Ejaculation is the process whereby semen is ejected from a penis and is generally accompanied by an orgasm. Ejaculation also occurs spontaneously during sleep (nocturnal emission or what is generally referred to as “wet dream”) and seldom occurs as a result of prostatic disease. Ejaculation is basically controlled by the central nervous system, and happens when friction on the genitalia and other forms of sexual stimulation provide impulses that are sent up the spinal cord and into the brain.
Ejaculation has two basic phases and these are the emission and ejaculation itself. During the emission phase, semen (sperm and seminal fluids from the seminal vesicles) is deposited into the posterior urethra as the vas deferens (the two ducts that store and transport sperm from the testes) contracts to squeeze the semen toward the base of the penis through the prostate gland. Equally at the same time, the internal sphincter of the urinary bladder is closed, thus preventing the retrograde passage of the semen into the bladder and also preventing urine from mixing with the semen. It is suggested that the sensation at the “point of ejaculatory inevitability” corresponds to the emission phase.
Emission is immediately followed by the second phase, the ejaculation proper. During this process, the semen is forcefully propelled along the urethra and out of the penis through the rhythmic contraction of the muscles of the urethra in conjunction with those of the pelvic floor muscles. As a precursor to ejaculatory orgasm, some few drops of a clear alkaline fluid may trickle out of the penis from the prostate and other glands to lubricate the urethra and pave way for the semen. This is often referred to as the “pre-ejaculate”.
Ejaculation and orgasm usually occur simultaneously in men even though ejaculation and orgasm are two separate phenomenona. The rhythmic contractions during the ejaculation process are part of the male orgasm. On an average, male orgasms can last from a few seconds up to 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 and once the first contraction occurs, ejaculation will continue involuntarily to completion.
Ejaculation begins during the first or second contraction of orgasm. For most men the first spurt occurs during the second contraction. The first or second spurt is usually the largest and can contain 40 percent or more of the total ejaculates volume. After this peak, the flow of each subsequent pulse diminishes. When the flow ends, the muscle contractions of the orgasm continue with no additional semen discharge. Expulsion is mediated by the somatic nervous system. Orgasm is associated in timing with the expulsive phase.
With each ejaculation, men release approximately about 11/2 to 2 teaspoons of semen containing about 40 to 600 million sperm cells. This amount decreases or increases based on the time since the last ejaculation, the warmth of the testicles, the degree of sexual excitement, testosterone levels, age and the man’s general fertility level.
There is however little knowledge about the physiological mechanism and neurobiology underlying the sensation of orgasm. It is a complex response involving the whole body. During orgasm, there are changes in the genitalia, in the skeletal muscle tone (as evidenced by the usual spastic contractions of the feet), contractions of facial musculature, vocal reactions (moaning and sighing), semi-voluntary movements, general cardiovascular and respiratory changes, somatic sensory experiences, and an altered consciousness. These intense feelings of pleasure and desire that accompany orgasm are mediated by the brain.
Nevertheless, there are certain dysfunctions that often affect ejaculation and these include premature ejaculation, retarded ejaculation and retrograde ejaculation. The most common of these dysfunctions is premature ejaculation, which causes ejaculation to occur before or shortly after penetration. Retarded ejaculation is when ejaculation does not occur after orgasm while retrograde ejaculation is caused when the semen travels back into the bladder during orgasm.
In summary, these are nine quick facts about Ejaculation you need to be aware of:
- Average volume of semen per ejaculation: 2 to 6 ml (0.41 to 1.22 US teaspoons)
- Average number of times a man will ejaculate in his lifetime: 5,000
- Average total amount of lifetime ejaculate: 17 litres or 18 quarts
- Average number of calories in a teaspoon of semen: 7
- Average duration of orgasm: 17 seconds
- Average number of sperm cells in the ejaculate of a healthy man: 40 million to 600 million
- Distance sperm travels to fertilize an egg: 7.5-10 centimetres or 3-4 inches
- Sperm lifespan: 2.5 months from development to ejaculation
- Sperm lifespan after ejaculation: 30 seconds to 6 days depending on conditions