Sperm tails Transmission electron micrograph (TEM) of sperm tails. The ends of the tails are the smallest round structures. The tail's motility is aided by the arrangement of microtubules (part of the cell cytoskeleton) within the tail. The microtubules are arranged in a central axoneme, with a central pair of microtubules surrounded by nine other pairs in a ring. Magnification: x10, 000 when printed 10 centimetres high.