Final answer:
Centrioles are composed of nine peripheral fibrils arranged as a quadruple row of microtubules. They are cylinders made up of nine triplets of microtubules, with accessory proteins holding them together. Centrioles play a crucial role in cellular division by organizing the mitotic spindles during mitosis.
Step-by-step explanation:
Centrioles are composed of nine peripheral fibrils arranged as a quadruple row of microtubules. Each centriole is a cylinder made up of nine triplets of microtubules, with accessory proteins holding them together. Centrioles play a crucial role in cellular division by organizing the mitotic spindles that separate chromosomes during mitosis.