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HOW
AN
ERECTION
HAPPENS
An erection is the
stiffening or hardening with enlargement of the penis that
periodically occurs upon a sexual and non-sexual stimulus. The
primary purpose of an erection is sexual intercourse.
The complex
erection mechanism can start in either the brain (a thought),
the penis (a touch), or the bladder (when filled). Upon
stimulation a beautifully intricate and balanced reaction of
nerve messages occurs between the brain and the reproductive
organs. The first thing to happen to the penis is a message is
received from the brain. This message causes nitric oxide to
be released from the tissue of the penis. Nitric oxide in turn
causes the same cells of the penis to produce cyclic guaosine
monophosphate (cGMP). This chemical, cGMP, has the ability to
cause rapid relaxation of both the arteries of the penis and
the smooth muscles that line the network of small
interconnected spaces of the corpora cavernosa and corpus
spongiosum. This relaxation response has an expansive and
enlarging effect on the penis, because it causes more blood to
flow into the penis and it is “loosened up” to receive and
hold the extra blood that is being shunted to it .
Going up.
Blood quickly enters the network of erectile tissue spaces as
this relaxation continues along the length of the penis. A small
amount of blood enters the corpus spongiosum, but the majority
of it engorges the corpora cavernosa which expand to hold 90%
of the blood involved in an erection.
As more and more
blood enters the relaxed spaces of the penis, the expanding
spongy tissue presses against the firm tubular connective
tissue sleeves known as the tunica albuginea and Buck’s
fascia. This increased pressure in turn pushes against veins
that normally let blood out of the cavernous and spongy spaces
of the penis, compressing and closing their valves. Now with
the veins closed off a greater and greater amount of blood is
trapped in the penis. When the three penile chambers are
filled with blood the penis is at its maximum length, diameter
and rigidity, and is said to be erect.
The glans or head
of the penis, the mushroom-like end of the corpus spongiosum
that sits like a cap on the end of the penis, remains more
soft and pliable during erection because its tunica albuginea
is much thinner than elsewhere in the penis. This thinness of
the tunica at the head of the penis does not allow it to
develop the rigidity that other parts of the penis achieve. Of
course this is a good design feature, since the relative softness of
the glans protects the cervix of the uterus during
intercourse.
Going down.
After ejaculation, or upon loss of mental or physical
stimulus, the brain stops sending signals to the penis to
release nitrous oxide. With loss of the nerve signal and
subsequent chemical release, the flow of blood is reduced, the
pressure drops, the vein valves are no longer held closed and
so open up to release blood, and the erection ceases. The
penis returns to its normal pre-erectile size and flaccidity.
A simple
balloon can give you a better idea of how an erection
works: Before you blow up the balloon, the balloon wall
material is very soft and flexible. Put a little air into the
balloon and it begins to change shape by filling, making the
balloon larger. As more and more air gets trapped inside the
closed space of the balloon, it continues to become more rigid
and large, until a limit is reached. After this certain limit
point the previously flexible balloon material gets
surprisingly tight and rigid. To keep it rigid you tie off the
opening, and to reduce the rigidity you untie the opening.
PD causes a
problem with the erection mechanism because the vein
valves “leak” and cannot build up sufficient pressure to
create a full erection, due to interference from the scar tissue in the
tunica albuginea. Its as thought the scar tissue blocks the
closer of the vein valves, just as a kink in a car door
keeps the door from closing completely, or not at all.
As improvement occurs in the size, shape and density of the
PD scar as a result of successful therapy, one of the first
observable changes will be in the quality of erection
response.
And this is why we contend, as you
will read in
other parts of this website, PD is all about the scar.
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