In fact, the cell is capable of stacking in a 'rouleaux' formation within capillaries that are no larger in diameter than the diameter of the erythrocyte itself. It is also capable of deformation as it is driven through valves of the heart or encounters turbulence in the chambers and major arteries. The integrity of the cell is maintained throughout its typical lifetime in humans of three months, despite many passes through the circulation. That integrity and the biconcave shape itself are maintained by a complex network of proteins that interact with the cell membrane in a special way. The network that gives the erythrocyte its special flexibility is called the cytoskeleton .
All cells have a cytoskeleton, and share common elements and modes of organization.
Since the cytoskeleton is intimately involved in cell function, including cell-cell interactions, receptor organization, motility, organization of organelles, endocytosis and exocytosis, cell division, etc. The mammalian erythrocyte is probably the easiest of all cells to use as a model for the organization of cytoskeletal proteins, and in fact the first detailed models of cytoskeletal structure were developed for the erythrocyte membrane. Blood is easily obtained from either animals or humans. The red cells are easily separated from other components by washing and centrifugation. The cells themselves are easily taken apart by osmotic shock and the membranes separated, again by washing and centrifugation.