Ejaculation

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Ejaculation
Ejaculation educational seq 4.png
A human male ejaculating
Identifiers
MeSH D004542
TE E1.0.0.0.0.0.10
Anatomical terminology

Ejaculation is the discharge of semen (the ejaculate; normally containing sperm) from the penis through the urethra. [1] [2] [3] It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. After forming an erection, many men emit pre-ejaculatory fluid during stimulation prior to ejaculating. Ejaculation involves involuntary contractions of the pelvic floor and is normally linked with orgasm. It is a normal part of male human sexual development.

Contents

It can occur spontaneously during sleep (a nocturnal emission or "wet dream"). In rare cases, ejaculation occurs because of prostatic disease. Anejaculation is the condition of being unable to ejaculate. Dysejaculation is an ejaculation that is painful or uncomfortable. Retrograde ejaculation is the backward flow of semen into the bladder rather than out of the urethra. Premature ejaculation happens shortly after initiating sexual activity, and hinders prolonged sexual intercourse. A vasectomy alters the composition of the ejaculate as a form of birth control.

Phases

Stimulation

The normal precursor to ejaculation is sexual arousal of the male, leading to the erection of the penis, though not all arousals or erections lead to ejaculation, and ejaculation does not require erection. Penile sexual stimulation during masturbation or vaginal, anal, oral, manual, or non-penetrative sexual activity may provide the necessary stimulus for a man to achieve orgasm and ejaculation. With regard to intravaginal ejaculation latency, men typically reach orgasm five to seven minutes after the start of penile-vaginal intercourse, taking into account their desire and that of their partners, but 10 minutes is also a common intravaginal ejaculation latency. [4] [5] Prolonged stimulation either through foreplay (kissing, petting and direct stimulation of erogenous zones before penetration during intercourse) or stroking (during masturbation) leads to adequate arousal and production of pre-ejaculatory fluid. Infectious agents (including HIV) can be present in pre-ejaculate. [6]

Emission phase

During the emission phase of ejaculation, sperm travels from the epididymis through the vas deferens mixing with fluids from the male accessory glands as it enters the urethra. During the expulsion phase, rhythmic contractions of the pelvic floor and bulbospongiosus muscles expel the semen from the penis through the urinary meatus in several spurts. Ejaculation anatomy en.svg
During the emission phase of ejaculation, sperm travels from the epididymis through the vas deferens mixing with fluids from the male accessory glands as it enters the urethra. During the expulsion phase, rhythmic contractions of the pelvic floor and bulbospongiosus muscles expel the semen from the penis through the urinary meatus in several spurts.
Video of a human male ejaculating

Once the penis has achieved sufficient stimulation for the man to reach orgasm, ejaculation begins. [7] The initial stage of ejaculation, called emission, is controlled by a reflex in the sympathetic spinal cord. Sperm undergo their final developmental changes within the epididymis, where they are held until being ejaculated. [8]

Expulsion phase

Ejaculation reaches its peak in the expulsion phase, which involves the discharge of semen from the urethral opening. This ejection is driven by coordinated contractions of the pelvic muscles, including the bulbospongiosus and pubococcygeus muscles. For the semen to be expelled out of the penis, the bladder neck stays shut while the external urethral sphincter is relaxed. These rhythmic contractions are part of the male orgasm [9] under the control of a spinal reflex at the level of the spinal nerves S2–4 via the pudendal nerve. Although the external sphincter and pelvic muscles can be voluntarily controlled, any voluntary control during semen expulsion is not evident. The expulsion phase is considered an extension of the emission phase, triggered by reaching a certain level of spinal nerve activation. [10] The typical male orgasm lasts several seconds.

Premature ejaculation is when ejaculation occurs before it is desired. Otherwise, if a man is unable to ejaculate after prolonged sexual stimulation in spite of his desire, it is called delayed ejaculation or anorgasmia. An orgasm that is not accompanied by ejaculation is known as a dry orgasm.

