PATHOLOGY

Detailed explanation-1: -Plant cells do not have the centrosomes, which initiate cell division in animal cells. Therefore, spindle fibre formation is brought about by microtubules or cytoplasmic strands.

Detailed explanation-2: -The spindle apparatus of a cell is comprised of spindle fibers, motor proteins, chromosomes, and, in some animal cells, microtubule arrays called asters. Spindle fibers are produced in the centrosome from cylindrical microtubules called centrioles.

Detailed explanation-3: -Centrioles are constructed of microtubules. In animal cells centrioles organise the pericentriolar material to produce microtubules including mitotic spindle fibres.

Detailed explanation-4: -The structure involved in the formation of spindle fibres are centrioles. They exist in a pair close to the nucleus and are present only in the animal cell.