Animal Cell Shape: The Importance of the Cytoskeleton

Animal cells have no cell walls, so their shapes are controlled by a combination of their own cytoskeleton and, unless the cells live in suspension as blood cells do, their attachments to other cells and matrices. Without the cytoskeleton, suspended cells would have shapes dominated by surface tension, as do soap bubbles. With the cytoskeleton they form tensegrity structures, compression being borne by some elements (typically microtubules) and tension by others (typically actin/myosin). The longevity of these cytoskeletal components can be modulated by proteins (e.g. on the inside of cell-cell junctions) and by mechanical force. This produces a feedback effect, stabilizing elements sited so that they can carry/resist mechanical force, and allowing badly placed elements to be recycled. This achieves adaptive self-organization. Alteration of cytoskeletal dynamics is also used to produce cell processes.