The seminal vesicles are two small 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, 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 secretions from the seminal vesicles contain sugars, proteins, and other substances that support sperm health and mobility, playing a crucial role in reproduction.