Tunica albuginea basics
Anyone interested in Peyronie’s disease sooner or later comes across the term "tunica albuginea" and wonders just what it means and what it looks like.
Can you picture a sausage or hot dog that has a tube of casing around it? Well, the tunica albuginea is like the casing of that sausage. To be more accurate, penis anatomy is just like two such sausages that are parallel and touching each other along the midline. At the point where the two sausages touch, there is a normal vertical thickening or density of the casing material exactly in the midline of the penis. This thickened area is called a septum, and it is more vulnerable to injury than other areas of the tunica; for this reason, if the septum of the tunica albuginea is injured it will cause a straight upward or straight downward curvature. If other areas of the tunica albuginea are injured on the sides, then a lateral penile curvature occurs. If several injuries develop in different parts of the tunica, then combinations and twists develop.
The pronunciation of tunica albuginea is easy: tunica (too-nick-ah) albuginea (al-bu-gin-e-ah). The term itself is like many anatomy terms of Latin origin – tunica (covering, like a tunic that a person might wear) and albuginea (white, like the albumen in an egg white, or like white alabaster).
There are actually three different areas of the body where a tunica albuginea is found:
• Tunica albuginea of the penis, the tough thin fibrous layer of connective tissue that surrounds the deep corpora cavernosa of the penis
• Tunica albuginea of the testicles, the layer of connective tissue covering each of the two testes of the male
• Tunica albuginea of the ovary, the connective tissue immediately surrounding each of the two ovaries of the female
Peyronie’s disease, the tunica albuginea and you
The tunica albuginea that is important to Peyronie’s disease is found covering the two elongated erectile bodies of the penile shaft, called the corpora cavernosa. Think of it as the casing or covering of a sausage; in the case of the penis, there are actually two of these elongated bodies situated side by side – with a partition between them that is called a septum. The third long chamber of the penis sits below the two corpora cavernosa, and is only slightly erectile. It is called the corpora spongiosum, and within it passes the urinary passage way called the urethra.
Primarily the tunica albuginea is made of 95% collagen material, composed of amino acids (lysine, proline, glycine, alanine, and a few others). The other 5% or so of the tunica albuginea is elastin fibers (glycine, valine, alanine, and proline). The tissue that results from this protein combination is thin, tough and flexible.
A Peyronie’s plaque or scar is nothing more than an excess layer of disorganized and thickening of the collagen fibers that make up the tunica albuginea. It is often said that the PD scar is simply an overactive and excessive response to injury. The injury can be one large injury, or many small injuries over time.
There is another layer of tissue that is slightly deeper than the tunica albuginea, known as Buck’s fascia, and it also surrounds these two sausage-like chambers of the penis. These two layers of tissue are not directly connected to each other, but they essentially lay next to each other , like two blankets, one on top of the other. It is important to keep in mind that while the tunica albuginea does not have a nerve supply, Buck’s fascia does have a nerve supply. Buck’s fascia branches off at various points to go down deeper into the substance of the penis to surround individual muscles fibers and blood vessels of the penis. When and if a case of Peyronie’s disease experiences variable pain it is because Buck’s fascia is being stretched and pressed down upon by the small elevated or flat beads, lumps, bands of slightly to greatly dense and hard plaque or scar tissue. These soft tissue masses are located in the tunica albuginea, but do not directly cause the actual Peyronie’s pain because it has no nerve supply. Any Peyronie’s pain originates from the many pain fibers found in Buck’s fascia, just below the tunica albuginea. When pain is not present it is because Buck’s fascia is not being irritated by the scar or plaque material.
For a more comprehensive discussion of this topic, please visit Peyronie’s pain.
The tunica albuginea is not directly involved in maintaining an erection; that is due to Buck’s fascia constricting the deep dorsal vein of the penis, preventing blood from leaving and thus sustaining the erect state. The tunica albuginea assists in creating the tension or hardness of an erection because the expanding penis tissue that fills with blood presses against the tunica to create the hydrostatic pressure necessary for the erection to occur.