The seminal vesicles or seminal glands are two tube-like glands located between the bladder and the rectum, behind the prostate. Each vesicle consists of a 3-5 cm coiled tube containing multiple pouches.
The seminal vesicles contribute between 50-80% of the components found in semen, specifically the late ejaculate fluids that support the successful transfer of sperm out of the body. The fluid produced by the seminal vesicles is alkaline, meaning it has a high pH, which provides protection for the spermatozoa in the acidic environment of the female vagina. Seminal vesicles also contribute fructose to semen, which is used as an energy source by spermatozoa, as well as other proteins and enzymes.
A critical component of semen that is provided by the seminal vesicles is semenogelin. This protein creates a gel-like barrier around ejaculated spermatozoa to ensure that capacitation does not occur prematurely.
Each seminal vesicle combines with the vas deferens at the ejaculatory duct, which carries semen through the prostate and into the urethra prior to exiting the body during ejaculation.