At start of orgasm, pulses of semen begin to flow from the urethra, reach a peak of discharge and then diminish in flow. The typical orgasm consists of 10 to 15 contractions, although the man may not be consciously aware of so many. After the first contraction, ejaculation continues to completion involuntarily. During this stage ejaculation cannot be stopped. The rate of contractions gradually slows throughout the orgasm. Initial contractions occur on average every 0.6 seconds with an increasing increment of 0.1 seconds per contraction. Contractions of most men proceed at regular rhythmic intervals through their duration. Many men also experience irregular contractions at the end of the orgasm. [11]

Ejaculation usually begins during the first or second contraction of orgasm. For most men, the first ejection occurs during the second contraction, which is typically the largest, expelling 40% or more of total semen discharge. After this peak, the quantity of semen emitted by the penis diminishes as the contractions lessen in intensity. The muscle contractions of the orgasm can continue after ejaculation with no additional semen discharge. A small sample study of seven men showed an average of seven 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. [12]

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". [13] Masters and Johnson report ejaculation distance to be no greater than 30–60 cm (12–24 in). [14] During the series of contractions that accompany ejaculation, semen is propelled from the urethra at 500 cm/s (200 in/s), close to 18 km/h (11 mph). [9]

Refractory period

Most men experience a refractory period immediately following an orgasm, during which they are unable to achieve another erection, and a longer period before they are capable of achieving another ejaculation. During this time a male feels a deep and often pleasurable sense of relaxation, usually in the groin and thighs. The length of the refractory period varies considerably, even for a given individual. Age affects the recovery time, with younger men recovering faster than older men, though not always. [14]

Whereas some men have refractory periods of 15 minutes or more, others are able to experience sexual arousal immediately after ejaculation. A short recovery period may allow partners to continue sexual play relatively uninterrupted by ejaculation. Some men may experience their penis becoming hypersensitive to stimulation after ejaculation, which can make sexual stimulation unpleasant even while they may be sexually aroused.

Some men are able to achieve multiple orgasms, with or without the typical sequence of ejaculation and refractory period. Some of those men report not noticing refractory periods, or are able to maintain erection by "sustaining sexual activity with a full erection until they passed their refractory time for orgasm when they proceeded to have a second or third orgasm". [15]

Volume

The force and amount of semen that is ejected during ejaculation varies widely among men, containing between 0.1 and 10 milliliters [16] (for comparison, a teaspoon holds 5 ml and a tablespoon, 15 ml). Adult semen volume is affected by the time that has passed since his previous ejaculation; larger semen volumes develop with longer abstinence. The duration of the stimulation leading to ejaculation can affect the volume. [17] Abnormally low semen volume is known as hypospermia and abnormally high semen volume is called hyperspermia. One possible underlying cause of low volume or complete lack of semen is ejaculatory duct obstruction. It is normal for the amount of semen to diminish with age.

Quality

The number of sperm in an ejaculation varies widely, depending on many factors including the time since the previous ejaculation, [18] age, stress levels, [19] and testosterone. Longer time of sexual stimulation immediately preceding ejaculation can result in higher concentration of sperm. [17] An unusually low sperm count, distinguished from low semen volume, is known as oligospermia, and the absence of any sperm from the semen is termed azoospermia.

Development

During puberty

Diagram of the male pelvic and reproductive organs Male anatomy 1.png
Diagram of the male pelvic and reproductive organs

The first ejaculation in males often occurs about 12 months after the onset of puberty, generally through masturbation or nocturnal emission (wet dreams). This first semen volume is small. The typical ejaculation over the following three months produces less than 1 ml of semen. The semen produced during early puberty is also typically clear. After ejaculation this early semen remains jellylike and, unlike semen from mature males, fails to liquefy. A summary of semen development is shown in Table 1.

Most first ejaculations (90%) lack sperm. Of the few early ejaculations that do contain sperm, the majority of sperm (97%) lack motion. The remaining sperm (3%) have abnormal motion. [20]

As the male proceeds through puberty, the semen develops mature characteristics with increasing quantities of normal sperm. Semen produced 12 to 14 months after the first ejaculation liquefies after a short period of time. Within 24 months of the first ejaculation, the semen volume and the quantity and characteristics of the sperm match that of adult male semen. [20]

Semen development during puberty
Time after first
ejaculation (months)		Average volume
(milliliter)		LiquefactionAverage sperm concentration
(million sperm/milliliter)
00.5No a 0
61.0No a 20
122.5No/Yes b 50
183.0Yes c 70
243.5Yes c 300

^a Ejaculate is jellylike and fails to liquefy.
^b Most samples liquefy. Some remain jellylike.
^c Ejaculate liquefies within an hour.

