how both urine and semen pass through penis??why both don't come out together?or why semen doesnot come out without sexual arousal?when and at what time,age semen is ejaculated from penis?

how both urine and semen pass through penis??why both don't come out t

1.	how both urine and semen pass through penis??why both don't come out together?or why semen doesnot come out without sexual arousal?when and at what time,age semen is ejaculated from penis?
Answer» how both urine and semen pass through penis??why both don't come out together?or why semen doesnot come out without sexual arousal?when and at what time,age semen is ejaculated from penis?