Fig. 2. A model for the steps of cell migration. A migrating cell extends a lamellipodium at the front. This extension is stabilized through the formation of new adhesions to the extracellular matrix. The cell body is moved forward by actomyosin-mediated contraction. Finally, the tail of the cell detaches from the substratum and retracts. Migrating cells also secrete proteases that cut up extracellular matrix proteins, and this is important for cell movement.