The penis plays an important role in sex, but its day job is liquid waste management – 800-2000 mL of urine leaves the body through the penis daily, while one ejaculate contains a scant 2-5 mL. More fascinating facts about semen: did you know the seminal vesicles – those rabbit ears atop the prostate – contribute the most liquid by volume to semen? Now ya know about stuff that comes out of your penis.