they cause a hypertrophy of striated muscles with a reduction in the fat cells in skeletal muscles, and a reduction in the whole body fatty mass. Androgens are the most important hormones responsible for the passage of the boy-child voice to man voice, and the change is irreversible. The thyroid prominence appears, the vocal folds lengthen and become rounded, and the epithelium thickens with the formation of three distinct layers in the lamina propria. Adulthood Human vocal cords are paired structures located in the larynx, just above the trachea, which vibrate and are brought in contact during phonation. The human vocal cords are roughly 12 – 24 mm in length, and 3–5 mm thick. Histologically, the human vocal cords are a laminated structure composed of five different layers. The vocalis muscle, main body of the vocal cords, is covered by the mucosa, which consists of the epithelium and the lamina propria. The latter is a pliable layer of connective tissue subdivided into three layers: the superficial layer (SL), the intermediate layer (IL), and the deep layer (DL). Layer distinction is either made looking at differential in cell content or extracellular matrix (extracellular matrix) content. The most common way being to look at the extracellular matrix content. The SLP has fewer elastic and collagenous fibers than the two other layers, and thus is looser and more pliable. The ILP is mostly composed of elastic fibers, while the DLP has fewer elastic fibers, and more collagenous fibers. In those two layers, which form what is known as the vocalis ligament, the elastic and collagenous fibers are densely packed as bundles that run almost parallel to the edge of the vocal fold. There is a steady increase in the elastin content of the lamina propria as humans age (elastin is a yellow scleroprotein, the essential constituent of the elastic connective tissue) resulting in a decrease in the ability of the lamina propria to expand caused by cross-branching of the elastin fibers. Among other things, this leads to the mature voice being better suited to the rigors of opera. The extracellular matrix of the vocal cord LP is composed of fibrous proteins such as collagen and elastin, and interstitial molecules such as HA, a non-sulfated glycosaminoglycan. While the SLP is rather poor in elastic and collagenous fibers, the ILP and DLP are mostly composed of it, with the concentration of elastic fibers decreasing and