Question:
How much blood pressure is required for an erection? Never
seen numbers. I asume the blood pressure in the penis is no higher
than the blood pressure any other place in the body at the same time
the erection is occuring. It's simple hydraulics. It would seem to me
that he pump (heart) only pruduces so much pressure which is all thats
available to every organ in the body. Every extremity must share the
same blood supply. I think the penis is a strange animal because it
uses the same blood pressure to become pressurized unlike any other
body part.
Answer:
Yes, it is all about simple hydraulics. The penis gets hard for the
same reason you can use one hand to lift your car with a hydraulic
jack. The laws of hydraulics are the reason. When you operate the
handle on the jack, you're actually forcing a small piston to pump
fluid through a small opening into the area below a much larger
piston. The difference between the surface area of the small piston
and the large one multiplies, or amplifies, the force you apply to the
pump handle. Say, for ease of explanation, the surface area of the
small pump's piston is 1 sq. inch, and the surface area of the large
one, which actually lifts the car, is 10 sq. inches. (In reality the
difference between the two is many times greater) If you push down on
the pump handle hard enough to create a pressure of 50 pounds/sq inch
in the small pump (meaning you exert 50 pounds of pressure on the
small piston with its surface area of 1 sq inch) then that same 50psi
is exerted upwards on the large piston which is actually lifting the
car. It has a 10 sq inch surface area, so the 50psi exerts an upward
force of 10 x 50 or 500 pounds.
Here's how this analogy applies to your penis.
The penis is a unique organ among all those in your body. It has two
chambers, called the corpus cavernosa, which are a lot like sponges,
and through which most of the blood coming into your penis flows.
These two chambers are surrounded by muscles which are normally
contracted, keeping most of the blood squeezed out of the spongy
tissues. Picture, if you will, a sponge compressed inside a pipe.
Fluid can be forced through it and will come out the other end, but
the sponge can't expand due to the pipe surrounding it.
Now picture that the pipe is double-walled, and that all the fluid
going through the sponge and out the far end of the pipe is directed
to a rubber tube returning between the inner and outer walls of the
pipe.
Now here's where the hydraulics comes in. Compared to the diameter of
your blood vessels, the diameter of the penis is huge, with a surface
area of quite a few square inches. When you start to become aroused ,
the muscles surrounding the spongy corpus relax, much like removing
the inner pipe in our analogy. The blood continues to pour in and the
spongy tissue begins to expand. In reality your penis is a
multilayered organ, much like the double-walled pipe analogy. The
corpus cavernosa (the sponge) is surrounded by muscles,(the inner
pipe) which are in turn surrounded by a relatively inelastic layer of
tissue (the outer pipe). The blood enters from deep arteries into the
spongy tissue, runs pretty much the length of your penis, and returns
to the body through veins (the rubber tube) located between the
muscles surrounding the corpus and the inelastic outer layer. When the
muscles (called smooth muscles) relax and the corpus begins to expand
the veins returning the blood are squeezed between the smooth muscles
and the inelastic outer layer, shutting the veins off. Using the laws
of hydraulics, a relatively small amount of arterial pressure is
amplified by the large surface area of the penis resulting in a
diamond cutter erection assuming everything is working right. Blood's
coming in at full arterial pressure. It can't get out since the
return veins are squeezed shut. After relaxing completely initially to
allow a full erection, the smooth muscle goes into moderate
contraction as sexual excitement continues. Normally this has no
effect, since the high hydraulic pressure overcomes this contraction
and keeps the return veins shut down. If the veins are for some reason
only marginally shut off, though, this small contraction can be enough
to open up the exit flow resulting in premature loss of the erection.
To shut down the erection after ejaculation or cessation of
stimulation, the smooth muscles begin to contract more forcefully,
relieving pressure on and opening up the return veins, which reduces
the interior pressure allowing the smooth muscles to contract more,
which opens up the return veins more, etc. until your penis is again
flaccid.
Venous leakage takes place when the return veins are not squeezed shut
as they should be, either because of insufficient blood flow into the
penis, the smooth muscles don't relax sufficiently, or (and here I'm a
little fuzzy) the veins aren't flexible enough to squeeze shut
completely. You can lose a previously good erection if the smooth
muscles begin to contract forcefully prematurely due to tension or
worry ,like when her parents came home unexpectedly when you were
making out on the couch as a teenager, or when worry about keeping it
up creates the same kind of tension. If the smooth muscles hardly
relax at all, or the veins are incapable of being squeezed shut you'll
either never get an erection at all or you'll get a poor one. This
smooth muscle relaxation gets more iffy as we get older, which is why
erections get more chancy with advanced age.
The injections and the Muse suppository act directly on the smooth
muscle, causing it to relax. Thus you get an erection whether it's
warraned by sexual excitemen or not
Viagra, on the other hand, inhibits some of the action of the
chemical in the body responsible for causing the smooth muscle to
contract, allowing the erection to proceed more normally.
Restriction bands (cock rings) simulate the natural squeezing shut of
the return veins but don't cause smooth muscle relaxation (which is
why they work best if you can get an initial erection and later lose
it through leakage).
The pump bypasses the whole erection biological process by creating a
vacuum around the penis causing the pressure differential to overcome
the contracted smooth muscles and fill the penis with blood. After the
penis is full of blood, a restriction band traps the blood in the
penis and keeps it from returning to the body.
Now to return to the blood pressure question (thought I'd never get
there, didn't you?). Due to the hydraulic action of small arteries
feeding the relatively large penile surface area, I doubt a change in
blood pressure has a lot to do with the erection process. High blood
pressure through exertion or speeding up the heartbeat artificially
might or might not cause a marginally quicker erection, but the
firmness difference wouldn't be significant. High blood pressure
without either exertion or artificially stimulating the heart to beat
faster is usually the result of poor circulation, however, and a lack
of sufficient blood supply could certainly cause an erection problem,
especially if you also have venous leakage. Low pressure, on the other
hand, could be caused either by wide open arteries or a poorly working
pump (heart). If the former, the erection should be enhanced and
happen quicker. If he latter, who knows. We're getting a little
esoteric here.
Anyway, that's my take on the whole erection process (the mechanical
part, at least). I'm no doctor, so I may be talking crap. What I know
I got from reading on the subject, and I'm only as correct as what I
read, and can remember from it. Take it for what it's worth.
