The initial pattern of signaling appears to be established by early and more global embryonic patterning systems. The fibroblast growth factor pathway is then modified at each stage of branching by genetic feedback controls and other signals to give distinct branching outcomes. The reiterative use of a fibroblast growth factor signaling pathway by both insects and mammals suggests a general scheme for patterning branch morphogenesis. Genetic control of branching morphogenesis. The human trachea, for example, is a single tube that runs through the throat, then divides to form the bronchi, which in turn divide to form the airway passages of the lung.
Growth factors are peptide hormones that regulate the growth of cells and tissues.