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The tunica albuginea is a connective tissue or fibrous envelope located in the penis. It is an integral part of the male reproduction system and, by extension, the genitourinary system, which comprises the reproduction and the urinary systems. This anatomical term is of Latin origin. "Tunica" means "covering" or "coat." This refers to the tunica albuginea's dense, white membranous layer, which consists of bundles of interlaced tissue. "Albuginea" means "white," as in the white part of an egg, which is called the albumen.
The tunica albuginea covers a part of the penis called the corpora cavernosa. This is a spongy chamber that traps the amount of blood required for achieving an erection, a state necessary for sexual intercourse. Working with the corpora cavernosa is Buck's fascia, which compresses the blood traveling through the deep dorsal vein of the penis located beneath it. This tissue is thus responsible for maintaining the erection made possible by the tunica albuginea. Buck's fascia, which is named after the American Civil War-era plastic surgeon Gurdon Buck, actually acts as the envelope of the tunica albuginea.
The penis is not the only part of the body with the tunica albuginea tissue. Its connective structure, the testis, also has this fibrous covering. In this case, however, it is of a blue-white hue rather than a strictly white color. It is covered by the tunica vaginalis, which is a membrane that expands over the front and sides of the testis. It does not, however, cover the tunica albuginea at the epididymis, which is a slender tube of the male reproductive organ's spermatic duct system. It is also absent at the posterior border of the testis, which is where the spermatic vessels enter the organ.
The inner layer of the tunica albuginea testis is covered by the tunica vasculosa. This is the vascular layer of this part of the penis, so named because it has a network of blood vessels. It is bound together by a loose, delicate and spongy substance called areolar tissue.
Additionally, the tunica albuginea is not restricted to the male reproduction system. The ovaries of the female reproductive system has the tissue in thick applications, consisting of short fibers with spindle-like cells. The tissue is covered with germinal epithelium, which is a single layer made up of cells shaped like cubes and possessing large, sphere-shaped nuclei.