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The Hyoid bone
- U shaped bone attached at the base of the tongue
- The laryngeal structure is suspended from it
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The Cricoid cartilage
- ‘Ring-like’ cartilage with an irregular shape in the posterior section
- Top cartilage of the trachea (windpipe)
- The foundation for the laryngeal structure
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The Thyroid cartilage (‘Adam’s Apple’)
- Prominent V shaped cartilage in the front of the throat
- Houses and protects the vocal folds
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The Arytenoid cartilages
- Two small pyramid shaped cartilages attached by ligaments atop the posterior end (back) of the cricoid cartilage
- They open and close the vocal folds
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The Epiglottis cartilage
- The leaf-shaped cartilage at the top of the thyroid cartilage
- Covers the top of the trachea (specifically – covers the glottis) when eating and drinking.
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There are two categories of muscles involved in laryngeal function
- Intrinsic muscles – both ends are attached inside the laryngeal structure
- Extrinsic muscles – one end is attached to the larynx and the other end is attached to some point outside of the larynx.
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The Thyroarytenoid muscles (Vocal folds)
There are two sets of vocal folds
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The upper set of vocal folds are referred to as either:
- The ventricular bands –OR-
- The false vocal chords
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The lower set of vocal folds are referred to as either:
- The vocalis muscles –OR-
- The Internal thyroarytenoids –OR-
- True vocal chords (vocal folds)
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The space between these upper and lower bands (true and false vocal folds) is called the ventricle and houses the lubricating glands for the vocal folds.
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The opening or space between the two (true) vocal folds is called the glottis or the glottic aperture – when it is open for normal breathing, this space forms a triangle, but when it is open for phonating (making sound) it forms a slit.
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The underside of the vocal folds is lined with a tough protective membrane called the
conus elasticus.
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The vocalis muscle makes up two thirds of the length of each vocalfold while the back third is cartilaginous, consisting of the vocal process of the arytenoid cartilage.
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When the vocal folds serve as a valve (for swallowing, coughing, lifting), both sets of chords (true and false) assist in closing the valve.
Only the true vocal folds are at work during phonation
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The Cricothyroid muscle
- Is attached to the criroid cartilage and the lower section of the thyroid cartilage.
- When it contracts, it pulls the thyroid cartilage forward and down
- This motion results in a lengthening of the thyroarytenoid muscles which helps in the production of higher tones when singing.
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The Cricoarytenoid muscles – two sets:
- The posterior cricoarytenoid muscles
- lateral cricoarytenoid muscles
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The posterior cricoarytenoid muscles
- Resist the forward pull on the arytenoids by the vocals muscle
- Open the vocal folds by pulling the vocal folds out to each side.
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The lateral cricoarytenoid muscles
bring the chords back together.
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The Arytenoid muscles –
There are three muscles in this interarytenoid group which “connect the arytenoid cartilages and are the primary factor in bringing the back end of the vocal folds together.
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The transverse arytenoid muscle –
forms a horizontal band across the back surface of the arytenoids cartilages and is the most important means of adducting the vocal folds.
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A pair of oblique arytenoid muscles
- form an X across the back of the arytenoids cartilages from the top of each down to the muscular process of the other.
- They assist the transverse arytenoids muscles in pulling the arytenoids cartilages together.
- They also function in the act of swallowing and in other valving actions of the larynx.
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The Supralayrngeal muscles originate above the larynx and are suspended from the hyoid bone. These muscles pull up on the laryngeal structure to:
- Aid in chewing and swallowing and are therefore also known as ‘the chewing and swallowing muscles’.
- Also aid in the tongue movements which control articulation.
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The Infralaryngeal muscles
pull down on the laryngeal structure and aid in yawning and inhaling. Therefore, they are known as ‘the yawning muscles’.
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The Constrictor muscles (upper, middle and lower)
- Muscles which line the throat and assist in swallowing by squeezing the food down toward and into the mouth of the esophagus.
- Because some of the muscles of the cricoid and thyroid cartilages merge with the lower constrictor muscle, the result is an important anchoring effect on the larynx during phonation.
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