The seminal vesicles appear as two elongated sacs on the posterior surface of the bladder, separated from each other by the ampullae of the vas deferens. Each seminal vesicle consists of a long, coiled tube, surrounded by smooth muscle. Its duct joins the vas deferens to form the (common) ejaculatory duct. The ejaculatory duct penetrates the posterior wall of the prostate gland, to open into the prostatic urethra. From here, spermatozoa follow the same path as urine that enters the prostatic urethra (i.e., passes through the membranous and penile urethra to be ejected at the tip of the penis).