Larynx

The larynx performs respiratory and voice-forming functions, protects the lower respiratory tract from foreign particles. The larynx resembles an irregularly shaped tube, widened at the top and narrowed at the bottom. The upper border of the larynx is at the level of the lower edge of the IV cervical vertebra; the lower - at the lower edge of the VI cervical vertebra. The larynx is located in the anterior region of the neck, its relationship with neighboring organs is complex. At the top, the larynx is attached to the hyoid bone, below - it continues into the trachea. In front, the larynx is covered by the superficial and pretracheal plates of the cervical fascia and the infrahyoid muscles of the neck. In front and on the sides, the larynx is surrounded by the right and left lobes of the thyroid gland. Behind the larynx is the laryngeal part of the pharynx. The close connection of the larynx with the pharynx is explained by the development of the respiratory system (epithelium and glands) from the central wall of the pharyngeal part of the primary intestine and the belonging of the pharynx to both the respiratory and digestive tracts. At the level of the oropharynx, the respiratory and digestive tracts cross.

Sections of the larynx. The larynx is divided into the vestibule, interventricular section and subglottic cavity.

The vestibule of the larynx (vestibulum laryngis) is located between the entrance to the larynx at the top and the vestibular folds (false vocal folds) at the bottom. Between the vestibular folds (plicae vestibulares) is the vestibular fissure (rima vestibuli). The anterior wall of the vestibule (4 cm high) is formed by the epiglottis covered with mucous membrane, and behind it by the arytenoid cartilages. The height of this posterior wall of the vestibule of the larynx is 1.0-1.5 cm. The lateral walls of the vestibule are formed on each side by the aryepiglottic ligament.

The interventricular region, the shortest, is located between the folds of the vestibule above and the vocal folds below.

On each side there is a depression - the ventricle of the larynx (ventriculum laryngis). The right and left vocal folds (plicae vocales) limit the glottis (rima glottidis). The length of this slit in men is 20-24 mm, in women - 16-19 mm. The width of the glottis during breathing is on average 5 mm, and increases during voice production. The larger anterior part of the glottis is called the intermembranous part (pars intermembranacea).

The subglottic cavity (cavitas infraglottica) is the lower part of the larynx, located between the vocal folds at the top and to the entrance to the trachea at the bottom.

Laryngeal cartilages. The basis of the larynx (skeleton) is made up of cartilages connected by ligaments, joints and muscles. Laryngeal cartilages are divided into paired and unpaired. Unpaired cartilages include the thyroid, cricoid cartilages and the epiglottis. Paired cartilages include the arytenoid, corniculate, cuneiform and inconstant granular cartilages of the larynx.

The thyroid cartilage (cartilago thyroidea), the largest cartilage of the larynx, consists of two quadrangular plates connected at an angle in the anterior part of the larynx. The angle of connection of the plates in women is approximately 120°, in men - 90°. In men, this angle protrudes strongly forward, forming the prominence of the larynx (prominentia laryngis) - the "Adam's apple". The right and left plates of the thyroid cartilage (lamina dextra et lamina sinistra) diverge backward and laterally, forming a shield-shaped structure. On the upper edge of the cartilage (above the prominence of the larynx) there is a deep triangular-shaped superior thyroid notch (incisura thyroidea superior). The lower thyroid notch (incisura thyroidea inferior) is weakly expressed, it is located on the lower edge of the cartilage. The posterior edges of the plates on each side form a longer upper horn (cornu superius) and a short lower horn (cornu inferius), which has an articular surface for connection with the cricoid cartilage. On the outer surface of both plates of the thyroid cartilage there is an oblique line (linea obliqua) - the place of attachment of the sternothyroid and thyrohyoid muscles.

The cricoid cartilage (cartilago cricoidea) resembles a ring in shape. It has an anteriorly facing arch (arcus cartilaginis cricoideae) and a posteriorly facing quadrangular wide plate (lamina cartilaginis cricoideae). On the upper lateral edge of the cricoid plate on each side there is an articular surface for articulation with the arytenoid cartilage of the corresponding side. On the lateral part of the cricoid plate, at the place where it transitions into the arch, there is a paired articular surface for connection with the lower horn of the thyroid cartilage.

