Pardon my delay in responding, been a little busy.
Originally Posted by mravg
Pudendum, I appreciate your knowledge of erectile physiology. I don’t pretend to know that much about it and don’t intend to question what you say. You provide good references. Blood flow in the penis during erection is apparently very low, or zero, but there is a big difference between zero, as stated in your first reference, and almost zero, as stated in your second.
Sure the penis can withstand low oxygen for “some time” but how much time is that? How much flow is almost no flow? I would guess that even very miniscule flow through the penis during marathon sex can do a lot to prevent oxygen deprivation.
Well, you answer your own question in your next sentence.
There you go. That doesn’t happen with the balloon. Actually it is more accurate to say that blood is forced into the penis by the heart, facilitated by less external pressure on the tissue, allowing it to expand.
It appears that you and others have not read my statement in an earlier post in this thread in response to Mr. Happy:
Originally Posted by pudendum
Understand that I picked a very discrete point in the erection; max. The penis is not a simple system. You add the real issues of tunica compliance the decreases as the erection approaches max. You are not placing a direct inward force on the penis when you pump, you are in fact doing the opposite. This is why the clamp should have a greater effect at PEAK erection.
Again, I have no doubts that pumping works at lower levels of erection and I do not dispute success. But to get an understanding of a complex organ like the penis which to say the least undergoes dynamic changes experienced nowhere else in the body, you must break things down into discrete subsystems and/or situations. I picked peak erection to try to get some handle on that specific phase.
It is important to understand my posts in light of this. In my opinion, the dynamics of the penis at any other time (except when flaccid) is very complex and until we understand the penis at very specific times in erection, we’ll have no basis for comparison.
If you chose to disbelieve the experts, who know a lot more than you and I do regarding the blood flow and pressures in the tunica at peak (or skeletal) phase of erection, that’s ok. They’ve done the experiments, had their work reviewed by other experts and then get it published in respected medical journals and textbooks. I haven’t. I tend to believe what when they say.
Tom Lue, MD is a respected expert in erectile dysfunction and Pyronie’s disease. He is a Professor, vice-chairman and occupies an endowed chair in the Department of Urology at the University of California San Francisco School of Medicine. When he says that blood flow entering and leaving the cavernosa ceases at the peak erection, I believe him. What you believe is up to you.
Originally Posted by mravg
Look at it this way: you connect a hose with 60 psi water pressure to a metal tank. there is a pipe on top of the tank with a valve on it. You fill the tank until water is coming out of the pipe, then shut the valve.
The water is still turned on, so there is 60 psi in the tank and hose, but there is no flow in or out.
Now, you magically turn the tank into a rubber walled tank that expands 5% due to the 60 pounds of pressure on it.
The tank has grown in size, water flowed to fill the additional space, then stopped when the system reached equilibrium. The pressure in the tank is still 60 pounds.
That is your penis.
No, that is not your penis at peak erection. Why not? Because the contraction on the cavernosa by the Ishiocavernosus muscles raise the pressure in the penis much higher that the inlet pressure, unlike in your example where tank pressure and inlet pressure are the same (ignoring where the inlet hose is attached). In the penis the cavernosa pressure is 200 - 300 mm Hg and inlet pressure is about 120 mm Hg.
Originally Posted by mravg
Put a giant cylinder over this tank and pull a vacuum. The tank will grow more, water will flow into it, it will reach equilibrium, and the pressure will still be at 60 pounds.
This is not the situation in the peak erect penis. The pressure in the cavernosa probably does drop to some small degree but never low enough to allow new blood into the penis AT peak erection. The movement of blood from the unpumped internal portions of the penis probably move into the pumped penis to cause a small but finite increase in volume-induced wall tension.
Originally Posted by mravg
The balloon full of water is much different:
Take the same example of the full tank.
This time you shut off the hose first with a valve at the tank where the hose connects to the tank. ( a knot in your balloon!)
Then you magically turn the walls in to rubber as before.
The tank grows due to the internal pressure, and as the tank grows, the pressure drops. It reaches equilibrium at some size smaller than the tank in example one, and the pressure is something less than the original 60 pounds.
Now put a giant cylinder over this tank and pull a vacuum. The tank will not grow more as in the first example.
The difference is the pump. The heart in your body, or the pump at your city water department. The balloon is a closed system, and the penis is not, because it is connected to your heart, even if there is no flow, there is pressure applied from the outside, just like that hose connected to the full and closed, tank.
If the vessel pressure is much higher than inlet pressure (blood pressure) than the effect of inlet pressure can be ignored. There have in fact been suggestions that maybe blood flow backwards in arteries because the cavernosa pressure is so high, but this has never been observed. If in your situation the tank pressure was double the 60 psi inlet pressure, flow would probably flow out UNLESS you close the system, like the penis at max erection..
I also notice that you have disregarded my explanation of the energies exerted on your original pipe and on the balloon (and I’ll grant that the change in volume with the change in pressure of a liquid is small) with a negative pressure. It is important to understand the effects of vessel was compliance on whether the applied force (or negative pressure in the case of pumping) is converted to kinetic energy and allows for expansion or whether the wall is so poorly compliant that the effect is only potential.
The tunica is more like the pipe than the balloon, with regards to the wall.