Anatomy of the testicle

The average adult testicle is paired and measures 4x3x2.5cm(2).

Figure 1: Anatomy of the testicle(3)

During embryological development, the testis descends from the posterior abdominal wall, through the inguinal canal to the scrotum. The nervous and arterial supply and the venous and lymphatic drainage travel the same route in the spermatic cord. The testis is suspended in the scrotum by the spermatic cord(3).

Figure 2: Bell Clapper Deformity by Todd Buck(17)

The tunica vaginalis is derived from the abdominal peritoneum and separates the testis and epididymis from the scrotal wall. It covers the exterior anterolateral aspect of the testis, fully surrounding the testis and fixing it to the posterior wall. Fluid may accumulate in the tunica vaginalis leading to hydrocele (water), haematocele (blood) or pyocele (pus).

In the ‘bell-clapper’ deformity, there is high investment of the tunica vaginalis, leading to a horizontal lie and increased free space for the testicle to move (figure 2). This can then lead to testicular torsion as the spermatic cord twists cutting of the blood supply to the testicle. It is thought approximately 10% of the male population have this deformity, but torsion happens less frequently, with no clear triggering event identified(4).

The tunica albuginea is a dense fibrous fascia that encloses the testis. Posteriorly it penetrates the parenchyma of each testis forming the mediastinum and separating each testis into approximately 250 lobules.

The functions of the testes are sperm production and hormone synthesis. Each lobule contains 1-4 convoluted seminiferous tubules The basement membrane of these tubules contain 2 cell types: Sertoli cells, which support the structure and spermatogenic cells which produce sperm. The stroma between the cells contains connective tissue which contains the Leydig cells; these are responsible for producing testosterone in response to luteinising hormone (LH).

Once produced in the seminiferous tubules, the developing spermatozoa collect in the rete testis before travelling via the efferent tubules to the epididymis for storage. The epididymis sits in the postero-lateral aspect of the superior pole of the testes. (3)

The testicular appendages (the appendix testis and appendix epididymis) are embryological remnants that serve no purpose but may twist and cause pain. This is common in pre-pubescent boys and doesn’t require surgical intervention if the diagnosis is certain

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