The arytenoid cartilage (cartilago arytenoidea) externally resembles a pyramid with a downward-facing base and an upward-facing apex. The base of the arytenoid cartilage (basis cartilaginis arytenoideae) has an articular surface (facies articularis), which participates in the formation of the cricoarytenoid joint. The apex of the arytenoid cartilage (apex cartilaginis arytenoideae) is pointed and inclined backwards. Anterior to the base of the arytenoid cartilage is a short vocal process (processus vocalis), formed by elastic cartilage. The vocal cord is attached to this process. Laterally from the base of the arytenoid cartilage is a short and thick muscular process (processus muscularis), to which the muscles that set the arytenoid cartilage in motion are attached. The arytenoid cartilage has an anterolateral surface with a small oblong fossa, medial and posterior surfaces. In the lower part of the anterolateral surface there is a small oblong fossa (fovea oblongata). The medial surface faces the same surface of the arytenoid cartilage on the opposite side. The transverse and oblique arytenoid muscles are adjacent to the concave posterior surface.

The epiglottis (epiglottis) is leaf-shaped, flexible, resilient, and elastic. The epiglottis has a narrow lower part - the petiolus (petiolus epiglottidis) and a wide rounded upper part. The petiolus of the epiglottis is attached to the inner surface of the thyroid cartilage, below its superior notch. The epiglottis is located above the entrance to the larynx, covering it from the front and from above. The anterior surface of the epiglottis is convex, facing the root of the tongue and the body of the hyoid bone. The concave posterior surface of the epiglottis is directed toward the vestibule of the larynx. On this surface, numerous pits are visible - the mouths of the mucous glands, and an elevation - the epiglottal tubercle (tuberculum epiglotticum).

The corniculate cartilage, Santorini's cartilage (cartilago corniculata), is elastic, located on the top of the arytenoid cartilage, and forms a protruding corniculate tubercle (tuberculum corniculatum).

The sphenoid cartilage, or Wrysberg's cartilage (cartilago cuneiformis), is small in size and is located in the thickness of the aryepiglottic fold, above and in front of the corniculate cartilage. The sphenoid cartilage forms the wedge-shaped tubercle (tuberculum cuneiforme), which forms an elevation (thickening) near this ligament.

The granular cartilage (cartilago triticea) is paired, variable, small in size, and located in the thickness of the lateral thyrohyoid ligament, stretched between the superior horn of the thyroid cartilage and the end of the greater horn of the hyoid bone.

Joints and ligaments of the larynx. The cartilages of the larynx are mobile, which is ensured by the presence of two pairs of joints and the muscles acting on them.

The cricothyroid joint (articulatio cricothyroidea) is paired and formed by the articulation of the articular surface of the inferior horn of the thyroid cartilage and the articular surface on the lateral surface of the plate of the cricoid cartilage. This joint is combined, movements are performed simultaneously in both joints relative to the frontal axis. The thyroid cartilage, when the corresponding muscles contract, tilts forward and returns to its original position. When the thyroid cartilage tilts forward, the distance between its angle and the base of the arytenoid cartilage increases. The corresponding vocal cord is stretched.

The cricoarytenoid joint (articulatio cricoarytenoidea) is paired and formed by the articular surfaces of the base of the arytenoid cartilage and the superolateral edge of the cricoid cartilage plate. In the cricoarytenoid joints, movements occur around the vertical axis. When the arytenoid cartilages rotate inward, their vocal processes come closer together and the glottis narrows. When the arytenoid cartilages rotate outward, the vocal processes diverge to the sides and the glottis widens. Slight sliding of the arytenoid cartilages relative to the cricoid cartilage plate is possible. When the arytenoid cartilages come closer together, the posterior part of the glottis narrows; when the cartilages move away from each other, it widens.

In addition to the joints, the cartilages of the larynx are connected to each other, as well as to the hyoid bone, by numerous ligaments.

