Ejaculation

Phases

Ejaculation is preceded by sexual arousal leading to penile erection, though not all erections result in ejaculation, and ejaculation does not require an erection. Stimulation during masturbation or various sexual activities—vaginal, anal, oral, manual, or non-penetrative—can provide the necessary stimulus. Intravaginal ejaculation latency typically ranges from five to seven minutes, though ten minutes is also common. Prolonged stimulation through foreplay or stroking leads to adequate arousal and production of pre-ejaculatory fluid, which may contain infectious agents such as HIV.

The initial stage, emission, is controlled by a reflex in the sympathetic spinal cord; sperm undergo final development in the epididymis until ejaculation. The expulsion phase involves coordinated contractions of pelvic muscles, including the bulbospongiosus and pubococcygeus, while the internal urethral sphincter remains shut and the external sphincter relaxes. These rhythmic contractions are part of the male orgasm, controlled by a spinal reflex at spinal nerves S2–4 via the pudendal nerve.

Voluntary control during expulsion is not evident. Premature ejaculation occurs before desired; delayed ejaculation or anorgasmia is the inability to ejaculate after prolonged stimulation. A dry orgasm is an orgasm without ejaculation.

Development

The first ejaculation in males typically occurs about twelve months after the onset of puberty, often through masturbation or nocturnal emission. This initial semen volume is small, and over the following three months produces less than one milliliter of semen. Early semen is clear and remains jellylike, failing to liquefy unlike mature semen. Most first ejaculations (90%) lack sperm; of those that contain sperm, 97% lack motion and the remaining 3% have abnormal motion.

As puberty progresses, semen develops mature characteristics with increasing quantities of normal sperm. Semen produced twelve to fourteen months after the first ejaculation liquefies after a short period, and within twenty-four months, semen volume and sperm characteristics match those of adult male semen. A spinal generator for ejaculation, composed of groups of spinal interneurons, is involved in the rhythmic response. Researchers have studied neuronal activation during ejaculation by observing c-Fos expression in areas including the medial preoptic area, lateral septum, bed nucleus of the stria terminalis, paraventricular nucleus of the hypothalamus, ventromedial nucleus of the hypothalamus, medial amygdala, ventral premammillary nuclei, ventral tegmental area, central tegmental field, mesencephalic central gray, peripeduncular nuclei, and parvocellular subparafascicular nucleus.

Some men can achieve hands-free ejaculation by tensing abdominal and buttocks muscles with vigorous fantasizing, or through prostate stimulation alone.

Health issues

For the vast majority of men, ejaculation—even frequent ejaculation—has not been linked to any negative health effects, though sexual activity in general can carry health or psychological risks. A rare condition called postorgasmic illness syndrome (POIS) affects a small number of men, causing severe muscle pain and other symptoms right after ejaculation that can last up to a week. Some doctors believe POIS may be more common than officially reported, with many cases going undiagnosed.

The link between frequent ejaculation and prostate cancer risk remains unclear. Two major studies suggest that frequent ejaculation after puberty might lower the risk. One study of over 29,000 American men aged 46 to 81 found that high ejaculation frequency was tied to a lower risk of total prostate cancer. Another Australian study, comparing 1,079 men with prostate cancer to 1,259 healthy men, found evidence that more frequent ejaculation between ages 20 and 50 is associated with a reduced likelihood of developing the disease.

Other animals

In many mammalian and avian species, males often ejaculate multiple times during a single mating event or repeatedly over a breeding season. During copulation, the two sides of a short-beaked echidna's penis are used sequentially to allow persistent stimulation without impeding the refractory period. In stallions, ejaculation is accompanied by tail flagging. A male wolf may have a slightly prolonged final pelvic thrust during ejaculation.

A male rhesus monkey usually ejaculates less than fifteen seconds after penetration. The first report of spontaneous ejaculation in an aquatic mammal was recorded in a wild Indo-Pacific bottlenose dolphin in 2012. In horses, sheep, and cattle, ejaculation occurs within seconds, but in boars it can last five to thirty minutes, stimulated by the penis interlocking with the cervix; a mature boar can produce 250–300 ml of semen. In llamas and alpacas, ejaculation occurs continuously during copulation.

Male dogs ejaculate in three phases, with the last phase occurring during the copulatory tie and containing mostly prostatic fluid.