Ejaculation

Un article de Vev.

Modèle:Original research Modèle:Pp-semi-protected Modèle:Twootheruses

Ejaculation is the ejecting of semen from the penis, and is usually accompanied by orgasm. It is usually the result of sexual stimulation, which may include prostate stimulation. Rarely, it is due to prostatic disease. Ejaculation may occur spontaneously during sleep (a nocturnal emission). Anejaculation is the condition of being unable to ejaculate.

Phases

Ejaculation has two phases: emission and ejaculation proper. The emission phase of the ejaculatory reflex is under control of the sympathetic nervous system, while the ejaculatory phase is under control of a spinal reflex at the level of the spinal nerves S2-4 via the pudendal nerve. A refractory period succeeds the ejaculation, and sexual stimulation precedes it.

Emission

During emission, the two ducts known as vas deferens contract to propel sperm from the epididymis where it was stored up to the ampullae at the top end of the vas deferens. The beginning of emission is typically experienced as a "point of no return," also known as point of ejaculatory inevitability. The sperm then passes through the ejaculatory ducts and is mixed with fluids from the seminal vesicles, the prostate, and the bulbourethral glands to form the semen, or ejaculate. During ejaculation proper, the semen is ejected through the urethra with rhythmic contractions.<ref>Modèle:Cite book</ref>

Ejaculation proper

www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7458658&query_hl=2&itool=pubmed_docsum The male orgasm: pelvic contractions measured by anal probe]," Archives of Sexual Behavior, 1980 Dec;9(6):503-21.</ref>//www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7458658&query_hl=2&itool=pubmed_docsum The male orgasm: pelvic contractions measured by anal probe]," Archives of Sexual Behavior, 1980 Dec;9(6):503-21.</ref>

Semen content

www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=2340374&query_hl=9&itool=pubmed_docsum Erection and ejaculation in man. Assessment of the electromyographic activity of the bulbocavernosus and ischiocavernosus muscles]", British Journal of Urology, 1990 Apr;65(4):395-402.</ref>//www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=2340374&query_hl=9&itool=pubmed_docsum Erection and ejaculation in man. Assessment of the electromyographic activity of the bulbocavernosus and ischiocavernosus muscles]", British Journal of Urology, 1990 Apr;65(4):395-402.</ref>

Refractory period

Most men experience a lag time between the ability to ejaculate consecutively, and this lag time varies among men. Age also affects the recovery time; younger men typically recover faster than older men. 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.

Stimulation

Modèle:Seealso There are wide variations in how long sexual stimulation can last before ejaculation occurs.

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.

Volume

www.focusonfertility.org/resource_swimming_conception.htm Swimming Toward Conception: The Semen Analysis]," Focus on Fertility, American Infertility Association and Organon Pharmaceuticals USA Inc.</ref> Adult ejaculate volume is affected by the amount of time that has passed since the previous ejaculation. Larger ejaculate volumes are seen with greater durations of abstinence. However, a recent Australian study has suggested a positive correlation between prostate cancer and infrequent ejaculation and/or prostate milking, which performs essentially the same function. That is, frequent ejaculation appears to reduce the risk of prostate cancer. Frequent ejaculation is more easily obtained and sustained over time with the aid of masturbation and it is these ejaculations which are important, not the mechanism.<ref>http://news.bbc.co.uk/2/hi/health/3072021.stm "Masturbation Cuts Cancer Risk," BBC News Online 16 July 2003</ref> Also, the duration of the stimulation leading up to the ejaculation can affect the volume. Abnormally low volume is known as hypospermia, though it is normal for the amount of ejaculate to diminish with age.//www.focusonfertility.org/resource_swimming_conception.htm Swimming Toward Conception: The Semen Analysis]," Focus on Fertility, American Infertility Association and Organon Pharmaceuticals USA Inc.</ref> Adult ejaculate volume is affected by the amount of time that has passed since the previous ejaculation. Larger ejaculate volumes are seen with greater durations of abstinence. However, a recent Australian study has suggested a positive correlation between prostate cancer and infrequent ejaculation and/or prostate milking, which performs essentially the same function. That is, frequent ejaculation appears to reduce the risk of prostate cancer. Frequent ejaculation is more easily obtained and sustained over time with the aid of masturbation and it is these ejaculations which are important, not the mechanism.<ref>http://news.bbc.co.uk/2/hi/health/3072021.stm "Masturbation Cuts Cancer Risk," BBC News Online 16 July 2003</ref> Also, the duration of the stimulation leading up to the ejaculation can affect the volume. Abnormally low volume is known as hypospermia, though it is normal for the amount of ejaculate to diminish with age.