The thyrohyoid membrane (membrana thyrohyoidea) suspends the larynx from the hyoid bone. This membrane is attached below to the upper edge of the thyroid cartilage and above to the hyoid bone. The thyrohyoid membrane thickens in its middle part and forms the median thyrohyoid ligament (lig.thyrohyoideum medianum). The lateral parts of the thyrohyoid membrane also form thickenings: the right and left lateral thyrohyoid ligaments (lig.thyrohyoideum laterale). The anterior surface of the epiglottis is attached to the hyoid bone by the hyoepiglottic ligament (lig.hyoepiglotticum) and to the thyroid cartilage by the thyroepiglottic ligament (lig.thyroepiglotticum). The median cricothyroid ligament (lig.cricothyroideum medianum) begins at the upper edge of the cricoid arch and attaches to the lower edge of the thyroid cartilage. It prevents the thyroid cartilage from falling backwards. The cricotracheal ligament (lig.cricotracheale) connects the lower edge of the cricoid arch with the upper edge of the first tracheal cartilage.

The walls of the larynx are formed by three membranes: mucous, fibrocartilaginous and adventitia. The mucous membrane is lined mainly with multi-row ciliated epithelium. Only the vocal folds are covered with flat multi-layered epithelium. The proper plate of the mucous membrane, represented by loose fibrous connective tissue, contains a significant number of elastic fibers that do not have a specific orientation. Elastic fibers penetrate the perichondrium. In the thickness of the proper plate of the mucous membrane there are numerous protein-mucous glands. They are especially numerous in the area of the folds of the vestibule and in the folds of the ventricles of the larynx. There are no glands in the area of the vocal cords. In the thickness of the proper plate of the mucous membrane there is a significant amount of lymphoid tissue. Especially large accumulations of it are located in the walls of the ventricles of the larynx. The muscular plate of the mucous membrane of the larynx is almost not developed. The submucosa of the larynx is compacted due to the significant content of fibrous and elastic fibers, which form a fairly dense fibrous-elastic membrane. The fibrous-elastic membrane (membrana fibroelastica) is divided into two parts: the quadrangular membrane and the elastic cone.

The quadrangular membrane (membrana quadrangulitis) corresponds to the vestibule of the larynx. Its upper edge reaches the arytenoid folds on each side. The lower free edge is located on each side in the thickness of the folds of the vestibule of the larynx. The elastic cone (conus elasticus) corresponds to the location of the subglottic cavity. The upper free edge of the elastic cone is thickened, stretched between the angle of the thyroid cartilage in front and the vocal processes of the arytenoid cartilages behind, forming the vocal cords (plicae vocales). The lower edge of the elastic cone is attached to the upper edge of the arch and to the anterior edges of the plate of the cricoid cartilage.

The fibrocartilaginous membrane of the larynx is represented by hyaline and elastic cartilages. Elastic cartilage forms the epiglottis, sphenoid and corniculate cartilages, and the vocal process of the arytenoid cartilages. The thyroid, cricoid, and arytenoid cartilages of the larynx are hyaline. The adventitia is formed by loose fibrous connective tissue.

The process of voice formation. The vocal folds (ligaments) of the larynx vibrate and create sound when exhaled air passes through the glottis. The strength and pitch of the sound depend on the speed of air passing through the glottis and on the tension of the vocal cords. Shades of speech are formed when in contact with the lips, tongue, and palate. The cavity of the larynx and paranasal sinuses serve as sound resonators.

Roentgen anatomy of the larynx. The larynx can be examined using radiography in the anterior and lateral projections. The radiograph shows the hyoid bone, shadows of the laryngeal cartilages (thyroid, cricoid, epiglottis), and the glottis.

Innervation: superior and inferior laryngeal nerves (from the vagus nerve), laryngeal-pharyngeal branches (from the sympathetic trunk).

Blood supply: superior laryngeal artery (from the superior thyroid artery), inferior laryngeal artery (from the inferior thyroid artery). Venous drainage: superior and inferior laryngeal veins (tributaries of the internal jugular vein).

Lymph drainage: into the deep lymph nodes of the neck (internal jugular, prelaryngeal nodes).

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