Cricoid Cartilage

CRICOID CARTILAGE (cartilago cricoidea) is the primary cartilage in the skeleton of the larynx; the thyroid cartilage and both arytenoid cartilages are situated upon it (see Vol. VII, p. 771, Figure 1 and p. 774, Figure 4). It has the shape of a signet ring, the anterior part of which is narrow, while the posterior part resembles the seal of a ring and appears as an irregular hexagon with unequal sides and angles. The expansion of the cartilage posteriorly occurs at the expense of its upper edge, while its lower edge lies at the same level as the lower edge of the anterior part of the ring. The anterior narrow part of the cartilage is called the arch (arcus cricoideus), and the posterior wide part is the lamina (lamina cartilaginis cricoideae). On the posterior surface of the ring, facing the lumen of the esophagus, there are two depressions on either side of the midline to which the fibers of the posterior cricoarytenoid muscles, which open the glottis, are attached. On the lateral sides of the cartilage, where the narrow part begins to transition into the wide lamina, there are small tubercles with flattened tops; these are articular surfaces and form true joints with the small inferior horns of the thyroid cartilage. On the upper edge of the cricoid lamina, there are two more articular facets for articulation with the bases of the arytenoid cartilages. All 4 joints are provided with capsular ligaments, which are named according to their places of attachment: lig. thyreo-cricoidea lateralia and lig. crico-arytaenoidea. From the anterior segment of the cricoid cartilage, a wide, gradually narrowing ligament extends upward and attaches to the middle of the lower edge of the thyroid cartilage—lig. thyreo-cricoideum medium, or conicum. The lower edge of the cricoid cartilage is connected to the first ring of the trachea by a fibrous membrane—lig. crico-tracheale. By histological structure, the cricoid cartilage belongs to the hyaline cartilages. Like other cartilages of the larynx, the cricoid cartilage undergoes ossification with age, but here this process occurs significantly later than, for example, in the thyroid cartilage, where lime deposition is noted as early as 18–20 years of age. The duration of the ossification period varies individually; in some people, complete ossification of the entire cartilage is observed by the end of the third decade. The process first involves the upper posterior part of the cartilage, mainly the areas of articulation with the arytenoids and the lower horns of the thyroid cartilage; subsequently, the anterior arch of the cricoid cartilage also becomes calcified. The cause of lime deposition is unknown. The anterior edge of the cricoid cartilage can be felt on the anterior surface of the neck upon palpation. During a tracheotomy in children, it is the most important landmark, as its edge is easily felt by the finger when moving it along the trachea from bottom to top. In emergency cases of tracheotomy, the cricoid cartilage is often incised instead of the tracheal rings (cricotomy). Diseases of the cricoid cartilage are rare compared to other laryngeal cartilages and usually represent perichondritis of tuberculous or syphilitic origin. The clinical picture of a lesion of the cricoid cartilage is expressed by swelling of the mucous membrane in the subglottic space of the larynx, such that it becomes necessary to resort to a tracheotomy. Simultaneously with the disease of this cartilage, both arytenoid cartilages also suffer, which increases the danger of laryngeal edema.

L. Rabotnov.