I’ve put together this little experiment to examine the way which a different number of tunica layers might effect PE and some possible effects this physiological difference might have on the function of the penis when becoming erect and stretched.
I’ve used balloons and air to simulate the tunica albuginea penis and its expansion and stretch. This definitely is NOT a well put together empirical study, just a model and should be viewed as such. So these are some shortcomings in my model:
First off, I have used air from my lungs (a compressible gas) to simulate the inflow of blood (an non-compressible liquid) into the cavernous tissue chambers of the penis creating pressure within the tunica. Water would have been a better medium.
I pushed on the balloons in the expansion study to gauge pressure, looking for a similar degree of hardness (like when you kick your tires to check their pressure) - this could have been much more exact if I would have used a pump with an inline pressure gauge to fill the balloons.
In the stretch test I also went by feel. I stretched the balloons until the elastic threshold was reached, I would best explain this as the point which the stretch stops feeling like stretching rubber (returns to its original size) and begins to feel like stretching plastic wrap/cellophane (does not return to its original size). You can definitely feel this point, but it introduces more human error into things.
Last, I have used rubber, a substance with an irregular fiber alignment that is very elastic with no fluid-based viscoelastic properties, to simulate a collagen matrix, a substance with a hierarchical fiber alignment that is both elastic and viscoelastic in nature. Not sure what I could have used instead, I was all out of human tunicae. ;)
I’m sure this analysis has many other shortcomings, but my point is that this is a model, not any kind of empirical observation.
Tunica Albuginea layers:
The tunica albuginea penis can have one, two, or three layers. The normal structure is bi-layered, but research shows this isn’t always the case. I have seen two studies that illustrate this phenomenon, but I have been limited to Google on my research today and yesterday as I didn’t have access to the databases at the library of the college I work at, so I have just one I found online to cite. Here is the citation and my summary:
Histologic study of the tunica albuginea of the penis and mode of cavernosus muscles’ insertion into it. Shafik A, et al. Arch Androl. 2006 Jan-Feb; 52(1): 1-8
To BRIEFLY summarize the researchers looked at several cadaver penises and found that in some cases the structure of the tunica albuginea can differ from the typical bi-layer structure found in most penises. The researchers found that in 7.14% of the subjects they examined, the tunica was composed of a single layer of connective tissue with the fibers aligned longitudinally. In 71.43% of the subjects the tunica followed the typical bi-layered structure with an inner layer with circular fiber alignment and an outer layer with longitudinal fiber alignment. In 21.43% of the subjects the tunica was composed of three layers with an inner and outer layer possessing circularly aligned fibers sandwiching a middle layer with longitudinally aligned fibers.
Due to the setup of the standard tunica, I believe we can make some predictions as to how a tunica with a non-standard setup will function regarding PE and the way in which erections happen.
First, the typical bi-layer structure is composed of an inner layer of circularly aligned fibers and an outer layer of longitudinally aligned fibers. Connective tissue only stretches well elastically in the direction of the collagen fibers. What this means is that the inner layer can expand elastically outward, but the outer layer cannot do so nearly as well. This means the outer layer acts like a rigid tube when the inner layer expands laterally and pushes against it, like a tube and tire. The outer layer resisting the inner layer creates a hard erection. Without the inner layer, a single layer tunica will expand very well length-wise, but will need a much greater inflow of blood to achieve the same degree of internal pressure and, therefore, erectile hardness.
Second, just an increased number of layers will make the tunica thicker and tougher. This would mean less expansion during an erection at similar levels of stimulation but a much faster build-up of pressure and, therefore, hardness. Also, a thicker tunica (more layers) should be more difficult to stretch at a constant level of force. The fully stretched length, however, would not be dramatically different as all the layers possess the same fully stretched elastic length, but the tunica with more layers would require more force to achieve a fully stretched length.
I am primarily testing the second predictions here as I do not have any materials that are elastic but with a hierarchical fiber alignment so I have no means of orienting the fibers in the proper way.
The expansion test:
Picture 1 - smallest balloon is three balloons inside one another. Middle balloon is two. Biggest balloons is a single balloon.
This shows that a thicker tunica requires a much lower volume of filler (air in this case) to achieve the same degree of hardness.
The fully stretched test:
Picture 2 - a single balloon fully stretched
Picture 3 - a double balloon fully stretched
Picture 4 - a triple balloon fully stretched
They all stretched to approximately the same length, but the double balloon was hard to stretch that far, and the triple balloon was nearly impossible. Also, they stretched longer than the ruler, sorry.
The force vs. stretch test:
Picture 5 - a single balloon attached to 2.5 pounds of weight
Picture 6 - a double balloon attached to 2.5 pounds of weight
Picture 7 - a triple balloon attached to 2.5 pounds of weight
Sure enough, the more layers the less elongation at a constant level of force.
So, I think this illustrates my predictions, probably doesn’t prove anything.