Schematic diagram of dynamic changes in the morphology of a salivary epithelial bud as a result of multiple physical and signaling interactions. They include outward and inward forces generated by epithelial proliferation and ECM-mediated effects, respectively, regulation by growth factors, extracellular matrix (ECM), and enzymes that cleave ECM molecules. Boxed region shows part of an E13 SMG with a developing cleft. Red shading denotes ECM molecules. Dotted and solid blue lines denote E-cadherin. Solid black arrows denote direction of action. Solid thin red arrows denote generation of cleavage fragments. Dotted black arrows denote the dynamic and rapid motility of cells within the epithelium. Note that the mesenchymal cells are not shown here, but they surround the salivary epithelium in vivo.