Male Plumbing 101:

Understanding Erections and What Can Go Wrong



David Sebringsil


One way of visualizing the male penis is as an elastic pipe or tube, with a valve on each end.  Normally, the valves are open, allowing water to flow freely in and out of the tube, and the elastic pipe will not get bigger. However, if the valve allowing water to flow out of the pipe is restricted, and the valve allowing water to flow into the pipe is open, more water will flow in than flows out. Since the pipe is elastic, it will become larger, until the valve allowing water to flow out is re-opened so that water can again flow out at the same rate it is flowing in.


Ordinarily, the same amount of blood flows in as out of the penis, and the penis does not become erect. However, during an erection, the male penis fills with blood, and it becomes bigger. The valve permitting blood to flow back out of the penis constricts to a degree, and the penis becomes erect. More blood is flowing into the penis than is able to flow out. Clearly, a key element of the erection is the ability to restrict blood from exiting the penis as fast as it is entering.


Initial Arousal


We are quickly getting ahead of our story, however. Let’s start at the beginning. As I have indicated in other writing, for both men and women sexual arousal is centered in a certain part of the brain, which I have dubbed “arousal central”. What an individual finds to be sexually arousing—or not—is frequently as personal as a fingerprint. In the media, these are dubbed as sexual “turn-ons” and “turn-offs” . Some sexual turn-ons are widely accepted as by society as “normal” and ok. Other sexual turn-ons might be regarded as “normal” but not ok from the perspective of some people but not others. An example here might be a pornographic magazine or video. Still other sexual turn-ons might be regarded as harmless but considered at least by some to not be normal. Most fetishes involving inanimate objects such as articles of clothing fall in this category, and tend to be embarrassing if not just silly if revealed to others who do not share the fetish. At the same time, college guys who engage in “panty raids in women’s dormitories would perhaps be regarded with amusement but ordinarily not be thought of as anything other than normal. The final category consists of turn-ons that are considered harmful and illegal in society, and these turn-ons generally involve sex crimes such as rape, pedophilia, and even sex-related murder.


However, the vast majority of sexual turn-ons are regarded by society if not completely normal at least OK and harmless if not amusing. The entire debate over gay/lesbian rights is centered on the idea that there are those in society who for whatever reason believe that sexual turn-ons involving the same sex somehow cannot be considered normal or ok. Fortunately each year progress is made as a declining share of the population takes on this viewpoint.    


So let’s assume that a guy is turned on sexually for some reason. Somehow and for some reason, “arousal central” has been stimulated. The particular kind of stimulation is not important: what is important is that it works for the guy and the guy is in the initial stages of feeling aroused.


What happens next? Well the answer most men might give is that as a consequence, the penis starts to fill with blood. But this is not quite accurate.  The man can be aroused without any initial response from the penis. Indeed, arousal central in the brain does have a secure wire connection to body parts in the groin area, but the initial nerve signals are sent not to the penis, but to two glands, primarily the Cowpers gland, but to a certain degree the prostate.


The Cowpers in particular goes into secretes a perfectly clear, slippery, viscous fluid which is referred to in slang as “pre-cum” but technically the better term is “pre-ejaculate.” For a long time biologists tended to believe that this fluid was almost exclusively by the Cowpers and not the prostate gland, but the current view suggests that fluid from the Cowpers is mixed with some fluids from the prostate, even initially.


From a chemistry and biology perspective, pre-cum is really interesting stuff. Other male mammals such as bulls also produce pre-cum in the initial stages of arousal so pre-cum must serve some biological function. The slipperiness of the fluid is due to the same chemistry that makes soap slippery. Soap gets its slipperiness from its high pH associated with Hydroxide ions present in the lye (aka NaOH or sodium Hydroxide) used in the soap making process.


Why would pre-cum also be high in Hydroxide ions? Well, one explanation is that the vagina tends ordinarily to be acid, that is, low pH. But we know that a low pH can be very toxic to sperm in semen. So one theory says that one biological function is to neutralize the acid by raising the pH vagina in which the sperm swim. This explanation as to why pre-cum exists in mammals including humans is by no means universally accepted among biologists.


A simpler explanation is that it is simply a good lubricant for intercourse—even better than commercial KY gel in the bottle. From a slipperiness perspective the stuff is pretty amazing. Perhaps both explanations have some merit to them.


For many, if not most guys, the initial stages of arousal are generally accompanied by some viscous drops of pre-cum. A man might not even realize he is becoming aroused until he feels a wet spot forming at the very tip of his penis, or starts to observe drops of pre-cum. This can continue for a sustained period without an erection, or not.


