Final answer:
The outer microtubules in a cilium or flagellum are produced from the centrosome, the microtubule-organizing center of eukaryotic cells. Centrioles, within the centrosome, play a key role in the formation of cilia and flagella and their structural maintenance.
Step-by-step explanation:
The outer microtubules in a cilium or a flagellum are generated directly from microtubules in a centrosome. In eukaryotic cells, the centrosome functions as the microtubule-organizing center and is located near the nucleus of animal cells. Each centrosome contains a pair of centrioles, which are involved in the formation of cilia and flagella through their structural similarity to basal bodies. These microtubules are organized in cilia and flagella as a typical 9+2 arrangement, which refers to nine outer doublet microtubules arranged around two central singlet microtubules.
A basal body is involved in the formation of cilia and flagella, and it is structurally similar to a centriole, consisting of nine microtubule triplets. Microtubules grow out from the centrioles by adding more tubulin subunits, which extend outward as cilia or flagella. The productive collaboration between centrosomes, centrioles, microtubules, and motor proteins allows for ciliary and flagellar motion, essential for cell locomotion and the transportation of fluids along the cell surface.