Control from the central nervous system

There is a central pattern generator in the spinal cord, made up of groups of spinal interneurons, that is involved in the rhythmic response of ejaculation. This is known as the spinal generator for ejaculation. [21]

To map the neuronal activation of the brain during the ejaculatory response, researchers have studied the expression of c-Fos, a proto-oncogene expressed in neurons in response to stimulation by hormones and neurotransmitters. [22] Expression of c-Fos in the following areas has been observed: [23] [24]

Hands-free ejaculation

Although uncommon, some men can achieve ejaculations during masturbation without any manual stimulation. Such men usually do it by tensing and flexing their abdominal and buttocks muscles along with vigorous fantasizing. Others may do it by relaxing the area around the penis, which may result in harder erections especially when hyper aroused. [25] Hands-free ejaculation can also be achieved by prostate stimulation alone, either internally (with the use of sex toys, fingers or performing anal sex or pegging) or externally (such as perineum massages), [26] [27] although prostate orgasms without ejaculation (dry orgasms) are also possible. [28]

Perineum pressing and retrograde ejaculation

Perineum pressing results in an ejaculation which is purposefully held back by pressing on either the perineum or the urethra to force the seminal fluid to remain inside. In such a scenario, the seminal fluid stays inside the body and goes to the bladder. Some people do this to avoid making a mess by keeping all the semen inside. [29] As a medical condition, it is called retrograde ejaculation. [30]

Health issues

For most men, no detrimental health effects have been determined from ejaculation itself or from frequent ejaculations,[ citation needed ] though sexual activity in general can have health or psychological consequences. A small fraction of men have a disease called postorgasmic illness syndrome (POIS), which causes severe muscle pain throughout the body and other symptoms immediately following ejaculation. The symptoms last for up to a week. [31] [32] [33] Some doctors speculate that the frequency of POIS "in the population may be greater than has been reported in the academic literature", [34] and that many POIS sufferers are undiagnosed. [35]

It is not clear whether frequent ejaculation has any effect on the risk of prostate cancer. [36] [37] [38] Two large studies examining the issue were [39] [40] [41] "Ejaculation Frequency and Subsequent Risk of Prostate Cancer" [42] and "Sexual Factors and Prostate Cancer". [43] These suggest that frequent ejaculation after puberty offers some reduction of the risk of prostate cancer. The US study involving 29,342 US men aged 46 to 81 years [42] suggested that "high ejaculation frequency was related to decreased risk of total prostate cancer". [42] An Australian study involving 1,079 men with prostate cancer and 1,259 healthy men found that "there is evidence that the more frequently men ejaculate between the ages of 20 and 50, the less likely they are to develop prostate cancer":

[T]he protective effect of ejaculation is greatest when men in their twenties ejaculated on average seven or more times a week. This group were one-third less likely to develop aggressive prostate cancer when compared with men who ejaculated less than three times a week at this age. [44]

Other animals

In mammals and birds, multiple ejaculation is commonplace. [45] [46] [ clarification needed ] During copulation, the two sides of a short-beaked echidna's penis are used sequentially. Alternating between the two sides allows for persistent stimulation to induce ejaculation without impeding the refractory period. [47]

In stallions, ejaculation is accompanied by a motion of the tail known as "tail flagging". [48] When a male wolf ejaculates, his final pelvic thrust may be slightly prolonged. [49] A male rhesus monkey usually ejaculates less than 15 seconds after sexual penetration. [50] The first report and footage of spontaneous ejaculation in an aquatic mammal was recorded in a wild Indo-Pacific bottlenose dolphin near Mikura Island, Japan, in 2012. [51]

In horses, sheep, and cattle, ejaculation occurs within a few seconds, but in boars, it can last for five to thirty [52] minutes. [53] Ejaculation in boars is stimulated when the spiral-shaped penis interlocks with the female's cervix. [54] A mature boar can produce 250–300 ml (8.8–10.6 imp fl oz; 8.5–10.1 US fl oz) of semen during one ejaculation. [53] In llamas and alpacas, ejaculation occurs continuously during copulation. [55]

The semen of male dogs is ejaculated in three separate phases. [56] The last phase of a male canine's ejaculation occurs during the copulatory tie, and contains mostly prostatic fluid. [57]

See also

Related Research Articles

Orgasm or sexual climax is the sudden release of accumulated sexual excitement during the sexual response cycle, characterized by intense sexual pleasure resulting in rhythmic, involuntary muscular contractions in the pelvic region. Orgasms are controlled by the involuntary or autonomic nervous system and experienced by both males and females; the body's response includes muscular spasms, a general euphoric sensation, and, frequently, body movements and vocalizations. The period after orgasm is typically a relaxing experience, after the release of the neurohormones oxytocin and prolactin, as well as endorphins.

