Also known as Cowper’s glands (named for English anatomist William Cowper), the bulbourethral glands are two small glands in the reproductive system of male humans, and many male mammals, that produce and secrete a pre-ejaculate fluid called Cowper’s fluid, known colloquially as “pre-cum”.
This fluid is secreted during sexual arousal in order to prepare the man’s urethra for the passage of sperm. The urethra has high levels of acidity, so the fluid from the bulbourethral glands help protect the sperm by creating a more neutral environment in the urethra.
Bulbourethral glands are about the size of a pea in human males, and are found at the back and side of the urethra at the base of the penis. They create and secrete about a teaspoon (~4 milliliters) of fluid during sexual arousal.
It was initially believed that this pre-ejaculatory fluid could contain small amounts of sperm, and therefore potentially cause a pregnancy. However, further studies indicated that this is not the case: the sperm source was rather a leak from the testicles into the vas deferens, rather than from the bulbourethral gland itself.
The Bulbourethral glands in males are similar to the Bartholin’s glands in females. These pea-sized glands were named after the physician, mathematician, and theologian Thomas Bartholin, and are located slightly to the back and left and right of the opening of the vagina. They secrete fluid to lubricate the vagina.