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Tubular structure enclosed by a membrane found within animal and plant cells. Of varying length, they have several functions. They help give shape to many cells and are major components of cilia and flagella, participate in the formation of the spindle during cell division (mitosis), and assist the movement of vesicles from the cell bodies of nerve cells toward the ends of those cells' long extensions (axons) and back to the cell bodies.
This entry comes from Encyclopædia Britannica Concise. For the full entry on microtubule, visit Britannica.com.