The seminal vesicles are a pair of glands on the posterior surface of the urinary bladder of males. 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.
Seminal vesicle secretions contain proteins, enzymes, fructose, phosphorylcholine and prostaglandins.
The two seminal vesicles empty into the urethra near the prostate gland along with the vas deferens (the tubes coming from the testes).