Microtubule

Self-assembling components of the cytoskeleton. Microtubules are cylindrical protein polymers, interconnected by cross-bridging proteins, which structurally and dynamically organize functional activities in living cells. They form the spindle during mitosis.

An elongated, hollow tubular structure present in the cell. Microtubules help certain cells maintain their rigidity, convert chemical energy into work, and provide a means of transportation of substances in different directions within a cell.