Fig. 3. Retraction fibres provide resistive forces to orient the mitotic spindle. (A) Interphase cell, showing sites of attachment to the ECM via integrin adhesions and the intracellular cytoskeleton. This is the view that is seen when looking down on cells in 2D culture. (B) Mitotic cell that has rounded up in preparation for cytokinesis. The cell remains attached to the substratum through retraction fibres, which provide resistance so that tension can build up within microtubules and thereby orient the spindle.