Human Anatomy Part 1 - K. A. Dyubenko, A. K. Kolomiytsev, Yu. B. Chaykovsky 2002

Special Part
Respiratory System, systema respiratorium [respiratory apparatus, apparatus respiratorius] - General Overview
Larynx

The Larynx is located in the anterior region of the neck at the level of the IV-VI cervical vertebrae. Anteriorly, it is adjacent to the Infrahyoid Muscles; laterally, to the Blood Vessels and nerves forming the neurovascular bundle of the neck; posteriorly, to the oral part of the Pharynx; superiorly, to the Hyoid bone, to which the larynx is suspended; and inferiorly, to The Thyroid Gland and the Trachea, into which the larynx directly continues. The larynx serves as The Organ of voice production. It is structured on THE PRINCIPLE OF a movement organ, meaning it comprises a cartilaginous Skeleton, joints connecting the cartilages, ligaments, and muscles that ensure the active mobility of the cartilages.

The cartilages of the larynx, cartilagines laryngis, are represented by three unpaired and three paired cartilages (Fig. 283).

The thyroid Cartilage, cartilago thyroidea, is the largest, unpaired hyaline cartilage consisting of two laminae (right and left), lamina dextra et sinistra, joined anteriorly at an angle. In men, this angle is acute (60–70°), forming the laryngeal prominence, prominentia laryngea. In women and children, this angle is rounded, making the prominence less pronounced. In the middle of the upper and lower borders of the cartilage are the superior and inferior thyroid notches, incisura thyroidea superior et inferior. The thickened posterior margin of each lamina extends superiorly and inferiorly to form the superior and inferior horns, cornu superius et inferius. The latter features an internal articular surface on its inferior aspect for articulation with the cricoid cartilage. On the external surface of each lamina is the oblique line, linea obliqua, which serves as the attachment site for the sternothyroid and thyrohyoid muscles.

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Fig. 283. Cartilages, ligaments, and JOINTS OF THE larynx: A – lateral view; B – anterior view

Fig. 283. Cartilages, ligaments, and joints of the larynx (Continued):

C – posterior view

The cricoid cartilage, cartilago cricoidea, is an unpaired hyaline cartilage shaped like a signet ring, consisting of an arch, arcus cartilaginis cricoideae, and a posterior lamina, lamina cartilaginis cricoideae. On the superior-lateral angles of the lamina are the arytenoid articular surfaces, facies articularis arytenoidea, for articulation with the arytenoid cartilages, while the posterior-lateral surfaces of the arch bear the thyroid articular surfaces, facies articularis thyroidea.

The epiglottis, epiglottis, is an unpaired elastic cartilage shaped like a leaf-like plate. Its anterior surface faces the Base of the Tongue and connects to the hyoid bone, and its margins connect to the arytenoid cartilages. The posterior surface faces the laryngeal inlet. The lower part of the epiglottis narrows into a stalk, petiolus epiglottidis, attached to the internal surface of the upper margin of the thyroid cartilage. At the lower part of the posterior surface, a projection is formed called the epiglottic tubercle, tuberculum epiglotticum.

The arytenoid cartilage, cartilago arytenoidea, is a paired elastic cartilage shaped like a pyramid. Its base, basis cartilaginis arytenoideae, articulates with the lamina of the cricoid cartilage, while its apex, apex cartilaginis arytenoideae, points upward. It presents three surfaces: medial, facies medialis, posterior, facies posterior, and anterolateral, facies anterolateralis. The latter features a colliculus. Extending from it along the entire surface is the arcuate crest, crista arcuata, which divides the surface into two depressions: the upper triangular, fovea triangularis, and the lower oblong, fovea oblonga.

Two processes extend from the base of the cartilage: the lateral muscular process, processus muscularis, and the anterior vocal process, processus vocalis.

The corniculate cartilage, cartilago corniculata, is a paired elastic cartilage located atop the apex of the arytenoid cartilage.

The cuneiform cartilage, cartilago cuneiformis, is a paired cartilage located anterior to the corniculate cartilage within the aryepiglottic fold.

Between the laryngeal cartilages, There are two pairs of joints that provide cartilage mobility and regulate vocal cord tension.

The cricothyroid joint, articulatio cricothyroidea, is situated between the inferior horns of the thyroid cartilage and the thyroid articular surfaces of the cricoid cartilage. It moves around a frontal axis. The thyroid cartilage moves in this joint, changing its position relative to the arytenoid cartilages. Consequently, the vocal fold stretched between these cartilages is either tensed or relaxed.

The cricoarytenoid joint, articulatio cricoarytenoidea, is located between the base of the arytenoid cartilage and the arytenoid articular surface of the cricoid cartilage. It features a vertical axis of movement around which the arytenoid cartilage rotates. This causes the vocal processes of both cartilages to either approximate or move apart. Additionally, sliding Movements of the arytenoid cartilages toward and away from each other are possible.

The corniculate cartilages articulate with the apices of the arytenoid cartilages via synchondrosis.

A number of syndesmoses exist between the laryngeal cartilages, as well as between the larynx and adjacent Organs (see Fig. 283):

1. Thyrohyoid membrane, membrana thyrohyoidea, consisting of the median thyrohyoid ligament, ligamentum thyrohyoideum medianum, which stretches between the body of the hyoid bone and the upper margin of the thyroid cartilage (in the region of the superior thyroid notch), and the paired lateral thyrohyoid ligament, ligamentum thyrohyoideum laterale, running between the greater horn of the hyoid bone and the upper margin of the thyroid cartilage lamina, including the superior horn. A triticate cartilage is embedded within the latter ligament.

2. Hyoepiglottic ligament, ligamentum hyoepiglotticum, located between the body and horns of the hyoid bone and the middle of the anterior surface of the epiglottis.

3. Thyroepiglottic ligament, ligamentum thyroepiglotticum, situated between the thyroid cartilage and the stalk of the epiglottis.

4. Cricothyroid ligament, ligamentum cricothyroideum, located between the arch of the cricoid cartilage and the inferior notch of the thyroid cartilage. It consists of elastic fibers.

5. Cricotracheal ligament, ligamentum cricotracheale, located between the inferior margin of the cricoid arch and the first tracheal ring.

6. Cricoarytenoid ligament, ligamentum cricoarytenoideum, a paired ligament connecting the cricoid and arytenoid cartilages, forming the lateral extension of the cricothyroid ligament.

7. Cricopharyngeal ligament, ligamentum cricopharyngeum, is located between the lamina of the cricoid cartilage and the pharynx.

8. Vocal fold (vocal ligament), ligamentum vocale, is a paired Structure composed of elastic fibers. It connects to the midpoint of the internal surface of the thyroid cartilage. In fact, this ligament forms the upper free margin of the elastic cone (see below).

9. Vestibular ligament, ligamentum vestibulare, is a paired structure located within the thickness of the fold of the same name, positioned above and parallel to the vocal ligament.

The Muscles of the larynx, musculi laryngis (Fig. 284), are divided into three groups:

- constrictors — narrow the rima glottidis or the laryngeal cavity;

- dilators — widen the rima glottidis or the laryngeal cavity;

- muscles that alter the tension of the vocal cords.