Ejaculation

Ejaculation is the discharge of semen (normally containing sperm) from the male reproductory tract, usually accompanied by orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases, ejaculation occurs because of prostatic disease. Ejaculation may also occur spontaneously during sleep (a nocturnal emission or 'wet dream'). Anejaculation is the condition of being unable to ejaculate. Ejaculation is usually very pleasurable for men; dysejaculation is an ejaculation that is painful or uncomfortable. Retrograde ejaculation is the condition where semen travels backwards into the bladder rather than out the urethra. A usual precursor to ejaculation is the sexual arousal of the male, leading to the erection of the penis, though not every arousal nor erection leads to ejaculation. Penile sexual stimulation during masturbation or vaginal, anal, oral, or non-penetrative sexual activity may provide the necessary stimulus for a man to achieve orgasm and ejaculation. With regard to intravaginal ejaculation latency time, men typically reach orgasm 5–7 minutes after the start of penile-vaginal intercourse, taking into account their desires and those of their partners, but 10 minutes is also a common intravaginal ejaculation latency time. A prolonged stimulation either through foreplay (kissing, petting and direct stimulation of erogenous zones before penetration during intercourse) or stroking (during masturbation) leads to an adequate amount of arousal and production of pre-ejaculatory fluid. While the presence of sperm in pre-ejaculatory fluid is thought to be rare, sperm from an earlier ejaculation, still present in the urethra, may be picked up by pre-ejaculatory fluid. In addition, infectious agents (including HIV) can often be present in pre-ejaculate. Premature ejaculation is when ejaculation occurs before the desired time. 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. When a man has achieved a sufficient level of stimulation, the orgasm and ejaculation begins. At that point, under the control of the sympathetic nervous system, semen containing sperm is produced (emission). The semen is ejected through the urethra with rhythmic contractions. These rhythmic contractions are part of the male orgasm. They are generated by the bulbospongiosus and pubococcygeus muscles under the control of a spinal reflex at the level of the spinal nerves S2–4 via the pudendal nerve. The typical male orgasm lasts several seconds. After the start of orgasm, pulses of semen begin to flow from the urethra, reach a peak discharge and then diminish in flow. The typical orgasm consists of 10 to 15 contractions, although the man is unlikely to be consciously aware of that many. Once the first contraction has taken place, ejaculation will continue to completion as an involuntary process. At this stage, ejaculation cannot be stopped. The rate of contractions gradually slows during the orgasm. Initial contractions occur at an average interval of 0.6 seconds with an increasing increment of 0.1 seconds per contraction. Contractions of most men proceed at regular rhythmic intervals for the duration of the orgasm. Many men also experience additional irregular contractions at the conclusion of the orgasm. Ejaculation usually begins during the first or second contraction of orgasm. For most men, the first ejection of semen occurs during the second contraction, while the second is typically the largest expelling 40% or more of total semen discharge. After this peak, the magnitude of semen the penis emits diminishes as the contractions begin to lessen in intensity. The muscle contractions of the orgasm can continue after ejaculation with no additional semen discharge occurring. A small sample study of seven men showed an average of 7 spurts of semen followed by an average of 10 more contractions with no semen expelled. This study also found a high correlation between number of spurts of semen and total ejaculate volume, i.e., larger semen volumes resulted from additional pulses of semen rather than larger individual spurts. Alfred Kinsey measured the distance of ejaculation, in 'some hundreds' of men. In three-quarters of men tested, ejaculate 'is propelled with so little force that the liquid is not carried more than a minute distance beyond the tip of the penis.' In contrast to those test subjects, Kinsey noted 'In other males the semen may be propelled from a matter of some inches to a foot or two, or even as far as five or six and (rarely) eight feet'. Masters and Johnson report ejaculation distance to be no greater than 30–60 cm (12–24 in). During the series of contractions that accompany ejaculation, semen is propelled from the urethra at 500 cm/s (200 in/s), close to 18 kilometres per hour (11 mph).