Girth theory: Pumping vs. clamping

A hole in the can would equalize the pressure immediately, wouldn’t it?

Yes, so would a rupture in the tunica.

LOL

I don’t understand your point.

If you remove water from a can, air rushes into the can to fill the space taken by the water. If you pump water out of the can without letting air in to replace it, the can will collapse. In essence, you are pulling a vacuum on the can by removing the water.

Real life example:

I worked in a Chemical plant where we unloaded tankers trucks or rail cars full of liquids. These tankers have a little 1” vent line on the top of the tank which you must open before you start pumping the liquid out.

I saw first hand, a 20,000 gallon tank collapse like a beer can because the operator started pumping liquid out and forgot to open the vent. Good way to lose your job.

Exactly.

That is an open system though, and in your example an active pressure differential is being created by pulling a vacuum.

With a penis pump, the system isn’t quite the same as there is no “open” part of the equation. You are pulling a vacuum, but there internal tissues are not being replaced with air.

Smart ass.

You propose that there is a normal venous link in the penis at peak erection. This is true in the spongiosum, as this is critical to allow it to stay soft enough to allow ejaculation. Venous leak is something we all hope we don’t have. At peak erection, venous outflow and arterial in flow are near zero.

Here are 2 quotes regarding erection and blood flow.

I have a great graph from a monkey where nerves were stimulated to cause erection. It shows the pressure in the cavernosa and the blood flow into the penis in the different stages of erection. I hope that you will allow me to show this picture.

Thank you, I resemble that. :)

The pressure inside the penis is being maintained by the circulatory system controls outside the penis, (blood pressure generated by the heart, vasoconstriction etc) so I would say it is an open system.

You are right that gas or liquid inside a closed balloon behave differently. If you pull a vacuum on a gas filled sealed balloon, the balloon will grow as external pressure becomes smaller relative to internal pressure. The gas expands along with the balloon, and the pressure inside the balloon will drop as the gas expands. (Paradoxically the balloon is bigger but the pressure inside it is less).

With a liquid filled balloon, if you pull a vacuum around the balloon it will not expand because the liquid won’t expand.

But the penis is different. Pulling a vacuum around the penis causes the penis to expand due to the pressure differential, because you have a pump (your heart) providing the a constant pressure and sufficient liquid to accommodate the expansion.

Interesting.

The flow, for most of the graph is very low, but not zero. That is basically the example I gave of the garden hose with the pin prick in it. Also remember it is just one artery.

I have not researched the hemodynamics of normal erections, but I figure there is probably some low flow of blood through the penis during erection in order to prevent ischemic damage. Figure some guys on this forum say they have continuous sex for 1,2, 3 or more hours. With zero replacement of erectile blood, I imagine that oxygen deprivation in the penis would make this kind of marathon sex very damaging.

Agree.

I spent the first years of bodybuilding over training. I know there is a minimum to maintain and a minimum for growth. I, for a long time, came close to maximum and it did not provide any growth. It is much more interesting to know minimums for maintenance and growth rather than the limits - at least now that I am older.

Mravg and Pudendum,

I think the other thing that is not taken in to account is the pliability changes in the tunica. Under stress and time, it does change and allows for greater expansion. This may also explain why low level pumping works.

That is true in an open system where air is necessary to replace fluid volume and I agree. I’ve seen similar collapses and I agree with you on this one.

I just have a question. What’s this got to do with the erection chambers?

The erection chambers fill due to changes in arterial pressure in, smooth muscle relaxation in the walls of the blood spaces in the erectile chambers (venous sinusoids) and closing down the blood flow out in the veins draining the penis. To empty the veins open up and the smooth muscle in the cavernosa contract forcing blood out. There is no open system here. Air does not replace fluid.

When I was commenting on you aluminum cam system (sealed completely), I was suggesting replacing the air in the can with fluid at 200 mm Hg, not emptying or filling the can. I was talking about exposing it to the pressures you use when you pump.

I think we’re talking about entirely different things.

Open system is a relative term. The penis is complex. You will agree that it does not exchange for air or any other gas. It also has very specialized physiologic mechanisms to empty and fill. I think we agree. In the sense of the open systems you described, the penis is not an open system.

This is particularly true at peak erection where blood flow in and out of the penis falls to near zero (see graph attachment in my prior post).

I am not sure how you can say there is a difference between a filled balloon and the penis as far as response to negative pressure at peak erection (I will grant you that up to this point, blood is drawn into the penis by the negative pressure; this is what made it good for guys with ED). You don’t think there is a distending pressure of the fluid in the balloon. For our balloon example lets make the balloon a thicker latex (like old condoms), this makes it more resistant to rupture. The effect of the negative pressure will depend on the factors of wall flexibility or distensibility.

Again at peak erection, the penis is exactly like the balloon, an isolated system, Therefore the effects depend on compliance, not inflow or outflow. Remember, I’m talking about peak erection.

How much blood do you think it takes to fill the penis? Second, this is a monkey penis that is smaller in volume that a human penis. There is no reason not to believe that blood flow will be relatively higher in the arteries filling the erectile chambers in us, a larger higher order primates.

Blood flow at peak erection is essentially zero:

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and

The tissues of the penis can withstand a low oxygen environment for some time. It is only after extended periods of sustained peak erections that low oxygen in the tissues (ischemia) is a problem; one of the problems in priapism.

By the way, it’s interesting that this reference uses the term Skeletal Erection Phase. Is this why we call it a boner?