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Intrinsic Muscles of the Larynx

regulate valvular action of the laryngeal cavities; largely responsible for speech production; largely why you sound the way you do; situated on or within cartilaginous skeleton of larynx; form walls inside and partially outside larynx; largely responsible for the control of speech production.

Tensor muscles

intrinsic muscles whose purpose is tightening muscles

Adductor

muscle that draws a part toward the middle; bring together

Abductor

a muscle that draws a part away from the median line; pull apart

Cricothyroid muscle

-Intrinsic
-Tensor Muscle
-2 sections: vertical and oblique.
-Pull cricoid backward and upward and thyroid forward and downward.
-Increase length of vocal folds.
-Innervated by 10th cranial nerve.
-Unilateral vocal fold paralysis: Insult to nerve supply to one of the two muscles
-oblique portion won't pull cricoid posteriorly

Thyroarytenoid Muscle

-Intrinsic
-Tensor Muscle
-Makes up primary mass of the vocal fold (vocal cord)
-Runs from the thyroid cartilage to the arytenoid cartilage
-Runs parallel to glottis (opening between the vocal folds) -Attaches to vocal ligament and inserts on the vocal process of the arytenoid
Made up of 2 parts:
-Ventricularis (external thyroarytenoid)
-Vocalis (internal thyroarytenoid)

Ventricularis

a larger segment of thyroarytenoid muscle consisting of muscle fibers within the ventricular fold (wall of laryngeal ventricle)

Ventricularis Origin

lateral border of arytenoid cartilage

Ventricularis Insertion

lateral margin of epiglottis

Ventricularis Action

affects the ventricular folds

Vocalis

-Internal thyroarytenoid muscle
-Runs parallel to the vocal ligament
-Portion where internal central fibers run alongside vocal ligament
-5 Layer structure (described 2 ways)

Vocalis Origin

- medial inside border of thyroid cartilage (called macula flava anterior)

Vocalis Insertion

vocal processes of arytenoid cartilage

Thyroepiglotticus Muscle

-Intrinsic
-Tensor Muscle
• Muscle fibers run from thyroid cartilage upward in a vertical direction and end in aryepiglottic fold
• Serve as sphincter muscles of aditus
• Involved in closing entrance of larynx in swallowing
• Attach to deep surfaces of lamina of thyroid cartilage above attachment of thyroarytenoid muscle
• Attach to epiglottis--widens inlet into larynx

Aditus

Opening in the very top portion of the larynx above the vocal folds

Lateral Cricoarytenoid Muscle

-Intrinsic
-Adductor
• Arise from lateral borders of cricoid cartilage and insert into muscular processes at outside corners of each arytenoid cartilage.
• They adduct the arytenoids and squeeze the anterior tips of the vocal processes (and vocal ligament) tightly together.

Transverse Arytenoid Muscle

-Intrinsic
-Adductor
• Only intrinsic muscle that is not paired.
• Extends horizontally across the backs of the arytenoids.
• The fibers arise from the lateral margin and posterior surface of one arytenoid cartilage, course in a horizontal direction, and insert on the opposite arytenoid (Zemlin, 1998)
• Pulls middle edges of arytenoids together from bottom to top.

Oblique Arytenoid Muscle

An adductor Muscle. This extends from the muscular process of one arytenoid to the apex of the other. Action is to pull the upper tips of the arytenoids together.

Posterior Cricoarytenoid muscle

-Intrinsic
-Abductor
• Arise from the back wall of cricoid cartilage.
• Wraps around and Inserts into muscular processes of the arytenoid cartilages.
• They are the major muscles responsible for rocking and gliding the arytenoids apart.
• They are the major muscles that abduct the vocal folds.

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