- The act of ejaculating.
- An abrupt discharge of fluid.
- The expulsion of seminal fluid from the urethra of the penis during orgasm.
- A sudden short exclamation, especially a brief pious utterance or prayer.
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Ejaculation of semen is the final outcome of a complex series of reflexes induced by sexual arousal and stimulation. The reflexes involve both the sympathetic and the parasympathetic branches of the autonomic nervous system, as well as spinal motor nerves and descending nerves from the brain. Three phases of the ejaculatory response can be defined — erection, emission, and ejaculation itself.
Erection is caused by changes in blood flow to the penis that can be induced by tactile stimulation of the genital region, particularly the glans penis, which has a high density of tactile-pressure receptors. This sensory information is relayed by sensory nerves to the lower spinal cord which, via parasympathetic nerves, causes dilation of arterioles in the penis. As a result blood inflow to the spongy sinuses increases dramatically and they become engorged. Because these erectile regions are surrounded by a strong fibrous coat, the penis becomes enlarged and rigid. Also, as the erectile tissue expands the venous outflow from the penis is compressed, so while inflow of blood increases, through flow does not, and erection results. Simultaneously, parasympathetic nerves stimulate the bulbo-urethral glands to produce a mucoid substance to aid lubrication. Erection can also occur in the absence of any tactile stimulation, when thoughts, visual cues, or emotions stimulate descending nerve pathways from the brain. These, in turn, activate the same nerves as those reflexly stimulated by sensory stimulation of the genital region.
During the second phase of the response (emission), contractions of the smooth muscle in the walls of the vasa deferentia, and the ejaculatory duct formed by their junction, push sperm into the upper part of the urethra. At the same time the seminal vesicles and prostate gland contract and release seminal fluid into the urethra. (See urogenital system)
In the third phase, ejaculation proper, which occurs at orgasm, the semen (sperm plus seminal fluid) is expelled from the posterior urethra by contractions of the muscles which surround it. During coitus ejaculation is also associated with involuntary rhythmic thrusting of the pelvis. The role of the sympathetic branch of the autonomic nervous system at this point is to contract the sphincter round the neck of the bladder, so that ejaculation cannot backfire in that direction.
A feeling of intense pleasure usually accompanies ejaculation, and the whole event is known as orgasm. After this there is the resolution phase in which all the physiological changes which have occurred are reversed and a man becomes refractory to any further sexual stimulation for a while. This period can last from a few minutes to several hours.
Any interference with the relevant spinal reflexes can cause impotence and other sexual dysfunction, although libido will be unaffected. The central nervous system plays an important role in regulating the sexual response, not only in normal individuals but also in cases of disordered sexual function. Whilst sexual arousal can be stimulated or enhanced by visual or other inputs of a sexual nature in the absence of tactile genital stimulation, conversely the sexual response may be suppressed by the central nervous system, either consciously or subconsciously. This can lead to impotence, loss of sexual interest, premature ejaculation, ejaculatory failure, or a loss of the usual generalized accompaniments of orgasm. These are all common defects of this complex reflex response and may have a psychogenic basis in some patients. They are often amenable to behavioural therapy.
— Saffron Whitehead
Forcible, sudden expulsion; especially expulsion of semen from the male urethra, a reflex action that occurs as a result of sexual stimulation. Includes lubricating fluid from bulbourethral glands, prostatic and seminal vesicular fluids and semen. Called also seminal ejaculation.
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.
The process of ejaculation is a very intense sensation and the climax of the male orgasm (French
"la petite mort" - the little death), which is extremely pleasurable and satisfying.
Each spurt 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. During
sexual intercourse or masturbation, most males
will find it difficult to resist the psychological urge to continue the stimulation of the penis to the point of ejaculation once
the feeling of orgasm becomes imminent.[citation needed]
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. 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.[1]
These rhythmic contractions are part of the male orgasm. The typical male orgasm lasts about 17 seconds but can vary from a few seconds up to about a minute. 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. 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 second 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.[2]
Semen begins to spurt from the penis during the first or second contraction of orgasm. For most men the first spurt occurs during the second contraction. A small study of seven men found the initial spurt occurring on the first contraction for 2 men and occurring on the second contraction for 5 men. This same study showed between 26 and 60 percent of the contractions during orgasm were accompanied by a spurt of semen.[3]
The force and amount of ejaculate vary widely from male to male. A normal ejaculation may contain anywhere from 1.5 to 5 milliliters.[4] 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 masturbation 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. [5] 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.
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, 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.
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.
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.
The first ejaculation in males occurs about 12 months after the onset of puberty. This first ejaculate 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 liquify. Most first ejaculations (90 percent) 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. [6]
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. [7]
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 [8] Expression of c-fos in the following areas have been observed: [9],[10]
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.
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".
| Physiology, endocrinology, sex: Reproductive physiology and endocrinology | |
|---|---|
| Menstrual cycle/Estrous cycle | Menstruation - Follicular phase - Ovulation - Luteal phase |
| Gametogenesis | Spermatogenesis -Oogenesis |
| Sexuality | Human sexual
behavior - Sexual intercourse - Erection -
Ejaculation - Orgasm - Insemination - Fertilisation/ |
| Lifespan | Prenatal development - Sexual dimorphism - Sexual differentiation - Puberty (Menarche, Adrenarche) - Maternal age/Paternal age - Climacteric (Menopause, Andropause) |
| Eggs | Oviposition - Oviparity - Ovoviviparity - Viviparity |
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