The Cowper’s glands, or bulbourethral glands, are two small structures, each about the size of a pea, located one on each side of the urethra just below where the urethra emerges from the prostate gland (see Figure 4.6). Tiny ducts connect both glands directly to the urethra. When a man is sexually aroused, these organs often secrete a slippery, mucuslike substance that appears as a droplet at the tip of the penis. Like the prostate’s secretions, this fluid is alkaline and helps buffer the acidity of the urethra; it is also thought to lubricate the flow of seminal fluid through the urethra. In many men this secretion does not appear until well after the beginning of arousal, often just before orgasm. Other men report that the droplet appears immediately after they get an erection, and still others rarely or never produce these preejaculatory droplets. All these experiences are normal variations of male sexual functioning.
The fluid from the Cowper’s glands should not be confused with semen; however, it does occasionally contain active, healthy sperm. This is one reason among many why the withdrawal method of birth control is not highly effective. (Withdrawal and other methods of birth control are discussed in Chapter 10.)