Particular structure of the anterior third of the human true vocal cord

Subglottic region: normal topography and possible clinical implications

A precise definition of clinically important laryngeal regions and compartments is still a matter of controversy. The often neglected subglottic area was reinvestigated in plastinated serial sections of 21 human adult specimens. The superior border of the subglottic region is defined by the transition of squamous stratified epithelium covering the vocal cords into the respiratory epithelium of the caudal airways. It is found at the inferior margin of the vocal fold at variable distance from the free edge of the vocal cord and bears a high risk of carcinogenesis. The anterior border of the subglottic region is the cricothyroid space between the thyroid cartilage and cricoid arch. Medially, it is bridged by the median cricothyroid ligament. Laterally, the gap between thyroid and cricoid cartilage is filled by adipose tissue in most cases. This provides a broad connection of intra- and extralaryngeal connective tissue. There, cancer may escape the larynx. The conus elasticus is often regarded as a firm fibroelastic membrane within the subglottic region, but its structure may be disturbed by piercing blood vessels or age-related changes, facilitating cancerous spread. The cricoid lamina representing the dorsal border of the subglottic space ossifies preferentially in its superior part, which is often attacked by tumor invasion. The inferior border of the subglottic region is defined at the inferior rim of the cricoid cartilage. At this level, the endocricoid submucosal tissue contains loosely arranged collagenous fibers, which probably do not act as an anatomic barrier.

Distribution of immunocompetent cells in various areas in the normal laryngeal mucosa of the rat

The larynx can be divided into a supraglottic, a glottic and a subglottic area, each serving different functions. In many cases of laryngitis the site of infection is located in one area, leaving other areas unaffected. It seems reasonable to speculate that the underlying cause of the heterogeneous infection pattern in the larynx is the different processing of infectious agents. Therefore, the number and distribution of granulocytes, macrophages, dendritic cells, natural killer cells and T and B lymphocytes in the normal laryngeal mucosa of young rats were studied. The results show that, with the exception of granulocytes, all subpopulations were present in different numbers. Many macrophages and dendritic cells but only a few natural killer cells and T and B lymphocytes were located in the mucosa. Dendritic cells, natural killer cells and T and B lymphocytes were rarely present in the vocal fold area, whereas in the subglottic area they were present in high numbers. Thus, differences in the composition of immunocompetent cell populations between laryngeal areas were detectable.

The attachments of the conus elasticus to the laryngeal skeleton: physiologic and clinical implications

The attachments of the inferior and dorsal extensions of the lateral parts of the conus elasticus (CE) are not fully understood. A re-investigation was done in plastinated serial sections of 20 adult human larynges. The CE consists of a coherent sheet of connective tissue fibers dividing into two layers toward the inferior anchorage to the cricoid arch, and the posterior anchorage to the cricoid lamina. Caudally, the medial fiber layer is continuous with the submucous fibroelastic membrane of the trachea and is not connected to the cricoid cartilage. The lateral caudal fiber layer is attached to the superior rim of the cricoid arch. Dorsally, both layers of the CE are fixed to the cricoid lamina, the lateral sheet to the lateral edge of the cartilage, the medial sheet to its anterior perichondrium near the midline. Towards the cricoarytenoid joint, the dorsal extension of the CE divides into a caudal and a cranial sheet including a fold of adipose tissue at the base of the arytenoid cartilage. The cranial layer extends towards the vocal process, the caudal layer radiates into the joint capsule and may therefore influence the complicated joint mechanics. The firm attachments of the CE to the cricoid cartilage probably counteract deformations of the CE during phonation. An insufficient fixation of the CE may contribute to an obstruction of the airways causing sleep apnea.