A sperm cell (spermatozoon, pl. spermatozoa) is a flagellated cell that serves as the male gamete in fertilisation. Spermatozoa are produced in large quantities by males in the seminiferous tubules of the testes, and are stored in the epididymis. Their part in human reproduction is amongst the most amazing feats of nature due to the intense and exhausting journey sperm make in travelling up the cervix, uterus and (in some cases) fallopian tubes, in order to reach the ovum and fertilise it. They are guided to it partly by a hormone released by the ovum itself.