Over the years, a few guys have written to me to complain that they never have or can’t “pre-cum”, and are concerned that this might somehow be abnormal or perhaps a medical problem. While I don’t doubt what these guys are telling me, and this perhaps is true for a few guys, I remain convinced that most guys who claim that they never pre-cum are moving from the initial arousal stage to a full-scale erection very quickly. I suspect if they could somehow slow the process of moving into an erection, most of these guys would pre-cum as well. An interesting medical question is whether or not guys who are regarded as impotent from a medical perspective can still pre-cum.


As the erection moves past the very initial stages, pre-cum almost invariably stops entirely. The other external indicator is once the penis starts to fill with blood the opening of the penis goes from circular to slit-like. Once this change in shape has occurred, pre-cum almost invariably ceases and the tip of the penis will be completely dry until semen begins to flow. 


For both men and women, it is generally recognized that the level of testosterone or compounds closely related to testosterone largely determines the level of libido, which we can define as initial interest in becoming sexually aroused. Ordinarily, in both men and women, the normal level of testosterone tends to slowly but persistently decline. There has been some interesting research going on regarding the usefulness of testosterone supplements as a possible mechanism for reversing components of the aging process, in particular the decline in bone density in women and as a means of reducing the incidence of impotency in men. Unfortunately, the very recent research does not support the contention that testosterone supplements could be a magic bullet in reducing the effects of aging. In the most recent study, the only significant effect of the testosterone apparently was a slight increase in libido for older females! Researchers did not find that the older guys in the study were able to get aroused or sustain an erection with the testosterone treatments than without.


The Erection Phase


Once we get past the initial arousal phase, which consists primarily of arousal central in the brain sending signals to the Cowpers gland and to a lesser degree, the prostate, the next step involves the initial stages of the erection. If an erection is to take place, more blood must flow into the penis than exits. Ordinarily the blood flowing out of the penis stays more or less equal to blood flowing in, and no erection occurs.  So, for an erection to take place, arousal central must constrict valves that ordinarily would carry blood out of the penis, while maintaining and perhaps increasing blood flow into the penis (during sexual arousal, blood pressure rises as the heart beats faster! It’s nothing short of amazing how this works. The increase in the amount of blood flow going into the penis along with the restriction in blood flow out is what causes the erection to occur.


Obviously this works better for some guys than others. Young guys in particular would tend to easily constrict valves that control the outward flow of blood very well, and the penis quickly rises and salutes. As guys get older the valves controlling blood outflow tend to not as fully constrict, and as a consequence erections may take considerably longer, regardless of the arousal level. Young guys often can get a full erection and even have an orgasm without any manual stimulation at all. As men age they tend to lose this ability.


Also, consider that the penis contains many very tiny blood vessels. Any lifestyle   that would cause small blood vessels to partially clog will tend to make it more difficult to get and sustain an erection. Smoking, for example, has been linked to the accumulation of grunge in these tiny blood vessels and has been identified as a possible factor. Being overweight and/or eating a diet high in fats may do the same thing. 


Current research that links the role of a particularly bad class of fats called trans fats is of particular interest. Most of the recent research is primarily concerned with the role of trans fats as being a contributory factor in circulatory problems of various sorts as well as heart disease and stokes. The medical evidence that trans fats should be reduced if not eliminated from diets from a health perspective is accumulating.


Trans fats include a lot of vegetable fats that are solid (not liquid) at room temperature. Solid vegetable shortening would likely be high in trans-fats, but most liquid cooking oils are trans fat free. Trans fats still appear in many commercial products including sandwich cookies (the fillings are a mixture of solid vegetable fat and sugar) and French fries from fast food places. However, most potato chips, crackers etc are now trans fat free.


The accumulating medical evidence for avoiding trans fats as a method for keeping blood vessels free of fatty deposits is mostly fairly recent, and many men have had a lifetime of diets high in fats, both plant and animal, that are solids at room temperature. While the research might not yet be there, it seems only logical that reducing the intake of any fat solid at room temperature with a particular focus on attempting to eliminate trans fats entirely from the diet could yield hearth benefit for the circulatory system throughout the body. A comparatively simple dietary restriction could not only reduce the risk of heart attack and stroke, but also improve the functioning of all those tiny blood vessels in the penis, making erections both easier to get and maintain, but harder. To me, this seems to be a very reasonable tradeoff.


Pills such as Viagra and Cialis


What do drugs such as these do, and what do they NOT do to improve sexual function? First of all, neither of these drugs was designed to deal with problems related to a lack of libido, that is, interest in sex. The only possible link here might be that if a man knows he can get and sustain an erection without difficulty by using a pill prior to sex, he may become more interested in attempting to have sex.


