The correct answer to fill in the blank is:
“Ejaculatory duct”
The ejaculatory duct is about two cm in length and is formed when the seminal vesicle's duct merges with the vas deferens. At this point, the ducts travel through the prostate and drain into the colliculus seminalis's urethra. Essentially, the ejaculatory duct is where the semen is ejaculated.