Intrinsic and Extrinsic Muscles of the Larynx

Overview of Intrinsic Muscles of the Larynx

The intrinsic muscles of the larynx are primarily responsible for sound production and vocal fold control.
They originate and insert on laryngeal cartilages, allowing for precise adjustments in vocal fold tension and position.
These muscles are categorized based on their effects on the glottis shape and vocal fold vibratory behavior: adductors, abductors, tensors, and relaxers.
Understanding these muscles is crucial for fields such as speech-language pathology, singing, and voice training.

Adductors: Muscles that bring the vocal folds together, essential for phonation.
Abductors: Muscles that separate the vocal folds, allowing for breathing.
Tensors: Muscles that stretch and tense the vocal folds, affecting pitch.
Relaxers: Muscles that reduce tension in the vocal folds, allowing for lower pitches.

Lateral Cricoarytenoid: Adducts the vocal folds by rotating the arytenoid cartilages medially.
Transverse Arytenoid: A unpaired muscle that pulls the arytenoids together, aiding in adduction.
Oblique Arytenoid: Works in conjunction with the transverse arytenoid to close the glottis during phonation.

Posterior Cricoarytenoid (PCA): The only muscle responsible for abducting the vocal folds, allowing for breathing.
Originates from the cricoid cartilage and inserts into the arytenoid cartilages, facilitating the opening of the glottis.

Cricothyroid: The primary tensor of the vocal folds, adjusting pitch by elongating the vocal folds.
Thyrovocalis: Part of the thyroarytenoid muscle, it tenses the vocal folds, contributing to pitch control.
Thyromuscularis: Acts as a relaxer, regulating tension and aiding in adduction when necessary.

Composed of two parts: Thyrovocalis (medial) and Thyromuscularis (lateral).
The thyrovocalis is crucial for maintaining the mass of the vocal folds and tensing them during phonation.
The thyromuscularis can relax the vocal folds when not opposed by other muscles, allowing for lower pitches.

Comprised of two parts: Pars Recta and Pars Oblique.
Pars Recta: Reduces the distance between the cricoid and thyroid cartilages, lengthening and tensing the vocal folds.
Pars Oblique: Slides the thyroid cartilage forward, contributing to pitch modulation.

Oblique Interarytenoids: Paired muscles that approximate the arytenoids, aiding in adduction.
Transverse Interarytenoid: A single muscle that also approximates the arytenoids, facilitating closure of the glottis during phonation.

Intrinsic Muscles: Control sound production and vocal fold adjustments; originate and insert within the larynx.
Extrinsic Muscles: Support the larynx and influence its position; originate outside the larynx and insert into it.

Intrinsic muscles control the tension and position of the vocal folds, directly affecting voice quality and pitch.
They work in pairs to achieve medial compression and longitudinal tension, essential for effective phonation.