 The first emergence of mesenchyme occurs during gastrulation from the epithelial–mesenchymal transition (EMT) process.This transition occurs through the loss of epithelial cadherin, tight junctions, and adherens junctions on the cell membranes of epithelial cells.The surface molecules undergo endocytosis and the microtubule cytoskeleton loses shape, enabling mesenchyme to migrate along the extracellular matrix (ECM).