Layer Between Tunica Vaginalis and Tunica Albuginea
There is no distinct anatomical layer between the tunica vaginalis and the tunica albuginea—the visceral layer of the tunica vaginalis is the tunica albuginea. 1
Anatomical Clarification
The tunica vaginalis is a mesothelium-lined sac with two layers: a visceral layer (which directly adheres to and is synonymous with the tunica albuginea) and a parietal layer (which lines the scrotal cavity). 2
The tunica albuginea itself is the dense fibrous capsule of the testis, composed predominantly of collagen and elastic fibers, and represents the visceral layer of the tunica vaginalis. 3, 4
Deep to the tunica albuginea lies the tunica vasculosa, an innermost vascular layer that sits between the tunica albuginea and the testicular parenchyma. 3, 4
Embryological Context
During testicular descent (between 25 and 35 weeks of gestation), the testis draws with it an extension of the peritoneal lining called the processus vaginalis. 1
Normally, the processus vaginalis obliterates and involutes, leaving no communication between the peritoneal cavity and the scrotum; this involuted enveloping layer becomes the tunica vaginalis. 1
The visceral layer of this tunica vaginalis remains adherent to the testis as the tunica albuginea, while the parietal layer lines the inner scrotal wall. 2
Clinical Relevance
Understanding this anatomy is critical in scrotal trauma: disruption of the tunica albuginea (the visceral tunica vaginalis) leads to testicular rupture with extrusion of seminiferous tubules, requiring urgent surgical repair. 5, 6
In orchiopexy procedures, fixation is achieved by creating scarification between the tunica albuginea (visceral tunica vaginalis) and the parietal tunica vaginalis or surrounding structures. 7
Pathologic processes such as mesothelioma, adenomatoid tumors, and reactive inflammatory conditions can arise from the mesothelial cells of the tunica vaginalis layers. 8, 2