<span class="mw-page-title-main">Sexual intercourse</span> Penetrative sexual activity for reproduction or sexual pleasure

Sexual intercourse is a sexual activity typically involving the insertion and thrusting of the male penis inside the female vagina for sexual pleasure, reproduction, or both. This is also known as vaginal intercourse or vaginal sex. Sexual penetration has been known by humans since the dawn of time, and has been an instinctive form of sexual behaviour and psychology among humans. Other forms of penetrative sexual intercourse include anal sex, oral sex, fingering and penetration by use of a dildo, and vibrators. These activities involve physical intimacy between two or more people and are usually used among humans solely for physical or emotional pleasure. They can contribute to human bonding.

<span class="mw-page-title-main">Prostate</span> Gland of the male reproductive system

The prostate is an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemically, and physiologically. Anatomically, the prostate is found below the bladder, with the urethra passing through it. It is described in gross anatomy as consisting of lobes and in microanatomy by zone. It is surrounded by an elastic, fibromuscular capsule and contains glandular tissue, as well as connective tissue.

<span class="mw-page-title-main">Pre-ejaculate</span> Clear fluid emitted from the urethra of the penis during arousal

Pre-ejaculate is a clear, colorless, viscous fluid that is emitted from the urethra of the penis during sexual arousal and in general during sexual activity. It is similar in composition to semen but has distinct chemical differences. The presence of sperm in the fluid is variable from low to absent. Pre-ejaculate functions as a lubricant and an acid neutralizer.

A wet dream, sex dream, or sleep orgasm, is a spontaneous occurrence of sexual arousal during sleep that includes ejaculation and orgasm for a male, and vaginal lubrication and/or orgasm for a female.

<span class="mw-page-title-main">Prostate massage</span> Massage of the prostate gland via the rectum or perineum

Prostate massage is the massage or stimulation of the male prostate gland for medical purposes or sexual stimulation.

Premature ejaculation (PE) is a male sexual dysfunction that occurs when a male expels semen soon after beginning sexual activity, and with minimal penile stimulation. It has also been called early ejaculation, rapid ejaculation, rapid climax, premature climax and (historically) ejaculatio praecox. There is no uniform cut-off defining "premature", but a consensus of experts at the International Society for Sexual Medicine endorsed a definition of around one minute after penetration. The International Classification of Diseases (ICD-10) applies a cut-off of 15 seconds from the beginning of sexual intercourse.

Coitus reservatus, also known as sexual continence, is a form of sexual intercourse in which a male does not attempt to ejaculate within his partner, avoiding the seminal emission. It is distinct from death-grip syndrome, wherein a male has no volition in his emissionless state.

<span class="mw-page-title-main">Retrograde ejaculation</span> Redirection of ejaculated semen into the urinary bladder

Retrograde ejaculation occurs when semen which would be ejaculated via the urethra is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts before ejaculation, inhibiting urination and preventing a reflux of semen into the bladder. The semen is forced to exit via the urethra, the path of least resistance. When the bladder sphincter does not function properly, retrograde ejaculation may occur. It can also be induced deliberately by a male as a primitive form of male birth control or as part of certain alternative medicine practices. The retrograde-ejaculated semen is excreted from the bladder during the next urination.

<span class="mw-page-title-main">Ejaculatory duct</span> Male anatomical structures

The ejaculatory ducts are paired structures in the male reproductive system. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra above the seminal colliculus. During ejaculation, semen passes through the prostate gland, enters the urethra and exits the body via the urinary meatus.

<span class="mw-page-title-main">Facial (sexual act)</span> Sexual activity involving ejaculating on the face of another

A facial is a sexual activity in which a man ejaculates semen onto the face of one or more sexual partners. A facial is a form of non-penetrative sex, though it is generally performed after some other means of sexual stimulation, such as vaginal sex, anal sex, oral sex, manual sex or masturbation. Facials are regularly portrayed in pornographic films and videos, often as a way to close a scene.

