Cricothyroid joints & trachea below by Cricotracheal ligament. Ring shaped cartilage Front surface is thin, narrow (called Arch) & back surface (known as Lamina) is broad, thick and wide. Arytenoids are present on the lamina of Cricoid19

Arytenoids (Cartilage) These are paired, pyramid shaped cartilages present on upper margins of lamina of Cricoid cartilage. Each Arytenoid has a base, an apex & 3 surfaces. Vocal process present on the medial surface is an important structure, because they form the posterior 1/3rd of true vocal folds.20

Arytenoids (Cartilage) Arytenoids are attached to the Thyroid in the front by Vestibular and Vocal ligaments. They are attached to Cricoid through the Cricoarytenoid ligaments & joints. These ligaments & joints are important for the opening & closing of vocal folds.21

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Corniculates & Cuneiform Corniculates: Small, paired, nodular structures perched on apex of each arytenoids. They may be 2 or even absent sometimes. Cuneiform: Small, paired, rod like structures present above the Corniculates. Present in a few individuals

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Joints/ ligaments of larynx Cartilages are connected to each other with the help of joints, muscles and membranes.

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Joints/ ligamentsCricothyroid ligament and joints Cricoarytenoid joints and ligaments Vestibular ligaments

ConnectsThyroid to Cricoid Cricoid to Arytenoid Arytenoids to Thyroid Arytenoids to Thyroid

ActionHelps in changing the pitch of voice Important for opening and closing of vocal folds Helps in changing the pitch of voice Helps in changing the pitch of voice

Vocal ligaments

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Anatomy of vocal folds The important structures responsible for producing voice (sound) are the vocal folds. There are 2 sets of vocal folds: Ventricular folds and True vocal folds. Their main function is protection of the lower airway.

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Ventricular folds/ False Vocal Folds They are pink in color & thick bands of mucous membranes with very few muscles, blood vessels & nerves. They start (originate) from the thyroid & attach (insert) to the arytenoids cartilages at the back through the Ventricular ligaments. They are not suited for voice production as they are bulky and do not have many muscles, blood vessels and nerves.28

True Vocal Folds/ Vocal folds They are present just beneath the Ventricular folds. They originate from the Thyroid cartilage, in the front and insert into the Arytenoid cartilages at the back through the Vocal ligaments. The true vocal folds are light pink in color but on laryngoscopy appear glossy white but the color changes in clinical conditions. The space between the true vocal folds is called the Glottis.29

True Vocal Folds/ Vocal folds VFs are made of mucous membranes, ligaments & muscles. ( blood vessels & nerve fibers) Under microscope, 5 different layers can be identified: 1. Epithelium 2. Superficial layer of Lamina propria (Reinke s space) 3. Intermediate layer of Lamina propria 4. Deep layer of Lamina propria 5. Vocalis muscle30

True Vocal Folds/ Vocal folds

Front view

Cross-section view31

True Vocal Folds/ Vocal folds Epithelium is the surface or the "skin" of the larynx and it is continuous with the lining of mouth, pharynx and trachea. Lamina propria has 3 distinct layers, each with a different consistency. The Intermediate layer and Deep layer of Lamina Propria forms the Vocal ligament.

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True Vocal Folds/ Vocal folds Superficial layer - a jelly-like substance, close to the surface Intermediate layer - an elastic, fibrous substance, like rubber bands Deep layer - a thread-like collagenous fiber layer Vocalis muscle is the main body of the vocal fold and very stiff.33

BLOOD SUPPLY TO LARYNX

Blood supply to Larynx Blood supply is derived from laryngeal branches of superior & inferior thyroid arteries and cricothyroid branch of the superior thyroid artery. (i) Superior thyroid artery arises from the external carotoid artery (ii) Inferior thyroid artery arises from thyrocervical trunk of the first part of the subclavian artery.

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Blood supply to Larynx (Contd.) On the left side, the thoracic duct is an important relation to the commencement of inferior thyroid artery. It lies in front of either the artery or the thyrocervical trunk, crossing them from medial to lateral side.36

Superior Laryngeal Artery The superior laryngeal artery arises from the superior thyroid artery. It passes deep to the thyrohyoid muscle and together with the internal branch of the superior laryngeal nerve, pierces the thyrohyoid membrane to supply the muscles and mucous membrane of the larynx and to anastomose with branches of its opposite side & with those of the inferior laryngeal artery.

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Inferior Thyroid Arteries The latter arises from the inferior thyroid artery at the level of the lower border of the thyroid gland and ascends on the trachea, together with the recurrent laryngeal nerve. It enters the larynx beneath the lower border of the interior constrictor muscle and supplies the muscles and mucous membrane.

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Cricothyroid Artery The cricothyroid artery passes from the superior thyroid artery, across the upper part of the cricothyroid ligament and anastomose with the branch of the opposite side.

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Veins The veins leaving the larynx accompany the arteries. The superior vessels enter the internal jugular vein by way of the superior thyroid or facial vein the inferior vessels drain by way of the inferior thyroid vein into the brachiocephalic veins. Some venous drainage from the larynx is by way of the middle thyroid vein into the internal jugular vein.

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Lymphatic drainage The part of the larynx above the vocal folds is drained by vessels which accompany the superior laryngeal vein, pierce the thyrohyoid membrane and empty into the upper deep cervical lymph nodes whereas the zone below the vocal folds drains, together with the inferior vein, into the lower part of the deep cervical chain often through the prelaryngeal and pretracheal nodes.41

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Membranes of larynxLaryngeal membranes Location Mucous membrane (Ciliated Columnar Present in the entire larynx Epithelium) Cricovocal membrane (Conus Elasticus) Originates from Cricoid cartilage and connects the Cricoid, Thyroid, and Arytenoid cartilages together. Inserts into the true vocal folds Connects Epiglottis and Thyroid to the Arytenoid cartilages at the back

Quadrangular membrane

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