Everything about Ejaculate totally explained
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's due to prostatic disease. Ejaculation may occur spontaneously during
sleep (a
nocturnal emission).
Anejaculation is the condition of being unable to ejaculate.
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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.
Ejaculation proper
These rhythmic contractions are part of the male orgasm. They are generated by the
bulbospongiosus muscle. 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, each bringing an extremely pleasurable sensation to the head of the penis. Once the first contraction has taken place, there's nothing the male can do to prevent ejaculation taking place. 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.
Semen content
Sartoli cells, which nurture and support developing spermatocytes, secrete a fluid into seminiferous tubules that helps transport spermatozoa to the genital ducts. The Ductuli Efferentes posses cuboidal cells with microvilli and lysosomal granules that modify the semen by reabsorbing some fluid. Once the semen enters the Ductus Epididymis the principle cells, which contain pinocytotic vessels indicating fluid reabsorption, secrete glycerophosphocholine which most likely inhibits premature
capacitation. The accessory genital ducts, the
seminal vesicle,
prostate glands, and the
bulbourethral glands, produce most of the seminal fluid. The seminal vesicles produce a yellowish viscous fluid rich in fructose and other substances that makes up ~70% of human ejaculate. The prostatic secretion, influenced by dihydrotestosterone, is a whitish, thin fluid containing proteolytic enzymes, citric acid, acid phosphatase and lipids. The bulbourethral glands secrete a clear secretion into the lumen of the
urethra to lubricate it.
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 sample study of seven men showed between 26 and 60 percent of the contractions during orgasm were accompanied by a spurt of semen.
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's difficult or impossible to attain an
erection, because the
sympathetic nervous system counteracts the effects of the parasympathetic nervous system.
Stimulation
There are wide variations in how long sexual stimulation can last before ejaculation occurs.
When a man ejaculates before he wants to it's 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's called
delayed ejaculation or
anorgasmia. An orgasm that isn't accompanied by ejaculation is known as a
dry orgasm.
Volume
The
force and amount of ejaculate vary widely from male to male. A normal ejaculation may contain anywhere from 1.5 to 5
milliliters. 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's these ejaculations which are important, not the mechanism. Also, the duration of the stimulation leading up to the ejaculation can affect the volume. Abnormally low volume is known as
hypospermia, though it's normal for the amount of ejaculate to diminish with age.
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, 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 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
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.
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. Expression of c-fos in the following areas have been observed:,
- 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
Fertilization
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're 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 artificial insemination.
Further Information
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