Posterior view of the prostate gland, seminal vesicles, ductus deferens and Cowper's glands (also known as the bulbourethral glands). The ductus deferens joins with the seminal vesicles to form the ejaculatory duct. The seminal vesicles act to secrete a thick alkaline fluid that mixes with the sperm as it passes into the ejaculatory ducts and the urethra. The prostate gland secretes a lubricant that helps to prevent infection in the urethra and protects and energizes sperm. The Cowper's gland produces a thick, clear mucus that is released prior to ejaculation to neutralize traces of acidic urine within the urethra.