The man’s internal genitalia consist of testicles situated in the scrotum, these produce sperm and the male sex hormone testosterone. A spermatic cord runs from each testicle to the seminal vesicles and the prostate gland. The seminal vesicles and the prostate gland produce most of the fluid in the sperm.
The woman’s internal genitalia consist of the ovaries which produce the egg cells and the female sex hormone oestrogen. Once a month an egg cell is released into one of the Fallopian tubes. A Fallopian tube runs from each of the ovaries to the womb. If the egg cell meets a sperm cell new life starts, and the fertilised egg starts to grow and attaches itself to the lining of the womb. If the egg cell does not meet a sperm cell, it will be flushed out of the vagina along with the period.