If you know anything about sex and reproduction, you probably know something about semen. Like, it's what comes out of the penis when a guy ejaculates. And without it, no babies would be born.
But what about the details? What exactly is semen, anyway, and what does it have to do with sperm, cum, and pre-cum? Should "normal" semen have a certain look to it? How about smell or taste?
Like a Fish in Water
Sperm (short for "spermatozoa") are male reproductive cells. One sperm (spermatozoan), made in the testicles in a biological process known as spermatogenesis, is one cell.
Human sperm are mobile and eel-like; they swim in liquid using their whip-like tails, which are called flagella. This swimming, of course, is the key to a sperm cell's ability to fertilize. The strongest swimmers have the best chance of reaching an egg. Weak ones languish and die. When a healthy male ejaculates, millions of sperm are propelled out of his penis — 200–300 million on the average.
One sperm — and only one, if an egg gives it the opportunity — fertilizes an egg. This can lead to pregnancy, if the fertilized egg implants in the lining of the uterus and starts releasing the hormones needed to keep a pregnancy going.
Semen
Sperm is produced in the testes, the soft ball-like glands in the scrotum. While sperm is the critical component of the male "load," it doesn't make its journey alone. As sperm is pushed through the male reproductive tract by muscular contractions during ejaculation it mixes with several other fluids. The first is squeezed out of the prostate gland, which is located near the bladder. Its milky white fluid creates a chemical environment to help sperm move when they are in a woman's reproductive tract.
The next fluid is squeezed out of the seminal vesicles that are located further down from the bladder on the urethra. Seminal fluid is a sugar-rich food source for sperm that it can use for energy when it is in a woman's reproductive tract. The muscular contractions of ejaculation mix the sperm, prostatic fluid, and seminal fluid to form semen and then push it out the tip of the penis.
Pre-cum
But before ejaculation, the stage is set by another fluid. Secretions from the Cowper's glands, which are located below the seminal vesicles on the urethra, form pre-ejacualte or pre-cum. It oozes along the urethra to make it slippery enough to speed the semen along the way during ejaculation. It also neutralizes the chemistry of the urethra and vagina to make it more likely for the sperm to survive.
After a guy becomes sexually excited, but before he ejaculates, his penis will typically leak pre-cum. It is usually clear and colorless, can vary in volume, and does not contain sperm. (But it can pick up live sperm up from previous ejaculations in a man's reproductive tract.)
Pregnancy can happen when pre-cum with sperm in it gets in the vagina or on the vulva.
Look, Smell, and Taste
When a guy ejaculates, you can't just look at it and see individual sperm — at least not without a microscope. What you can see is semen. In most cases semen is white to yellowish-gray in color (it's often described as "milky"), and is anywhere from opaque to almost transparent.
Semen can have a salty, bitter, or sweet taste. It may be thick and stringy, gooey and clumpy, or thin and drippy. "Normal" semen, in other words, varies from person to person. The taste even varies depending on an individual's diet, whether he's a smoker, or whether he's taken medications or drugs, including alcohol. So each guy's semen is bound to look, smell, and taste a bit different from everyone else's.
Volume
So how much is normal? The short answer is, "that depends." While an average ejaculation might measure about a teaspoon in volume, you could have one that has more or have one that has less. If a guy just ejaculated a short time ago, chances are his next ejaculation will be smaller. But then again, maybe not. If it's been a long time since he ejaculated last, it might be bigger, but then again, maybe not.
Sometimes guys will ejaculate only a little semen with hundreds of millions of sperm, sometimes they will ejaculate a lot of semen with only a few million sperm. Or vice versa — the volume of ejaculate does not determine sperm count.
The moral of the story? Semen, sperm, ejaculations, and pre-ejaculate come in all shapes and sizes, like snowflakes. Consider yours (or your partner's) unique.
