The seminal vesicles are two lobulated organs about 2 in. (5 cm) long lying on the posterior surface of the bladder.
On the medial side of each vesicle lies the terminal part of the vas deferens. Posteriorly, the seminal vesicles are related to the rectum. Inferiorly, each seminal vesicle narrows and joins the vas deferens of the same side to form the ejaculatory duct.
Each seminal vesicle consists of a much-coiled tube embedded in connective tissue. The function of the seminal vesicles is to produce a secretion that is added to the seminal fluid. The secretions nourish the spermatozoa. During ejaculation, the seminal vesicles contract and expel their contents into the ejaculatory ducts, thus washing the spermatozoa out of the urethra.