Histological structure and basic classification
Morphologically, all laryngeal muscles are formed by striated muscle tissue. In exams, students sometimes mistakenly choose options with smooth, cardiac, or mixed musculature, but it is important to remember: the laryngeal musculature is strictly striated.
Topographically and biomechanically, the entire muscular apparatus of the larynx can be divided into two large categories:
- Muscles that move the larynx as a whole (responsible for elevating and lowering the entire organ).
- Intrinsic laryngeal muscles, whose function is to change the position of individual laryngeal cartilages relative to each other.
Functional division of the muscles of the vocal apparatus
The work of the vocal apparatus (glottis) is ensured by intrinsic muscles. According to the direction of their action, they are strictly differentiated into groups. The main reference point for classification is their effect on the rima glottidis and vocal cords (not to be confused with the laryngeal inlet, vestibule, or infraglottic cavity).
Four functional groups are distinguished:
- Constrictors of the rima glottidis.
- Dilators of the rima glottidis.
- Tensors of the vocal cords.
- Relaxers of the vocal cords.
Main laryngeal muscles
Among the most important intrinsic muscles controlling the cartilages and vocal cords, the following are distinguished:
- Posterior cricoarytenoid muscle (m. cricoarytenoideus posterior). This is the most critically important muscle for respiration, as it is the only one that widens the rima glottidis.
- Lateral cricoarytenoid muscle (m. cricoarytenoideus lateralis).
- Transverse arytenoid muscle (m. arytenoideus transversus).
- Vocal muscle (m. vocalis).
- Cricothyroid muscle (m. cricothyroideus). The main function of this muscle is to tense the vocal cords.
Briefly: answers to topical questions
What is the innervation of the laryngeal muscles and by which nerves is it provided?
The innervation of the laryngeal muscles is provided by branches of the vagus nerve — the superior laryngeal and recurrent laryngeal nerves. The external branch of the superior laryngeal nerve innervates the cricothyroid muscle. Motor innervation of the remaining intrinsic laryngeal muscles is carried out by the recurrent laryngeal nerve (or its continuation — the inferior laryngeal nerve), which innervates the laryngeal muscles except for the cricothyroid.
Which laryngeal muscles perform the function of narrowing the rima glottidis?
The cited sources indicate that laryngeal muscles are subdivided by function into constrictors and dilators of the rima glottidis, however, the specific list of muscles narrowing the rima glottidis is not provided.
What is the blood supply to the laryngeal muscles?
The blood supply to the larynx is provided by the superior and inferior laryngeal arteries: the superior laryngeal artery (a. laryngea superior) branches from the superior thyroid artery (a. thyroidea superior), and the inferior laryngeal artery (a. laryngea inferior) branches from the inferior thyroid artery (a. thyroidea inferior).
To avoid confusion regarding their functions, remember: "Posterior means open." The posterior cricoarytenoid muscle (m. cricoarytenoideus posterior) is the only dilator that widens the rima glottidis.
Class and exam questions
What type of muscle tissue forms the laryngeal muscles?
All laryngeal muscles are exclusively striated skeletal muscle. There are no smooth or mixed fibers in them.
Which laryngeal muscle is responsible for widening the rima glottidis?
This function is performed by only one muscle — the posterior cricoarytenoid muscle (m. cricoarytenoideus posterior).
What does the cricothyroid muscle (m. cricothyroideus) do?
The cricothyroid muscle belongs to the group of muscles that tense the vocal cords.
Into which groups are the laryngeal muscles divided according to their local action?
They are divided into muscles that move the larynx as a whole and intrinsic muscles that change the position of individual cartilages.
What else to study on this topic
- Anatomy of the muscles moving the larynx as a whole.
- The mechanism of action of the lateral cricoarytenoid muscle.
- The role of the transverse arytenoid muscle in narrowing the rima glottidis.
- Structural features and functions of the vocal muscle (m. vocalis).
- The process of vocal cord relaxation and the muscles participating in it.
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