During anaphase, fibres pull the chromosomes towards structures on opposite sides of the cell. What are these structures called?

The structures are called the poles.

Explanation: Anaphase is a stage of mitotic division in which the spindles pull the chromosomes apart into two genetically identical groups. The two genetically identical groups of chromosomes are pulled to the opposite poles of the spindle.

Mitosis is a type of cell division in which a cell divides to produce two identical daughter cells resulting in cells having the same number of chromosomes as the parent cell. Mitosis occurs in body cells or somatic cells and results in cells with diploid number of chromosomes.