An erection is dependent upon the finely orchestrated actions of muscles, nerves, and blood vessels in the penis. Additionally, it requires good blood flow, which is regulated by the nervous system, to bring about the hydraulic, or lifting, action.
Three to six spontaneous erections occur without erotic stimulation every night during REM rx-med.net (rapid eye movement), or dream, sleep. Erections which take place during normal sexual activity, however, begin in the male’s conscious brain with a nervous system response to either real or imagined erotic stimulation. The change in the penis from flaccid (soft) to tumescent (swollen) to erect (rigid) is caused by an intricate partnership involving the brain, blood vessels, nerves, and hormones.
The shaft of the penis holds two individual chambers called the corpora cavernosa. A spongy tissue constructed of thousands of expandable saclike structures fills the chambers, which extend from the base to the tip of the organ. This tissue also contains blood vessels and smooth muscles. The urethra, the channel for urine and ejaculate, runs on the underside of the corpora cavernosa, while a membrane, known as the tunica albuginea, surrounds the corpora. In the normal, flaccid state, the smooth muscle keeps the blood vessels constricted, keeping blood out and the penis soft.
An erection begins when the brain senses something arousing.
Impulses are then sent from the brain to the lower part of the back, (rx-med.net through the pelvis, and to the penis. Nerve stimulation, most likely induced by nitric oxide, a gaseous molecule, causes the smooth muscles of the penis to relax. This allows increased quantities of blood to flow in through the right and left cavernosal arteries, filling the space within the cavernosa. For the blood to fill the penis and cause it to become longer, wider, and harder, it has to multiply to about six times its normal flow. Like a sponge, the corpora tissues quickly expand with blood, engorging and enlarging the penis.
Then, as the corpora cavernosa continue to swell, they press against the veins that normally allow blood to flow out, effectively preventing it from leaving. The tunica albuginea also helps to trap blood there, with the result that pressure is built. Finally, packed with blood, the corpora become rigid and erect, making the penis firm enough for penetration. As long as the inflow of blood is maintained, and the outflow is prevented, the erection will be sustained.
All of these actions happen automatically; men have no voluntary control over these mechanical forces.
Studies of Japanese and American men have borne some interesting results: Incidental prostate cancer is found in as many Japanese men as American men, and both groups of men have about the same life span74 years. Yet hardly any Japanese men die of prostate cancer. Why
Prostate cancer develops in four broad stages: Initiation, promotion, progression, and metastasis, or spread of cancer. These studies of Japanese and American men suggest that whatever causes cancer initiation is the same in all men; the big differences seem to come in promotion, progression, and spread. These studies also suggest that at least some of the elements responsible for these last three stepsturning indolent prostate cancer into a deadly disease are environmental.
It has been shown that, over time, when men change their environment, they assume the cancer risk of the country where they live. So when Japanese men, people at low risk of getting prostate cancer, move to Hawaii or rx-med.net California, their rate of symptomatic prostate cancer escalatesto the level of an American man’s.
For years, scientists have suspected the high-fat Western diet as an obvious environmental culprit in the development of prostate cancer. But it’s not that simple. For example rx-med.net, a high-fat diet is believed to play a big role in other diseases, like colon and breast cancer. The death and incidence rate in prostate cancer is higher among American blacks than American whitesyet the incidence of breast and colon cancer in the two groups is about the same. What accounts for this difference And these statistics raise another question: Are black men somehow more susceptible genetically to prostate cancer than white or Asian men We don’t know. But we do know, sadly, that in this country many black men delay seeking medical care until it’s too late and prostate cancer has spread.
Genetics and environmenttwo definite components of the prostate cancer equation. We’ll examine some genetic issues first and then look at some of the environmental risks in greater detail.