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Weight/Math Question - ???


Weight/Math Question - ???

OK all you engineers out there help me out with this one. I found an article that gives the tensile strength of the tunica (how much force it can stand before deforming.) I want to translate this into weight. Here is a copy of the article:

The elasticity and the tensile strength of tunica albuginea of the corpora cavernosa. - Bitsch M - J Urol - 01-MAR-1990; 143(3): 642-5 (From NIH/NLM MEDLINE)


The aim of this study was to determine the tensile strength and the elasticity of the tunica albuginea (TA), and describe morphological structures in the tissue before and after mechanical deformities. Twenty cadavers of men aged between 33 and 83 were examined. Cavernosometry was performed in all specimens. Afterwards in five cadavers the flow rate was increased until a herniation of the TA appeared. A strength about 1500 mm. Hg was found. Similar results were found in four who had an inflatable prosthesis (AMS 700) inserted, and the intraprosthetic pressure increased until a deformity was noted. Slices of TA (thickness 1.3 to 3.3 mm.) from 11 specimens were tested in a tensiometer. The elasticity coefficient was found to be around 10(8) N/m2, and the tensile strength to be 600 to 750 mm. Hg (10(4) to 10(5) N/m2). The difference between the tensile strength achieved in the tensiometer and during saline infusion is possibly caused by the intracavernous framework. Microscopy showed that TA is mainly composed of collagen fibres which are situated in an undulating arrangement, with a few elastic fibres arranged longitudinally which connect the undulating bundles of collagen fibres. When the tissue is overstretched, the elastic fibres are destroyed and the undulating arrangement disappears.


The elasticity and the tensile strength of tunica albuginea of the corpora cavernosa.
Bitsch M - J Urol - 01-MAR-1990; 143(3): 642-5

Notice the tissue strength is listed in mm/hg and N (newtons.) Anybody know how to convert this into pounds? I found several online conversion sites but I’m not sure I’m doing it right.

For 1500 mm/hg - I got 28.5 lbs/sq inch.
For 700 mm/hg (average of 600-700) - I got 12.35 lbs/sq inch.

Even if this is correct, what would this translate in to say hanging pounds?

Thanks for your help!


Let me tell you the secret that has led me to my goal: my strength lies solely in my tenacity.

Louis Pasteur

9.8 Newtons = 1 kg. 1 kg = 2.2 lbs. So 1 Newton of force is equal to 0.22 lbs of force.
51.7 mmHg (millimeters mercury pressure) = 1 psi
1 psi = 6893 N/meters squared

I attempted to get the original manuscript from my medical library electronic resource, but unfortunately their subscription starts in 1995. An abstract is a very sparse presentation of data and has a very limited description of methods; in this case particularly regarding the harvesting of the TA from their “volunteers.” Thunder is right. The donors were dead. TA is a living tissue, not just a plain fibroelastic layer. When tissue dies, its compliance changes. It generally decreases; that is it gets stiffer. With all this in mind I will tell you what I think. Be aware that their interest is in cavernosa compliance with expansion, not stretch (which are probably different).

Their microscopic description is indiscernible with out micrographs and a better description (which you will find in the body of the paper).

In five of their 20 cavernosa, they found a burst pressure of 1500 mmHg, or as you converted, ~ 29 psi. That’s just about the pressure of your typical auto tire. Their test of tensile strength and elasticity coefficient were performed in tissue slices, but again it is difficult to tell how they were obtained. Were they longitudinal or cross-sectional? Did they strip the surrounding tissue? Was their goal in testing TA coefficient of elasticity and tensile strength to determine potential cavernosa expansion or longitudinal stretch? I would believe the former for this reason. Most urologists don’t give a tinker’s damn about PE at least with regards to lengthening. They are concerned with penile turgidity only; basically can you get enough hardness for insertion (that’s why they discussed inflatable prostheses here). So their data on both tensile strength and coefficient of elasticity are for circumferential expansion and not longitudinal stretch. Therefore their data probably have little relationship with longitudinal stretch.

If you could obtain the complete manuscript, you would probably get answers that might help you more. Best of luck.

It seem that main purpose of article’ Docs were to know the force needed to achieve an erection, not a permanent enlargement.

However, if we could find that the weight needed to elongate the tunica of a dead man is, for say, 2kg / cm*cm, was this useful?

In thinking more about the limited data presented in this abstract, whether they were looking at circumferential or longitudinal tensile strength and coefficient of elasticity (ratio of the applied stress to the change in shape of an elastic body), the tunica albuginea of the penis is an amazingly tough and stiff investing layer. It’s probably not surprising considering its function in limiting the expansion of the corpus cavernosa so that blood engorgement creates a hardened penis to increase the population. One could surmise on a natural selection/survival of the fittest basis, a stronger, less deforming, greater tensile strength tunica has a an evolutionary benefit. Even so these numbers are very impressive, though they are not directly applicable to us on a practical basis regarding tunica stretching

Yes you converted properly. However there is something to be said about the way they conducted this experiment. How many of us have inserted (presumably in the urethra, correct me if I’m wrong) an inflatable prosthesis and than continuously expand until deformation is reached? That pressure would be dispersed over an even number amount of matter, making the force much more comfortable. Hanging however uses less of this energy displacement and could cause problems. For example, who started hanging at 12.35 lbs.? Not many I bet, this seems much to intense. And I’m sure most don’t get to 28.5 lbs, that seems like a lot to. These results don’t mean much to the average LIVING man.

