The structures that move apart during mitosis and create the spindle are the centrioles.

Here's how it works:

1. Centrioles duplicate: Before mitosis begins, the centrioles, which are small, cylindrical structures found near the nucleus, replicate themselves.

2. Migration to poles: During prophase, the duplicated centrioles migrate to opposite poles of the cell.

3. Spindle fiber formation: As the centrioles move apart, they extend microtubule fibers, forming the spindle apparatus.

4. Chromosome attachment: The spindle fibers attach to the chromosomes at their centromeres.

5. Chromosome separation: During anaphase, the spindle fibers shorten, pulling the sister chromatids of each chromosome towards opposite poles.

6. Cell division: The spindle fibers eventually disappear, and the cell divides into two daughter cells, each containing a complete set of chromosomes.

So, the centrioles are key players in creating the spindle apparatus, which is essential for the proper segregation of chromosomes during mitosis.