1.3.3 Muscles of the larynx
The main muscles of the larynx are divided into two groups:
I - external muscles that link it with neighbouring anatomical structures and indirectly involved in the process of phonation, they displace the larynx as a whole;
II - the internal ones, directly involved in the functioning of the larynx when singing, they change the location of cartilage in relation to each other.
The main internal laryngeal muscles controlling the process of singing include paired thyrocricoid muscles, entangling appropriate laryngeal cartilages from above; thyroarytenoid muscles, inherent in the vocal folds; intraarytenoid; cricoarytenoid etc. All these cartilages are fastened together adjustably by ligaments.
Children's cartilaginous skeleton of the larynx in its composition differs from that of adults only by greater flexibility and smaller size. The plates of the infantile thyroid cartilage larynx are combined under a wide angle, so it is more rounded than the adult.
Vocal tract muscles are:
1) muscles relaxing the vocal cords:
- Voice muscle which, in addition to a relaxation of the vocal cords, is involved in narrowing of the glottis and is located in the interior of vocal cords, starting from the inner surface of the thyroid cartilage and are attached to the vocal process and the arytenoid cartilage;
- ricoarytenoid muscle, it starts on the inner surface of the thyroid cartilage and attached to the anterolateral surface of the arytenoid cartilage;
2) muscles that strain the vocal cords:
- Cricothyroid muscle that hangs down the thyroid cartilage on its front, separating it from the arytenoid cartilage. It is located on the anterolateral surface of the larynx; starts from the arc of the cricoid cartilage and is attached to the lower edge of the thyroid cartilage;
3) muscles narrowing the glottis:
- Side cricoarytenoid muscle that pulls the arytenoid cartilage aside, bringing together the vocal processes of arytenoid cartilages. The muscle begins on the side of the cricoid cartilage, and is attached to a muscular process of the arytenoid cartilage
- Transverse arytenoid muscle. It brings arytenoid cartilages together, being stretched between their rear surfaces;
4) muscles that extend the glottis:
- Rear cricoarytenoid muscle that rotates the arytenoid cartilage, removing each other voice processes arytenoid cartilage. Start point of the muscle is on the back surface of the cricoid cartilage, and the place of attachment is the muscular process of the arytenoid cartilage.
- Mucous membrane of the larynx that is connected to the cartilage by the fibrous elastic membrane of the larynx. Mucosa (except vocal cords) is honeycombed with a multi-row prismatic ciliated epithelium. Mucosal folds form the couple of folds of upper threshold and a pair of vocal folds. The groove between vocal and vestibular folds is called the laryngeal ventricle, and the space between the vocal folds is called glottis. With the contraction of the larynx, the size of fissure changes, which, in turn, changes the pitch of sound going through the larynx with air. The area of the vocal cords, the back of the epiglottic cartilage and the inner surface of the arytenoid cartilage is honeycombed with a non-squamous stratified epithelium. The mucosa, except the edges of vocal folds, contains a large number of ducts from the laryngeal glands.