Microtubules, the Structural Foundation of Your Cells

Fibroblast cells showing cytoskeleton.

Microtubules are fibrous, hollow rods that function primarily to help support and shape the cell. They also function as routes along which organelles can move throughout the cytoplasm. Microtubules are typically found in all eukaryotic cells and are a component of the cytoskeleton, as well as cilia and flagella. Microtubules are composed of the protein tubulin.

Cell Movement

Microtubules play a huge role in movement within a cell. They form the spindle fibers that manipulate and separate chromosomes during the mitosis phase of the cell cycle. Examples of microtubule fibers that assist in cell division include polar fibers and kinetochore fibers.

Animal Cell Microtubules

Microtubules also form cell structures called centrioles and asters. Both of these structures are found in animal cells, but not plant cells. Centrioles are composed of groupings of microtubules arranged in a 9 + 3 pattern. Asters are star-shaped microtubule structures that form around each pair of centrioles during cell division. Centrioles and asters help to organize the assembly of spindle fibers that move chromosomes during cell division. This ensures that each daughter cell gets the correct number of chromosomes after mitosis or meiosis. Centrioles also compose cilia and flagella, which allow for cell movement, as demonstrated in sperm cells and cells that line the lungs and female reproductive tract.

Cell movement is accomplished by the dis-assembly and re-assembly of actin filaments and microtubules. Actin filaments, or microfilaments, are solid rod fibers which are a component of the cytoskeleton. Motor proteins, such as myosin, move along actin filaments and cause cytoskeleton fibers to slide alongside one another. This action between microtubules and proteins produces cell movement.