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Erection
Mechanism of ErectionThe penis contains two chambers called the corpora cavernosa, which run the length of the organ (see figure below). A spongy tissue fills the chambers. The corpora cavernosa are surrounded by a membrane, called the tunica albuginea. The spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and arteries. The urethra, which is the channel for urine and ejaculate, runs along the underside of the corpora cavernosa. Erection begins with sensory or mental stimulation, or both. When a man becomes aroused through visual or physical stimulation the brain sends signals to the genital area that triggers the release of nitric oxide in the penis. This event is the catalyst that begins a chain of events leading to the erection. Nitric oxide in the penis activates the enzyme guanylate cyclase. This enzyme causes increased levels of cyclic guanosine monophosphate (cGMP). When levels of cGMP are increased in the penis this causes a smooth muscle relaxation in the pelvis and corpora cavernosa and allows increased blood flow into the corpora cavernosa. As the corpora cavernosa fills with blood it begins
to expand due to the pressure created by blood, making the
penis expand. And as it expands the arteries that normally carry blood
out of the penis become restricted and are unable to carry
blood out faster than blood is coming in. The tunica albuginea
helps trap the blood in the corpora cavernosa. With more blood coming in
and less going out the corpora cavernosa continues to expand
and harden, thus resulting in an erection. When muscles
in the penis contract to stop the inflow of blood and open outflow channels,
erection is reversed. Erectile Dysfunction ED is treatable at any age. Awareness of this fact has been growing.
Since an erection requires a precise sequence of events, ED can occur
when any of the events is disrupted. The sequence includes nerve impulses
in the brain, spinal column, and area around the penis, and response in muscles,
fibrous tissues, veins, and arteries in and near the corpora cavernosa.
Damage to nerves, arteries, smooth muscles, and fibrous tissues, often as
a result of disease, is the most common cause of ED. Diseases--such as diabetes,
kidney disease, chronic alcoholism, multiple sclerosis, atherosclerosis,
vascular disease, and neurologic disease--account for about 70 percent of
ED cases. Between 35 and 50 percent of men with diabetes experience ED.
Also, surgery (especially radical prostate surgery for cancer) can injure
nerves and arteries near the penis, causing ED. Injury to the penis, spinal
cord, prostate, bladder, and pelvis can lead to ED by harming nerves, smooth
muscles, arteries, and fibrous tissues of the corpora cavernosa. One-third of the men surveyed in a study appearing in the August 5 issue of the Annals of Internal Medicine reported having problems with an erection in the prior three months. While the incidence of erectile dysfunction (ED) increased about 5 percent each year for all men, the problem was notably less common among men leading healthy lifestyles. Being a vigorous exerciser and adding other healthy lifestyle factors such as eating nine servings of fruits and vegetables a day, not smoking, staying lean and not drinking had the effect of adding 10 years to a man's sexual status. Men who did the equivalent of three hours of running or more each week or playing five hours of singles tennis reported a 30 percent lower risk of ED, compared with those who did little or no exercise. Exercise seems to benefit the small arteries that control erections, much as exercise benefits other arteries, such as those that feed the heart. Thus, what happens to the penis may be an early warning of what could happen to the heart, such as a heart attack. Watching more than 20 hours of television each week, consumption of alcohol, smoking and being overweight were associated with higher levels of ED, as was having diabetes, previous stroke or taking antidepressants or beta-blockers. The risk factors for ED were about the same as those for heart disease. Therapy
In August 2003, the Food and Drug Administration has approved Levitra
(from the word levitate). Levitra
is a new drug made by Bayer and Glaxosmithkline that treats
erectile dysfunction in men. When taken prior to
sexual activity, Levitra helps a man achieve stronger and
longer lasting erections for sexual intercourse. It contains vardenafil HCl,
a drug in the same family as Viagra, for erection. Levitra comes with the
same warnings as Viagra. It should not be taken by men who already take
a nitrate-containing heart medication or alpha blocker drugs for high blood
pressure or enlarged prostate. Men who've recently had a heart attack or
stroke, men with very low or uncontrolled high blood pressure, and men with
the rare heart condition called QT prolongation also should not take Levitra.
The FDA suggests that all men undergo a physical exam before starting on
Levitra. The main side effects in healthy men were headache, flushing, a
stuffy nose and, rarely, dizziness. Additional oral medicines may soon be available to treat ED.
Cialis is being tested for safety and effectiveness. Cialis is a PDE5 inhibitor
developed for the treatment of erectile dysfunction. Cialis is already available
by prescription in approximately 40 countries worldwide
including Europe, Brazil, Australia, New Zealand, and Singapore.Cialis is
not yet approved for sale in the United States and is currently under review
by the U.S. Food and Drug Administration ("FDA"). Lilly ICOS continues to
expect a U.S. regulatory decision regarding Cialis late in 2003. Another drug being tested, Uprima, works on the brain and
nervous system to trigger an erection. Uprima is an Abbott Laboratories
product.
For more on the subject visit: http://kidney.niddk.nih.gov/kudiseases/pubs/impotence/index.htm Back to the Telangana Science Journal |
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(Lead the world from wrong path to the right path, from ignorance to knowledge, from mortality to immortality and peace!) One World One Family |
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