duration per day of 2 hours. Similar treatment on adult vocal cords would quickly result in edema, and subsequently aphonia. Schweinfurth and al. presented the hypothesis that high hyaluronic acid content and distribution in newborn vocal cords is directly associated with newborn crying endurance. These differences in newborn vocal fold composition would also be responsible for newborns inability to articulate sounds, besides the fact that their lamina propria is a uniform structure with no vocal ligament. The layered structure necessary for phonation will start to develop during the infancy and until the adolescence. The fibroblasts in the newborn Reinke's space are immature, showing an oval shape, and a large nucleus-cytoplasm ratio. The rough endoplasmic reticulum and Golgi apparatus, as shown by electron micrographs, are not well developed, indicating that the cells are in a resting phase. The collagenous and reticular fibers in the newborn the vocal cords are fewer than in the adult one, adding to the immaturity of the vocal fold tissue. In the infant, many fibrous components were seen to extend from the macula flava towards the Reinke's space. Fibronectin is very abundant in the Reinke's space of newborn and infant. Fibronectin is a glycoprotein that is believed to act as a template for the oriented deposition of the collagen fibers, stabilizing the collagen fibrils. Fibronectin also acts as a skeleton for the elastic tissue formation. Reticular and collagenous fibers were seen to run along the edges of the vocal cords throughout the entire lamina propria. Fibronectin in the Reinke's space appeared to guide those fibers and orient the fibril deposition. The elastic fibers remained sparse and immature during infancy, mostly made of microfibrils. The fibroblasts in the infant Reinke's space were still sparse but spindle-shaped. Their rough endoplasmic reticulum and Golgi apparatus were still not well developed, indicating that despite the change in shape, the fibroblasts still remained mostly in a resting phase. Few newly released materials were seen adjacent to the fibroblasts. The ground substance content in the infant Reinke's space seemed to decrease over time, as the fibrous component content increased, thus slowly changing the vocal fold structure. Children The infant lamina propria is composed of only one layer, as compared to three in the adult, and there is no vocal ligament. The vocal ligament begins to be present in children at about four years of age. Two layers appear in the lamina propria between