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The tunica vaginalis is the serous covering of the testis. It is a pouch of serous membrane, derived from the saccus vaginalis of the peritoneum, which in the fetus preceded the descent of the testis from the abdomen into the scrotum. After its descent, that portion of the pouch which extends from the abdominal inguinal ring to near the upper part of the gland becomes obliterated; the lower portion remains as a shut sac, which invests the surface of the testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and a parietal lamina.

we follow FMA is classifying as membranous layer - but this does not account for relationship to mesolthelium (subclass or has part?). The FMA also has 'sac of tunica vaginalis', which is a serous sac.[FMA]

uberon

processus vaginalis testis, tunica vaginalis, lamina parietalis, tunica vaginalis testis, lamina visceralis

UBERON:0006650

tunica vaginalis testis has two layers: visceral and parietal; the visceral layer lies on the anterolateral surface of the testis and epididymis; the parietal layer lines the inner surface of the scrotal sac

• cremaster muscle

• appendix testis