The seminal vesicle is a pair of glands located behind the bladder in males. They produce a fluid that nourishes and helps transport sperm during ejaculation. This fluid makes up a significant portion of semen, which is the substance that carries sperm out of the body. Each seminal vesicle is about 5 to 7 centimeters long and connects to the vas deferens, where sperm is mixed with the seminal fluid. The fluid contains various substances, including fructose, which provides energy for sperm, and prostaglandins, which help in the movement of sperm towards the egg in the female reproductive system.