The human sexual response cycle is a four-stage model of physiological responses to sexual stimulation, which, in order of their occurrence, are the excitement, plateau, orgasmic, and resolution phases. This physiological response model was first formulated by William H. Masters and Virginia E. Johnson, in their 1966 book Human Sexual Response. Since that time, other models regarding human sexual response have been formulated by several scholars who have criticized certain inaccuracies in the human sexual response cycle model.

<span class="mw-page-title-main">Semen collection</span> Process of obtaining semen from male animals

Semen collection refers to the process of obtaining semen from human males or other animals with the use of various methods, for the purposes of artificial insemination, or medical study. Semen can be collected via masturbation, prostate massage, artificial vagina, penile vibratory stimulation (vibroejaculation) and electroejaculation. Semen can be collected from endangered species for cryopreservation of genetic resources.

Hypospermia is a condition in which a man has an unusually low ejaculate volume, less than 1.5 mL. It is the opposite of hyperspermia, which is a semen volume of more than 5.5 mL. It should not be confused with oligospermia, which means low sperm count. Normal ejaculate when a man is not drained from prior sex and is suitably aroused is around 1.5–6 mL, although this varies greatly with mood, physical condition, and sexual activity. Of this, around 1% by volume is sperm cells. The U.S.-based National Institutes of Health defines hypospermia as a semen volume lower than 2 mL on at least two semen analyses.

Anejaculation is the pathological inability to ejaculate despite an erection in males, with (orgasmic) or without (anorgasmic) orgasm.

Delayed ejaculation (DE) is a man's inability or persistent difficulty in achieving orgasm, despite typical sexual desire and sexual stimulation. Generally, a man can reach orgasm within a few minutes of active thrusting during sexual intercourse, whereas a man with delayed ejaculation either does not have orgasms at all or cannot have an orgasm until after prolonged intercourse which might last for 30–45 minutes or more. Delayed ejaculation is closely related to anorgasmia.

<span class="mw-page-title-main">Masturbation</span> Sexual stimulation of ones own genitals

Masturbation is a form of autoeroticism in which a person sexually stimulates their own genitals for sexual arousal or other sexual pleasure, usually to the point of orgasm. Stimulation may involve use of hands, everyday objects, sex toys, or more rarely, the mouth. Masturbation may also be performed with a sex partner, either masturbating together or watching the other partner masturbate.

<span class="mw-page-title-main">Human penis</span> Human male external reproductive organ

In human anatomy, the penis is an external sex organ through which males urinate and ejaculate. Together with the testes and surrounding structures, the penis functions as part of the male reproductive system.

<span class="mw-page-title-main">Semen</span> Reproductive biofluid of male or hermaphroditic animals

Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoa. Spermatozoa are secreted by the male gonads and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. In placental mammals, semen also contains secretions from the male accessory glands and is discharged from the penis through the urethral orifice during ejaculation. In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa and provide a medium through which they can move or "swim". The fluid is adapted to be discharged deep into the vagina, so the spermatozoa can pass into the uterus and form a zygote with an egg.

<span class="mw-page-title-main">Sexuality after spinal cord injury</span> Aspect of human sexuality

Although spinal cord injury (SCI) often causes sexual dysfunction, many people with SCI are able to have satisfying sex lives. Physical limitations acquired from SCI affect sexual function and sexuality in broader areas, which in turn has important effects on quality of life. Damage to the spinal cord impairs its ability to transmit messages between the brain and parts of the body below the level of the lesion. This results in lost or reduced sensation and muscle motion, and affects orgasm, erection, ejaculation, and vaginal lubrication. More indirect causes of sexual dysfunction include pain, weakness, and side effects of medications. Psycho-social causes include depression and altered self-image. Many people with SCI have satisfying sex lives, and many experience sexual arousal and orgasm. People with SCI may employ a variety of adaptations to help carry on their sex lives healthily, by focusing on different areas of the body and types of sexual acts. Neural plasticity may account for increases in sensitivity in parts of the body that have not lost sensation, so people often find newly sensitive erotic areas of the skin in erogenous zones or near borders between areas of preserved and lost sensation.

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