HOW EJACULATION OCCURS??
Ejaculation is the process of ejecting semen from the penis, and is usually accompanied by orgasm as a result of sexual stimulation. It may also occur spontaneously during sleep -called a nocturnal emission-, due to stimulating of the prostate or, rarely, due to prostatic disease.
Ejaculation is a reflex which usually cannot be stopped once it has started, without painful cramping. It has two phases: emission and ejaculation proper. During emission, the two ducts known as vas deferens contract to propel sperm from the epididymis -where it was stored- up to the ampulla’s at the top end of the vas deferens. The beginning of emission is typically experienced as a "point of no return".
The sperm then passes through the ejaculatory ducts and is mixed with fluids from the seminal vesicles, the prostate, and the bulb urethral glands to form the semen or ejaculate. During ejaculation proper, the semen is ejected through the urethra with rhythmical contractions.
The force and amount of ejaculate vary widely from male to male. A normal ejaculation may contain anywhere from 2 to 15 cubic centimeters -from half a teaspoon to a tablespoon- although 5 to 7 cm3 is typical. The amount of ejaculate is highly dependent on how recent the last previous ejaculation was within a range of the first two days. 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 several feet, while the semen may simply ooze out of some men's penises.
The number of sperm in an ejaculation also varies widely, depending on many factors, including the recentness of last ejaculation, the average warmth of the testicles, the degree and length of time of sexual excitement prior to ejaculation, the age, testosterone level, and general fertility of the subject, and the total volume of seminal fluid. Also, the use of marijuana and other substances may kill or damage sperm.
The ejaculation reflex is caused by the sympathetic nervous system, while erection of the penis is caused by the parasympathetic nervous system. Most men experience a lag time of some half-hour or so between the ability to ejaculate consecutively. During this refractory period it is difficult or impossible to attain an erection, because the sympathetic nervous system counteracts the effects of the parasympathetic nervous system.
There are wide variations in how long sexual intercourse can last before ejaculation occurs. Studies have shown that most men can only avoid ejaculation during active thrusting for five minutes or less. A minority can ejaculate more or less at will, and delay ejaculation for an hour or longer during sexual intercourse.
When a man ejaculates before he wants to it is called premature ejaculation. If a man is unable to ejaculate in a timely manner after prolonged sexual stimulation, in spite of his desire to do so, it is called delayed ejaculation or anorgasmia. An orgasm that is not accompanied by ejaculation is known as a dry orgasm.
How does an erection occur?
The penis contains two chambers called the corpora cavernosa, which run the length of the organ. A spongy tissue fills the chambers. The corpora cavernosa are surrounded by a membrane, called the tunica albuginea. The spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and arteries. The urethra, which is the channel for urine and ejaculate, runs along the underside of the corpora cavernosa and is surrounded by the corpus spongiosum.
Erection begins with sensory or mental stimulation, or both. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the spaces. The blood creates pressure in the corpora cavernosa, making the penis expand. The tunica albuginea helps trap the blood in the corpora cavernosa, thereby sustaining erection. When muscles in the penis contract to stop the inflow of blood and open outflow channels, erection is reversed.
Arteries -top- and veins -bottom- penetrate the long, filled cavities running the length of the penis--the corpora cavernosa and the corpous spongiosum. Erection occurs when relaxed muscles allow the corpora cavernosa to fill with excess blood fed by the arteries, while drainage of blood through the veins is blocked.
