The Scientist: Leah S. Millheiser, M.D., clinical assistant professor of obstetrics and gynecology at Stanford University Medical Center

The Answer: Female ejaculation, aka squirting, is a source of wonder, confusion, occasional distress and a lot of questions for women and men alike. Squirting doesn’t seem to serve a particular biological function, and though it’s perfectly normal and healthy, it’s not especially common, and it is unclear why some women squirt occasionally, some women squirt every time they’re aroused, and many women never experience it at all.

For those who aren’t sure what female ejaculation actually is—and this will likely include women from all three categories above—it’s a large gush of fluid from the vagina during sexual activity. The fluid is watery and copious, and when it rushes out, many women worry that they’ve peed themselves. Rest assured, it’s not urine. However, it does have some of the same components, such as urea. That’s because, the theory goes, the fluid is produced by glandular tissue surrounding the urethra at the opening of the vagina called the urethral sponge. It appears to be the female homologue to the male prostate, and even secretes a protein that is specific to the prostate (aptly called prostate specific antigen). It’s likely just an embryological remnant of the prostate and doesn’t really do anything, though it is possible that the ejaculate it produces acts to lubricate the vagina during sex.

However, it is different from the thicker, viscous lubricant that is typically secreted during arousal, which consists of transudate, a fluid that is pushed out of capillaries in the vaginal wall, mixed with cells shed from the vaginal lining. Ejaculate is a lot thinner, and there’s a lot more of it. It doesn’t always squirt. It is often released in a short burst during arousal, though if secretion takes place in time with orgasm, it’s possible that contractions of the vaginal muscles will provide the propulsion required for a more theatrical ejection.The frequency, timing and volume of ejaculation vary—once or always, at the start of arousal or at orgasm, a little or enough to warrant plastic sheets. But in every case it’s a sign of the same thing: a positive sexual experience.

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