The prostate is a gland situated at the base of the bladder and also at the base of the penis. The seminal vesicles are attached to the prostate, one on each side. The vas deferens joins the testicle and epididymis at one end to the seminal vesicles at the other and it is within the seminal vesicles that the sperms are stored before ejaculation.
The prostate, together with the seminal vesicles, manufactures the seminal fluid. This is a slightly alkaline gelatinous fluid in which sperms can survive indefinitely. The prostate also produces a secretion which may be extruded from the urethra at the end of the penis as a result of sexual excitement or in the early stages of intercourse. This prostatic secretion may occasionally contain sperms and this is why coitus interruptus, or withdrawal, is an inefficient method of contraception.