SKELETAL STRUCTURE OF LARYNX
6 Cartilages: Cricoid ThyroidArytenoidCorniculateCuneiformEpiglottic
1 Bone:Hyoid
Basic Structure/Layers of Vocal Folds:EpitheliumLamina PropriaThyroarytenoid (Vocalis) Muscle
INTRINSIC LARYNGEAL MUSCLES: All Paired
Arytenoid MusclesInterarytenoids (transverse, oblique)
Thyroarytenoid MusclesCricoarytenoid Muscles (posterior, lateral)Cricothyroid Muscles
INTRINSIC LARYNGEAL MUSCLES: All inervated by recurrent laryngeal nerveExcept: Cricothyroids invervated by external
branch of superior laryngeal nerve
INTRINSIC MUSCLES: CLOSERS/ADDUCTORS
Lateral Cricoarytenoids (LCA)Interarytenoids (IA)
TransverseOblique
INTRINSIC MUSCLES: OPENERS/ABDUCTORSPosterior Cricoarytenoids (PCA)
Pull the arytenoids laterally to open the glottis
Pitch/Frequency of voiced sounds is largely controlled by varying the length of the vocal folds. As the folds are lengthened, their mass per unit length is reduced. Consequently, they vibrate faster when lengthened.
The vocal folds are attached to the thyroid cartilage at the front and the arytenoid cartilage at the back. The arytenoid cartilage, however, rides on the cricoid cartilage. So the length of the folds is mainly achieved by using the Cricothyroid (CT) Muscles, which rock the cricoid cartilage backward and upward, causing rotational movement of the thyroid cartilage (moving it slightly forward and tipping its front end downward). The cricothyroid muscles also pull the arytenoid cartilages slightly backwards, as they ride on the cricoid cartilage. These movements enabled by the cricothyroid muscles both lengthen and thin the vocal folds.
INTRINSIC MUSCLES: LENGTHENERS/THINNING
INTRINSIC MUSCLES: SHORTENERS/THICKENING
Shortening of the vocal folds occurs when the thyroarytenoid muscles (TA) contracts. When the thyroarytenoid muscles are not opposed by the thyrocricoid muscles (the lengtheners), they exert a shortening-thickening-laxing influence on the vocal fold cover tissues.
IMPORTANT TO REMEMBER:The Lengtheners/Shorteners and Openers/Closers all work in constant relationship to each other.
TO RECAP:
Openers/Abductors: PCACloser/Adductors: LCA & IALengtheners: CTShorteners: TA