The male of the human species has a penis and a pair of testcles in an external sack called a scrottum. Most every person who has seen the male body unclothed is aware of the extermal differences. The man has only one organ he carries internal for sex and that is the prostate gland.

A boy when he is born has a zero sperm count. He has no sperm in his body until he starts puberty and then his testicles produce sperm and his prostate, an internal organ,  produces most of the fluid that will be ejected when he ejaculates. This organ is dormant until puberty but then produces seminal fluid to carry sperm from puberty until he dies. 

The fluid builds up and makes a man uncomfortable as the pressure builds up. Eventually the pressure must be released and if he does not maturbate he will have a nocturnal emmision also known as a wet dream. So this pressure and discomfort is what makes men pursue women for sex.

The Holy Scriptures are clear. If you want to have sex. Find a wife and have sex ONLY with her.