Effects of ageing on the insertion zones of the human vocal fold

The vocal ligaments insert at the anterior and posterior commissures of the larynx. These structures fulfil biomechanical functions, balancing the dif ferent elastic moduli of tendon, cartilage or bone and undergo age-related changes that may be responsible for voice changes with increasing age. The aim of this study was to analyse the insertion structures of the vocal liga ments by means of macroscopic, histological, immunohistochemical and electr on-microscopic methods and to draw conclusions from age-related structural changes on a functional basis. Investigations were carried out on the laryn ges of 22 males and 15 females (aged 1-95 y). In adolescence, the insertion zone of the vocal ligament tendon, a dense network of connective tissue ri ch in sulphated glycosaminoglycans at the thyroid cartilage, is characteris ed by a layer between tendon and cartilage comparable to fibrocartilage. Th e insertion zone lacks a perichondrium. Collagen fibrils of the vocal ligam ent tendon penetrate directly into the thyroid cartilage. In the insertion area, the chondrocytes are surrounded by collagen fibrils, which show posit ive reactivity to antibodies against type I and type III collagen. Sulphate d glycosaminoglycans are integrated between the collagen fibrils. In the ar ea of the posterior glottis, elastic cartilage rests like a cap on the hyal ine base of the arytenoid cartilage. There is no distinctive border between the structures. With increasing age, ossification of the laryngeal skeleto n occurs, involving hyaline cartilage at the posterior glottis and hyaline and fibrocartilage at the anterior commissure. At the same time, a loss of sulphated glycosaminoglycans is observed inside the vocal ligament tendon. Advanced ossification of the laryngeal skeleton, particularly in the area o f the commissures, an increasing loss of glycosaminoglycans in the vocal li gament tendon and changes in the elastic tissue reduce the elastic modulus between tendon, cartilage and bone, thus 'stiffening' the insertion zones, which could be one factor among others favouring voice changes with advanci ng age.