The seminal vesicleis a male-specific structure which is about 2 inches or 5 centimeters long and is located behind the urinary bladder and above the prostate gland. The seminal vesiclesare also...
'Seminal vesicle' means either of a pair of glands located on either side of the male urinary bladder that open into the vas deferens and that secrete many components of semen during ejaculation
The seminal vesicle is a slimy and waterly stuff that goes trough your penis it's function is to secrete a significant proportion of the fluid that ultimately becomes semen.