All the pills in this class work to dilate blood vessels in the penis, so blood can flow in more freely and better engorge the penis. So if part of the inability to sustain an erection is due to the fact that tiny blood vessels within the penis have become partially clogged and therefore do not fill with blood as they should, the drug may help.


At the same time there are other ways of increasing blood flow in the penis that might be successful as well. These include general weight reduction for overweight individuals lowering or eliminating solid fats from the diet, especially trans fats increased exercise and quitting smoking. The drugs may be this viewed as simply one of a series of possible steps a man might take in an effort to improve sexual function. Some men have reported great results with one of the drugs, whereas others have been less enthusiastic about their usefulness and potential.


Exercise and Male Libido


I have become increasingly interested in the role that vigorous exercise, aerobic and non-aerobic, might play in male libido. Obviously, any vigorous aerobic exercise is going to yield many benefits to the entire circulatory system, likely including the penis, so guys who regularly engage in vigorous aerobic exercise are likely to be more sexually fit as well, other things being equal.


For a long time, biologists have known that testosterone or compounds closely related to testosterone is responsible for libido in both males and females.  This is despite the fact that testosterone is regarded as the “male” hormone, essentially the biological counterpart to estrogen in females. This simple-minded view basically ignores what actually goes on in reality. If you studied biology in the 1950s, the textbooks would say that testosterone is manufactured exclusively in the sex organs or gonads, but perhaps under the control of the pituitary gland. Testosterone was clearly linked to the development of secondary sex characteristics in males that appear at puberty. These male secondary sex characteristics include pubic hair, facial hair, the appearance of the male “Adam’s apple”, the lowering of the male voice at puberty (boy sopranos suddenly are singing tenor if not baritone or bass), and even muscular development. These secondary sex characteristics are linked to an increase in testosterone levels at puberty, thought to be primarily due to a biological clock in the pituitary gland.


If women are given extra testosterone, they will tend to develop secondary sex characteristics normally associated with post-pubescent males. But a small amount of testosterone normally present in females bears the primary biological responsibility responsible for the female sex drive.


The current view on testosterone is that it is normally made in the body in places very different from the gonads. In general, athletes will tend to run higher normal testosterone levels than non-athletes, other things equal. The recent controversy surrounding the Tour de France winner and what should be considered a “normal” testosterone level versus a level clearly augmented with drugs highlights the issue.


We also know that many female athletes who train a lot frequently start to acquire secondary sex characteristics of the male. They may no longer have monthly periods, for example, and breasts may be come smaller as fat is converted into muscle. We would normally associate many of these changes as attributable to higher testosterone levels as a consequence of intensive exercise.


Generally, it is easier for men to build muscle than it is for females, and this is believed to be linked to the presence of larger amounts of testosterone, chemical compounds closely related to testosterone, or perhaps other less well-studied hormones normally present in larger amounts than in males than in females. Only fairly recently has it become increasingly apparent that exercised muscles themselves can be factories for hormone production, and that this production is occurring at sites very different from the sex organs.


But we can’t really talk about what one body part (say a muscle being exercised) is doing independent of other body parts (say the gonads) . Obviously there has to be a control center for all of this or testosterone levels would skyrocket completely out of control. The basic biology is that the pituitary is the basic regulator, but that other glands may be involved as well.


This is all interesting, but what does it have to do with male sexuality? Well, simply put, it could very well be that various forms of exercise could be a key to maintaining and even improving male libido as men grow older in part because of an increasingly clear linkage between exercise and testosterone production.


We have already discussed the possible usefulness of aerobic exercise in improving cardiovascular health in general, with the idea that if cardiovascular health in general is improved, there may be positive benefits with respect to being able to get and sustain an erection. I suspect also that runners, bicyclers and others who go in for sustained aerobic exercise in its various forms than does the population that does not participate in these exercises regularly. 


Exercises focusing on muscle building, however, tend to be non-aerobic, and thought to have less impact on cardiovascular fitness than aerobic exercises (This contention has been the subject of debate, and the argument that non-aerobic exercises such as weight lifting do nothing to improve cardiovascular fitness is by no means universally accepted. However, if muscles exercised in non-aerobic exercises such as weight lifting do become testosterone-generating factories, then such exercise may become a critical step in maintaining and perhaps even increasing male libido during the normal aging process.


Recent research conducted in nursing homes has suggested that if nursing home residents pursue even a moderate amount of weight training using light weights, their overall health often can be dramatically improved. We wouldn’t ordinarily expect weight training to be of use for nursing home patients!


Lately I have been observing what I believe to be a linkage between exercises designed to tome and increase the size of muscles in the upper body and chest and libido. I work out about a half hour each day on a rowing machine and supplement that with some weightlifting. I have found what appears to be a linkage between the amount of effort I expend weightlifting and my libido level.


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