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Some technical/anatomical info on the tunica

Some technical/anatomical info on the tunica

This is basically a putting-together of some various tidbits in scentific (and otherwise) litterature that I’ve run across, either by my own searches or through links found at various boards. (You’ll excuse my lack of proper recognition for those who found some of this first, my organizing skills are good but sadly lacking on my computer.)

Basic anatomy:

“The tunica albuginea consists of layers of collagen which can accommodate a considerable degree of intracavernosal pressure prior to rupture. To function effectively, these fascial layers must provide the penis with a wall container capable of withstanding a high degree of rigidity and axial strength when erect, yet be supple when flaccid. The tunica must be able to elongate symmetrically and increase in girth with tumescence, assuring a straight erection. The tensile strength of the tunica is approximately 1200 - 1500 mmHg making this fascia one of the most strong in the body. Approximately 5% of the tunica is elastic which enables the penis to develop elongation. The average volume increase of the erect penis from the flaccid volume is 3-fold with a range from 1.7 - 5 fold. The mechanical properties of the tunica which allow for maximum volume changes of the erect penis are called tunica dispensability. Regions of the tunica with focal poor dispensability cause the erect penis to bend. This focal tunical abnormality in dispensability is called Peyronie’s disease.” (Sorry, no proper reference on website to link to.)

And the tunica is composed of two layers of collagenous tissue:

“The tunica albuginea of the penis(above) consists of two fibro-elastic connective tissue layers, an inner circular and an outer longitudinal. The inner circular connective tissue layer serves to contain the erectile tissue’s diameter during erection. […] The outer longitudinal layer is present to regulate the length of the expanding penis and it extends from the glans to the proximal crura of the penis where it inserts into the pubic ramus.” (link)

Recently I found this little gem of a study that really clears up one of the main wonders of the tunica for me (related to the first item under Pathology):

“We show here by electron microscopy and immunohistochemical approaches that the tunica albuginea of the human testis contains abundantly contractile elements. […] These data, demonstrating complex contraction and relaxation activities, are indicative of a major physiological role of the tunica albuginea presumably related to testicular sperm transport.” (Middendorff R, Muller D, Mewe M, Mukhopadhyay AK, Holstein AF, Davidoff MS. The tunica albuginea of the human testis is characterized by complex contraction and relaxation activities regulated by cyclic GMP - J Clin Endocrinol Metab. 2002 Jul;87(7):3486-99)


“(D)amage to the blood vessels leads to reduced levels of oxygen which results in increased collagen formation. This affects the elasticity in the penis by upsetting the balance between collagen and elastin in the penis. In the penis, the ideal ratio between collagen and smooth muscle (which contains elastin) is 48% (collagen) : 52% (smooth muscle which contains elastin). When this ratio is upset by an increased proportion of collagen (i.e. a relative decrease in the proportion of elastin) the penis becomes less elastic.” (Penile Geometry: Characteristics, physical and health related correlates - Boston University)

These last two references point to the importance of keeping the circulation in working order to retain penile fitness. (If you smoke, STOP NOW!!) Interesting to note is that the majority of sufferers of penile fractures (ruptured tunica) are 30-40 where general elasticity of collagenous is on a downward trend (and probably because sexual activity tends to dwindle as years pass as well). [This is also implied in a study on rats that show that age causes a thinning of the tunica with a resulting decrease in elastic fibers. (Shen ZJ, Jin XD, Chen ZD, Shi YH., Effect of aging on penile ultrastructure - Asian J Androl. 2001 Dec;3(4):281-4.)

“In 183 publications 1331 cases were reported between January 1935 and July 2001. […] The commonest causes were coitus and penile manipulations, especially masturbation. Most patients were in their fourth decade.” (Eke N., Fracture of the penis - Br J Surg. 2002 May;89(5):555-65)

We can also note that Peyronie’s disease, plaque buildup on the tunica due to limited elasticity resulting in a curvature, is more common that previously thought:

“Using previously validated questions the prevalence of Peyronie’s disease in the sample was 3.2%; this is much higher than indicated in previous reports. A comparably high prevalence is reported for diabetes and urolithiasis, suggesting that this ‘rare’ disease is more widespread than previously thought.” (Schwarzer U, Sommer F, Klotz T, Braun M, Reifenrath B, Engelmann U., The prevalence of Peyronie's disease: results of a large survey - BJU Int. 2001 Nov;88(7):727-30)

Hope you enjoyed the read.

2010-01-09: BPEL: 19,7cm [7.75"] EG: 15,0 cm [5.9"]

2010-04-24: BPEL: 20,4cm [8.0"] EG: [???]

Great post. Thanks Ebon.

Good info. Here’s a crosssection through a penis. It shows how thick the tunica is. It’s an anatomical picture, but not very scary (you know what I mean):

Attached Images
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