Ejaculation is the process of ejecting semen from the penis, and is usually accompanied by an orgasm as a result of sexual excitement. If it occurs spontaneously during sleep it is commonly called a wet dream. This can be brought on by a particularly vivid and exciting sexual dream.
Precum is a lubricating, clear, sticky fluid that flows out of the urethra of most men when they are sexually excited. Most guys first notice this as an embarrassing wet spot on their pants. It prepares the urethra for semen by neutralizing any traces of urine in the urethra so that the sperm are not damaged on their way out. The other thing it does is to lubricate the movement of the foreskin over the glans - if you have a foreskin. This is the base fluid for sperm, which need something to carry them and to buffer the vagina's pH to a suitable value that will let them survive long enough to travel into the uterus and up to the Fallopian Tubes. Precum semen fluid can contain small amounts of sperm. There seems to be some dispute about whether the pre-cum sperm can cause pregnancy but caution is wise if you are also involved with girls. The amount of precum fluid various greatly from man to man and all amounts of precum are normal.
Ejaculation is a reflex which usually cannot be stopped once it has started, at least not without painful cramping. It takes place in two stages 1) emission and 2) ejaculation. During emission, smooth muscles contract and propel mature sperm from the end portions of the epididymis -where it was stored- through a long tube (vas deferens ) inside the body, just beneath the bladder. The beginning of emission is typically experienced as a "point of no return" because at this point the brain receives a signal that ejaculation is about to happen and that nothing can stop the orgasm.
From there, the sperm get mixed with nutrient-rich fluids from the seminal vesicles and a milky secretion from the prostate gland. This combination of sperm and fluids is called semen. During ejaculation, the semen is ejected through the urethra with rhythmical contractions.
The semen does three things:
* Provides a watery environment in which the sperm cells can swim while outside the body * Provides nutrients for the sperm cells (fructose, amino acids, vitamin C) * Protects the sperm cells by neutralizing acids in the female's sexual tract
The force and amount of semen vary widely from male to male. A normal ejaculation may contain anywhere from 2 to 15 mL -from half a teaspoon to a tablespoon- although 5 to 7 mL is typical. This amount is highly dependent on how recent the last previous ejaculation was. In other words, an ejaculation soon after a previous ejaculation will be very small, but will be much larger if ejaculation has not occurred for two days or longer.
In most men, the more semen ejaculated the more pleasurable an orgasm they experience. Some men may be able to shoot their ejaculate a distance of half a metre, while for others, the semen may simply ooze out of the penis. Both situations are normal.