Topography and General Characteristics
The larynx projects onto the anterior neck region. Anteriorly, it is partially covered by the infrahyoid muscles. Laterally and anteriorly, it is closely related to the thyroid gland, while posteriorly it borders the laryngopharynx.
A crucial anatomical feature is the connection of the larynx to the hyoid bone via the thyrohyoid membrane (membrana thyrohyoidea). This robust connection grants the organ high mobility, allowing it to move upward and downward during swallowing or speech.
The dimensions of the larynx vary by sex and age. As a rule, the male larynx is significantly larger than the female larynx, with these anatomical differences becoming particularly pronounced during puberty.
Unpaired Laryngeal Cartilages
The rigid skeletal framework is cartilaginous, featuring three large unpaired cartilages:
- Thyroid cartilage (cartilago thyroidea). This is the largest element, located above the arch of the cricoid cartilage. It consists of right and left laminae (lamina dextra et sinistra), which fuse anteriorly at an angle pointing posteriorly, forming the laryngeal prominence (prominentia laryngea). Superior and inferior thyroid notches (incisura thyroidea superior et inferior) are present on its borders. The posterior borders of the laminae extend into superior and inferior horns (cornua superiora et inferiora). An oblique line (linea obliqua) is visible on the external surface of each lamina for muscle attachments.
- Cricoid cartilage (cartilago cricoidea). Shaped like a signet ring, its expanded posterior portion is the lamina (lamina cartilaginis cricoideae), and its narrower anterior portion is the arch (arcus cartilaginis cricoideae). The superior border of the lamina bears articular surfaces (facies articulares arytenoideae) for articulation with the arytenoid cartilages.
- Epiglottis (cartilago epiglottica). A leaf-shaped elastic cartilage located posterior and slightly superior to the thyroid cartilage, directly behind the root of the tongue. Its narrowed inferior part is the stalk (petiolus epiglottidis), above which projects the epiglottic tubercle (tuberculum epiglotticum). The posterior surface contains small pits housing mucous glands.
Paired Laryngeal Cartilages
The paired elements are smaller structures playing a key role in tensioning the vocal cords:
- Arytenoid cartilage (cartilago arytenoidea). Pyramidal in shape, featuring a broad base (basis cartilaginis arytenoideae) and a superior apex (apex cartilaginis arytenoideae). Two vital processes project from the base: the muscular process (processus muscularis) and the vocal process (processus vocalis). The vocal process serves as the attachment point for the vocal cord.
- Corniculate cartilages (cartilagines corniculatae). Small, often inconstant nodules perched atop the apices of the arytenoid cartilages.
- Cuneiform cartilages (cartilagines cuneiformes). Small nodular cartilages embedded within the aryepiglottic folds of the mucous membrane.
Histology: Most laryngeal cartilages are composed of hyaline cartilage, which tends to ossify with age. However, the epiglottis, corniculate cartilages, cuneiform cartilages, and vocal processes of the arytenoid cartilages consist of elastic cartilage and do not undergo calcification.
Joints, Ligaments, and Membranes
The cartilaginous framework is united by a complex system of joints and ligaments.
The primary suspensory apparatus is the thyrohyoid membrane (membrana thyrohyoidea). Along the midline, it thickens to form the median thyrohyoid ligament (lig. thyrohyoideum medianum), and laterally it forms the lateral thyrohyoid ligaments (ligg. thyrohyoidea lateralia). A small triticeal cartilage (cartilago triticea) is occasionally found embedded within the lateral ligament.
Two paired joints facilitate laryngeal movements:
- Cricothyroid joint (articulatio cricothyroidea).
- Cricoarytenoid joint (articulatio cricoarytenoidea). Rotation of the arytenoid cartilages in this joint causes the vocal folds to approximate or diverge.
Internally, the larynx contains the fibro-elastic membrane of the larynx (membrana fibroelastica laryngis). Its upper part is the quadrangular membrane (membrana quadrangularis), and its lower part is the elastic cone (conus elasticus).
Key internal ligaments include the vestibular ligaments (ligg. vestibulares) and the vocal ligaments (ligg. vocalia). The latter extend between the inner surface of the thyroid cartilage anteriorly and the vocal processes of the arytenoid cartilages posteriorly. The space between them forms the rima glottidis (rima glottidis).