Background: Spread of cancer at the ventral vocal fold insertion zone has been discussed controversially until today. One reason for this is the so far insufficient knowledge of the anatomical structure and function of the insertion zone.
Methods: The present study analyses the structures of laryngeal anterior commissure by means of histological, immunohistochemical and electron microscopical methods. Investigations are performed on vocal cords of 17 male and 13 female (aged 21-88 years) in three planes.
Results: The vocal ligament inserts at the anterior commissure via two characteristic structures: the noduli elastici, which consist of two different morphological zones, and the vocal ligament tendon, a dense mesh of connective tissue rich in sulfated glycosaminoglycans. In the lower part of noduli elastici collagen and elastic fibres form a meshwork around embedded cells; in the upper part fibres are running in parallel. The vocal ligament tendon is connected to the thyroidal cartilage or bone by fibrocartilage. This area lacks a perichondrium or periosteum. At the beginning of osteogenesis vessels of plica vocals penetrate the bony thyroidal skeleton and contact with extralaryngeal vessels.
Conclusions: Connective tissue cells of the insertion zone and extracellular matrix components formed by these cells fulfil biomechanical functions by equalizing the different elastic moduli of tendon, cartilage or bone. Ventral spread of vocal fold carcinomas is made possible by the lack of periosteum in the insertion zone as well as ossification and associated vascularisation of the thyroid cartilage.