Topography and general characteristics
The larynx projects onto the anterior surface of the neck. Anteriorly, it is partially covered by the infrahyoid muscles. Laterally and anteriorly, the thyroid gland is closely adjacent to it, and posteriorly the organ borders the laryngeal part of the pharynx.
The most important feature is the connection of the larynx with the hyoid bone using the thyrohyoid membrane (membrana thyrohyoidea). It is precisely due to this tight connection that the organ possesses high mobility and is capable of moving up and down during swallowing or speaking.
The dimensions of the organ depend on sex and age. As a rule, the male larynx is significantly larger than the female one, and these anatomical differences begin to manifest particularly clearly during puberty.
Unpaired cartilages of the larynx
The rigid skeleton of the organ is represented by cartilaginous tissue. There are three large unpaired cartilages:
- Thyroid cartilage (cartilago thyroidea). This is the largest element, located above the arch of the cricoid cartilage. It consists of the left and right laminae (lamina dextra et sinistra), which converge at an angle open posteriorly. Anteriorly, at the site of their junction, the laryngeal prominence (prominentia laryngea) is formed. The superior and inferior thyroid notches (incisura thyroidea superior et inferior) are distinguished on the cartilage. The posterior edges of the laminae extend, forming the superior and inferior horns (cornua superiora et inferiora). Externally, an oblique line (linea obliqua) is noticeable on the laminae, to which muscles attach.
- Cricoid cartilage (cartilago cricoidea). Resembles a classic signet ring in shape. Its expanded posterior part is called the lamina (lamina cartilaginis cricoideae), and the narrower anterior part is the arch (arcus cartilaginis cricoideae). On the upper edge of the lamina are articular surfaces (facies articulares arytenoideae) for articulation with the arytenoid cartilages.
- Epiglottis (cartilago epiglottica). A leaf-shaped elastic cartilage located behind and slightly above the thyroid cartilage, at the very root of the tongue. Its narrowed lower part is the stalk (petiolus epiglottidis), above which the epiglottic tubercle (tuberculum epiglotticum) rises. On the posterior surface of the cartilage, there are small depressions where mucous glands reside.
Paired cartilages of the larynx
The paired elements include smaller structures that play a key role in the tension of the vocal cords:
- Arytenoid cartilage (cartilago arytenoidea). It has the shape of a triangular pyramid. Its structure distinguishes a wide base (basis cartilaginis arytenoideae) and an apex directed upwards (apex cartilaginis arytenoideae). Two important processes extend from the base: the muscular process (processus muscularis) and the vocal process (processus vocalis). It is the vocal process that serves as the fixation point for the vocal cords.
- Corniculate cartilages (cartilagines corniculatae). Small, often inconstant cartilages located directly on the apices of the arytenoids.
- Cuneiform cartilages (cartilagines cuneiformes). They are also small in size and lie within the thickness of the aryepiglottic folds of the mucous membrane.
Histological structure: The bulk of the laryngeal cartilages is formed by hyaline tissue, which is prone to ossification with age. However, the epiglottis, corniculate, and cuneiform cartilages, as well as the vocal processes of the arytenoid cartilages, consist of elastic cartilage, which does not undergo calcification.
Joints, ligaments, and membranes
The cartilaginous framework is united into a single whole by a complex system of joints and ligaments.
The main suspending apparatus is the thyrohyoid membrane (membrana thyrohyoidea). Along the median line, it thickens, forming the median thyrohyoid ligament (lig. thyrohyoideum medianum), and laterally—the lateral thyrohyoid ligaments (ligg. thyrohyoidea lateralia). Within the thickness of the lateral ligaments, a small triticeal cartilage (cartilago triticea) can sometimes be found.
Movements in the larynx are provided by two paired joints:
- Cricothyroid joint (articulatio cricothyroidea).
- Cricoarytenoid joint (articulatio cricoarytenoidea). The rotation of the arytenoid cartilages in this joint causes the vocal cords to come together or move apart.
Inside the larynx lies the fibroelastic membrane of the larynx (membrana fibroelastica laryngis). Its upper section is called the quadrangular membrane (membrana quadrangularis), and the lower section is the elastic cone (conus elasticus).
The most important internal ligaments are the vestibular ligaments (ligg. vestibulares) and the vocal cords (ligg. vocalia). The latter are stretched 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).
Briefly: answers to topical questions
What processes does the arytenoid cartilage have and what structures attach to them?
The arytenoid cartilage is paired and resembles a triangular pyramid in shape, from the base of which two processes extend.
- Muscular process (processus muscularis) — the structures attaching to it are not specified in the provided materials.
- Vocal process (processus vocalis) — serves as the attachment site for the vocal cords, which are stretched between the vocal processes of the arytenoid cartilages and the inner surface of the thyroid cartilage.
What sections does the fibroelastic membrane of the larynx consist of, and what ligaments form their free edges?
The fibroelastic membrane of the larynx consists of two sections, the free edges of which form the ligaments of the vocal apparatus.
- Quadrangular membrane (membrana quadrangularis) — represents the upper section of the membrane; its lower end forms the vestibular ligaments.
- Elastic cone (conus elasticus) — is the lower section; its upper edge forms the vocal cords.
What movements are possible in the cricothyroid joint and how do they affect the vocal cords?
In the cricothyroid joint (articulatio cricothyroidea), the thyroid cartilage tilts forward and backward. This changes the tension of the vocal cords.
To easily remember the three unpaired cartilages, use a visual image: "A shield (thyroid) covers a signet ring (cricoid), and from above, all this is covered by the epiglottis".
Class and exam questions
What type of cartilaginous tissue is the larynx formed from?
It is mainly hyaline cartilage (it may ossify with age). But the epiglottis, corniculate, cuneiform cartilages, and the vocal processes of the arytenoids consist of elastic cartilage.
Where exactly are the vocal cords attached?
Anteriorly they are fixed to the inner surface of the thyroid cartilage laminae, and posteriorly—to the vocal processes (processus vocalis) of the paired arytenoid cartilages.
Which joint is responsible for narrowing and widening of the rima glottidis?
This function rests upon the cricoarytenoid joint. When the arytenoid cartilages rotate around the vertical axis, their vocal processes approach or move apart, changing the width of the rima glottidis.
What else to study on this topic
- Topography of the larynx: relationships with the thyroid gland and infrahyoid muscles.
- Detailed structure of the arytenoid cartilage: muscular and vocal processes.
- Structure of the fibroelastic membrane of the larynx (elastic cone).
- Mechanics of movements in the cricoarytenoid and cricothyroid joints.
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