The seminal vesicles are a pair of glands on the posterior surface of the Urinary bladder of male. The seminal vesicles are located behind the prostate and the bladder .The two seminal vesicles empty into the Urethra near the Prostate gland along with the vas deferens (they are the tubes coming from the Testes).

They secrete a significant proportion of the fluid that ultimately becomes semen. About 60% of the seminal fluid in humans originates from the seminal vesicles. Their primary purpose is to supply a viscous, alkaline secretion that forms a part of the seminal fluid. Seminal fluid is often referred to as semen and includes secretions from the seminal vesicles, prostate and bulbourethral glands, as well as sperm cells. The seminal vesicles supply about 30% of the seminal fluid volume. Once sperm are produced, they travel through a collection area, called the epididymis. The seminal vesicles produce a fluid that provides nutrients for the sperm and lubricates the Urethra. This fluid mixes with other fluids to create the semen. During ejaculation, muscles surrounding the seminal vesicles contract and push out the sperm and the fluid from the seminal vesicles like. Seminal vesicle secretions contain proteins, enzymes, fructose, phosphorylcholine and prostaglandins.

One drop of seminal fluid contains about four billion sperm cells and only one is needed to fertilize a single egg.