The scrotum is a fibromuscular sac divided into two compartments by a median raphe. Its wall is composed (from superficial to deep) by skin, superficial fascia, dartos muscle, external spermatic fascia, cremasteric fascia, and internal spermatic fascia. The raphe is continuous with the dartos muscle. Beneath the internal spermatic fascia, there is the tunica vaginalis, a mesothelial layer which outlines a sac containing a testis, epididymis, and spermatic cord, usually together with a small amount of fluid. The layer of the tunica vaginalis lining the scrotal wall is defined as the parietal layer; the one extending over the testis and epididymis is called the visceral one. The two layers join at the posterolateral aspect of the testis, where the tunica attaches to the scrotal wall. Beneath the visceral layer of the tunica vaginalis is the tunica albuginea, an inelastic structure which covers the testis and, at its posterior surface, projects into the inner part to form an incomplete septum, the mediastinum; from there, multiple thin fibrous septa extend into the testicular parenchyma, dividing it into 200-400 lobules. Each lobule contains one to three seminiferous tubules which, at the mediastinum, open via the tubuli recti into dilated spaces called the rete testis and then drain into the epididymis through 10-15 efferent ductules. The epididymis, a tubular structure consisting of a head, body, and tail, is located superior to and contiguous with the posterior aspect of the testis. After entering the epididymal head, the ductules from the rete testis form a single duct, the ductus epididymis, which has very tortuous course from the head to the tail (up to 6 m). The ductus finally becomes the vas deferens and continues in the spermatic cord.
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