Figure 1b. Diagrams illustrate the normal anatomy of the testis and testicular adnexa. (a) A dense, tightly adherent fibrous membrane, the tunica albuginea, surrounds the testis. The tunica albuginea invaginates the interior of the testis posteriorly to form an incomplete vertical septum, the mediastinum testis. Numerous fibrous septa radiate from the mediastinum toward the surface of the gland and separate the organ into multiple cone-shaped lobules that contain convoluted seminiferous tubules. As they approach the mediastinum, the seminiferous tubules straighten and unite to form 20-30 larger ducts, which then enter the fibrous tissue of the mediastinum and form an anastomotic network of channels that constitutes the rete testis. At the upper end of the mediastinum, the channels of the rete testis perforate the tunica albuginea and form 12-15 ducts called the efferent ductules, which enter the head of the epididymis. The epididymis, which connects the testis with the vas deferens, is attached to the testis posteriorly. It consists of three anatomic segments: the head (globus major), the body (corpus epididymidis), and the tail (globus minor). (b) The testis and epididymis are loosely invested by a serous membrane, the tunica vaginalis. Derived from the processus vaginalis of the peritoneum, this membrane consists of visceral and parietal layers. Three closely applied fascial layers surround the tunica vaginalis and extend cranially to envelop the structures of the spermatic cord: the internal spermatic fascia, the cremasteric fascia, and the external spermatic fascia. The internal spermatic fascia is a continuation of the transversalis fascia. The cremasteric layer consists of scattered muscle bundles within a fascial membrane that corresponds to the internal oblique muscle and its fascia. The external spermatic fascia is continuous at the superficial inguinal ring with the deep fascia that cover the aponeurosis of the external oblique muscle. The external covering of the testis is the scrotum, which consists of two layers, the tunica dartos and the skin. The tunica dartos is a highly vascular membrane containing a thin layer of nonstriated muscle fibers. In the midline, a septum extends inward from the dartos layer to divide the scrotal pouch into two cavities for the testes. (Fig 1b reprinted, with permission, from reference 1.) (c) Vestigial remnants of the testis, epididymis, and vas deferens. (Fig 1c reprinted, with permission, from reference 2.)