what is actually in the vagina that creates lots of ecstasy,moaning and joy for most men when having sex?

during sex,what actually is in the vagina or what causes so much ecstasy whenever men penetrate the vagina?Biologically,what cause this ecstasy when a man penetrates the vagina?Is it just the lubrication?

: http://alcoholdrugstreatment.info/what-is-actually-in-the-vagina-that-creates-lots-of-ecstasymoaning-and-joy-for-most-men-when-having-sex-2