Quality

Main article: Semen quality

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^{[citation needed]}, the age, testosterone level, the nutrition and especially hydration and the total volume of seminal fluid. An unusually low sperm count, not the same as low semen volume, is known as oligospermia, and the absence of any sperm from the ejaculate is termed azoospermia.

Pleasure

Each contraction is associated with a wave of immense sexual pleasure, especially in the penis and loins. The first and second convulsions are usually the most intense in sensation, and produce the greatest quantity of semen. Thereafter, each contraction is associated with a diminishing volume of semen and a milder wave of pleasure.

Ejaculate development during puberty

www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=3833078&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum</ref>//www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=3833078&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum</ref>

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 liquifies 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. <ref>Janczewski, Z. and Bablok, L.</ref>

Central nervous system control

www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=3131879&query_hl=3&itool=pubmed_docsum Expression of c-fos protein in brain: metabolic mapping at the cellular level]", Science 240:1328-1332.</ref> Expression of c-fos in the following areas have been observed: <ref> Pfaus JG and Heeb MM, "Implications of immediate-early gene induction in the brain following sexual stimulation of female and male rodents", Brain Res Bull, 1997 44:397-407.</ref>,<ref> Veening JG and Coolen LM, "Neural activation following sexual behavior in the male and female rat brain.", Behav Brain Res, 1998 92:181-193.</ref>//www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=3131879&query_hl=3&itool=pubmed_docsum Expression of c-fos protein in brain: metabolic mapping at the cellular level]", Science 240:1328-1332.</ref> Expression of c-fos in the following areas have been observed: <ref> Pfaus JG and Heeb MM, "Implications of immediate-early gene induction in the brain following sexual stimulation of female and male rodents", Brain Res Bull, 1997 44:397-407.</ref>,<ref> Veening JG and Coolen LM, "Neural activation following sexual behavior in the male and female rat brain.", Behav Brain Res, 1998 92:181-193.</ref>

• medial preoptic area (MPOA)
• lateral septum, bed nucleus of the stria terminalis
• paraventricular nucleus of the hypothalamus (PVN)
• ventromedial hypothalamus, medial amygdala
• ventral premammillary nuclei
• ventral tegmentum
• central tegmental field
• mesencephalic central gray
• peripeduncular nuclei
• parvocellular subparafascicular nucleus (SPF) within the posterior thalamus

Fertilisation

Main article: Fertilisation

During heterosexual intercourse, the vagina provides sexual stimulation to the penis, typically resulting in orgasm and ejaculation. Normally, ejaculation is required for emission of sperm; if ejaculation happens while the penis is either near or within the woman's vagina, sperm can then travel into the uterus and fertilize an egg if present, impregnating the woman. However, almost all men produce a small amount of pre-ejaculate fluid when their penis is erect and they are sexually stimulated, and this pre-ejaculate may contain some sperm which can also lead to pregnancy. For this reason, coitus interruptus may still lead to unwanted pregnancies for couples engaging in vaginal intercourse if other forms of birth control are not used as well. See also artifical insemination.

Euphemisms

Because sexual topics are often an uncomfortable topic among peers, a huge variety of euphemisms and dysphemisms have been invented to describe ejaculation and semen. For a complete list of terms, see: "Sexual slang".

See also

• Aspermia
• Azoospermia
• Coitus interruptus
• Coitus reservatus
• Female ejaculation
• Retrograde ejaculation
• Keri - ejaculation in Jewish law
• Mantak Chia - Author of many books of male sexuality.

References

Modèle:Reproductive physiologyaf:Ejakulasie ar:قذف (أحياء) bg:Еякулация cs:Ejakulace cy:Alldafliad da:Udløsning de:Ejakulation es:Eyaculación eu:Isurtze fa:انزال fr:Éjaculation hr:Ejakulacija ko:사정 (생리학) id:Ejakulasi it:Eiaculazione lt:Ejakuliacija ml:സ്ഖലനം nl:Ejaculatie ja:射精 pl:Ejakulacja pt:Ejaculação ru:Эякуляция simple:Ejaculation sk:Ejakulácia fi:Siemensyöksy sv:Ejakulation ta:விந்து தள்ளல் vi:Xuất tinh zh-yue:射精 zh:射精