Structure and Cartilages

The larynx has a skeletal framework made of cartilages. There are three single cartilages, which are the thyroid, cricoid, and epiglottis, and several paired cartilages, including the arytenoid, corniculate, cuneiform, and sometimes the triticeal cartilages. These cartilages are connected to each other by joints, as well as by synchondroses and ligaments.

The thyroid cartilage is the largest cartilage of the larynx. It is formed by two symmetrical plates that meet in the front to create the laryngeal prominence. These plates form the anterior and lateral walls of the larynx. They are separated above and below by notches, and their posterior edges remain apart to allow space for the cricoid cartilage. 

Each plate has surfaces and margins, and the posterior margin forms horn-like projections called superior and inferior cornua. The inferior cornua articulate with the cricoid cartilage. The outer surface has an oblique line for muscle attachment, while the inner surface is smooth.

The cricoid cartilage is shaped like a signet ring, with a narrow front arch and a wide posterior lamina. It forms the base of the laryngeal skeleton. The lamina is much taller than the arch and has surfaces for articulation with the arytenoid cartilages. The cricoid also has articular surfaces for the thyroid cartilage and supports the structure of the larynx.

The epiglottis is a thin, leaf-shaped cartilage that is curved and covered by mucous membrane. It has a stalk called the petiole, which attaches to the thyroid cartilage. Its structure allows it to form the epiglottis at the entrance of the larynx.

The arytenoid cartilages are paired, small, pyramidal structures that sit on the cricoid cartilage. Each has a base for articulation, an apex, and several surfaces. They also have two processes: the vocal process, which connects to the vocal cords, and the muscular process, which is used for muscle attachment.

The corniculate cartilages sit on top of the arytenoids and act as small extensions of them. The cuneiform cartilages are found within the aryepiglottic folds and contribute to the structure of the laryngeal opening. The triticeal cartilages are small and inconsistent structures found in ligaments.

Laryngeal Cavity and Mucous Membrane

The larynx is lined by mucous membrane that is continuous with the pharynx above and the trachea below. This membrane forms folds and structures within the larynx.

The entrance to the larynx is called the laryngeal inlet (aditus laryngis), and it is bounded by the epiglottis, aryepiglottic folds, and arytenoid cartilages. Inside the larynx, the mucous membrane forms the glottis, which includes the vocal folds and the opening between them, called the rima glottidis.

The vocal folds (true vocal cords) contain the vocal ligaments and muscles. Above them are the vestibular folds (false vocal cords), which are less elastic and do not directly produce sound. Between these folds is a space called the laryngeal ventricle.

Below the glottis, the cavity narrows and follows the shape of the elastic cone. The mucous membrane here is smooth and firmly attached.

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