Pudendum summed up the science of it extremely well. Don’t go off these results, they don’t mean much for us.

The inflatable prostheses they are talking about are surgically implanted in individuals with primary or complete secondary impotence untreatable by medications. The Scott’s inflatable prosthesis is the Cadillac of penile prosthesis (as opposed to a fixed prosthesis). Inflatable chambers are placed inside the TA after the veonus sinuses of the corpus cavernosa are obliterated. These chambers are plumbed to a resevoir (generally placed in the abdomen) and a pump (generally placed in the scrotum) which fill them when you want to be erect and drain them when you don’t. Don’t run out and get one because they usually put in chmbers that are about 2/3 your normal erect size (so that your ‘flaccid’ chamber filled penis isn’t too big) and because they tend to fail and require fixing (more surgery). This not my kind of PE.

Let me try to clarify this for you guys.

1500 mm Hg was the pressure induced in the corpora cavernosa.

Normal pressure in the corpora cavernosa during erection cannot be above arterial blood pressure, which is 120 mm Hg in a healthy adult.

The consequence for pe: the comparison is with jelq & clamp (not with stretch & hang!): permanent deformation of the tunica with penis penis deformation would occur at more than 10 times normal blood pressure.

100 mm Hg = 3.94 inch Hg.

Later - ttt

Thank you ttt, but what you say about pressure in the CC is known by measure token in the penis or are you supposing that CC pressure can’t be higher than arterial blood pressure. Aren’t mechanism of erection able to lead to higher local pressure (in the penis)?

Originally Posted by marinera
Thank you ttt, but what you say about pressure in the CC is known by measure token in the penis or are you supposing that CC pressure can’t be higher than arterial blood pressure. Aren’t mechanism of erection able to lead to higher local pressure (in the penis)?

No - arterial pressure is the max. Experimentally, of course, the pressure in the cc can be increased until the tunica blasts.

During jelq or clamp sessions the pressure can also be increased above arterial blood pressure, but not during a spontaneous erection (not even using viagra or intracarvernous prostaglandin injections.

Later - ttt

tt- I agree that 1500 mmHg is a rather excessive pressure to generate in the corpus cavernosa to cause TA deformation or rupture. You must keep in mind that this was an experiment by urologist who place inflatable prostheses into patients. They have to know how much pressure to generate within them in order to assess what amount of fluid they will fill the reservoir (described above) which the patient pumps into the prosthetic chambers to achieve erection. But you are not correct that pressures within the corpus cavernosa and spongiosium at erection are no higher than peak systolic blood pressure (in your example 120 mmHg).

As the cavernosa fill with blood during the tumescent phase of erection, pressure rises. When the intracavernosal pressure rises above the diastolic pressure (the lower number in a blood pressure), blood filling occurs only at the peak of blood pressure until the pressure within the cavernosa reaches systolic blood pressure; the penis achieves complete erection. This is now the full erection phase. The pressure within the pudendal artery (which fills the penis) is slightly higher than systemic pressure so the pressure within the penis at the end of this phase is higher than pressure measured at the arm with a blood pressure cuff. “After full erection is achieved, contraction of the ischiocavernosus muscle (from activation of the somatic nerves) compresses the proximal corpora and raises the pressure in the entire corpora well above the systolic blood pressure, resulting in rigid erection. This rigid phase occurs naturally during masturbation or sexual intercourse but can also occur from slight bending of the penis, without muscular action…a result of contraction of the ischiocavernous muscle [which wraps around the crux or base of the penis at the ischium and when contracted it pushes blood towards the distal penis], the intracavernous pressure rises well above the systolic pressure [80 - 90 % higher than systolic blood pressure] resulting in rigid erection. During this phase, almost no blood flows through the cavernous artery; however, the short duration prevents the development of ischemia or tissue damage.” (From Chapter 37. Male Sexual Dysfunction > Male Sexual Dysfunction: Introduction, Lange’s Urology. Lange review series.) This reference was obtained from AccessMedicine). There is an excellent graph from Smith’s Urology, 16th edition that displays this rise in pressure leading to the rock hard penis we’ve all had (hopefully) . I’d love to attach it, BUT it’s copyrighted and requires permission to post here. If you want a copy, I’d be happy to email it to you.

So intracavernosa pressures can be higher than systemic pressure, but as you point out, never 1500 mmHg as the authors of this paper found when the TA burst.

Thunder - Thanks for the guidance.

I apologize for my overly technical and verbose explanation regarding blood pressures in the cavernosa at full erection. The point I wanted to get across was that after the cavernosa and spongiosum fill and reach a pressure equal to the blood pressure throughout the rest of the body, no more blood can enter as ticktickticker said. But part of the reflex that causes erections cause the Ischiocavernosus muscles to contract (located deep to the scrotum where the cavernosa anchor to the pelvic bone; they override the cavernosa at this anchoring point). This forces blood up into the rest of the cavernosa causing the erection to get firmer and stand out. This generates a pressure within the cavernosa 80 - 90% above the blood pressure in the rest of the body.

I should have said it this way in my prior post. I will in the future.

Deep from within penis growing labs of Thunder’s…

I often wonder how many PSI and how much “burst pressure” I’m exerting when I’m doing my stretches. Just joking guys. I love this forum. It’s one of the few places you can find people scientifically discussing penis growth like it’s a space launch. Anyone try using stem cells for PE yet? :)

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