The posterior muscles of the voice refers to:
(1)transverse arytenoid muscle
(2)oblique arytenoid muscle
(3)posterior cricoarytenoid muscle
(All of these muscles are located in the back of the thyroid cartilage)
The transverse arytenoid muscle and the oblique arytenoid muscle ‘adducts’ the vocal folds to close the glottis.
Adversely, the posterior cricoarytenoid muscle ‘abducts’ the vocal folds to open the glottis. The vocal cord cannot open or close by itself.
Additionally, the anterior muscle is the cricothyroid muscle and the lateral muscle is the lateral cricoarytenoid muscle.
When I studied anatomy, I heavily investigated the posterior muscles of the throat. It really was challenging to locate each muscle of the larynx. The oblique arytenoid muscle was the hardest to find. This is because that muscle crossed the transverse arytenoid muscle.
The transverse arytenoid muscle is positioned parallel to the oblique arytenoid muscle.
The cricoid cartilage is then under the transverse arytenoid muscle.
The transverse arytenoid muscle is wide but also thin. The oblique arytenoid muscle has two muscles crossing over each other and is quite thick.
Therefore, the oblique arytenoid muscle is little stronger than the transverse arytenoid muscle.
The posterior cricoarytenoid muscle is a part of the coronoid process of the thyroid cartilage (recognizable by its slightly dented shape) which is located behind the lower portion of the cricoid cartilage.The posterior cricoarytenoid muscles are the only laryngeal muscles to open the true vocal cords, allowing inspiration and expiration. The arytenoid cartilage is located on the cricothyroid articulation.
The cricoarytenoid articulation is a saddle joint. This saddle joint connects the arytenoid cartilage to the cricoid cartilage. The arytenoid cartilage rotates with the sliding action of the cricoid cartilage, which needs to be strong to move.
The posterior cricoarytenoid muscle is the only muscle to be able to abduct the vocal fold to open the glottis.