part of part of has part has part develops from develops from membranous layer testis mesothelium mesoderm-derived structure reproductive structure peritoneal vaginal process tunica vaginalis testis http://upload.wikimedia.org/wikipedia/commons/4/4d/Gray1148.png UBERON:0006650 Wikipedia:Tunica_vaginalis EMAPA:19179 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 testis tunica vaginalis The outer coelomic epithelial covering of the testis; a sac of serous tissue covering the testis and the epididymis within which the testis can move about; it covers the tunica albuginea. SCTID:367713008 NCIT:C33822 lamina parietalis 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] tunica vaginalis testis tunica vaginalis of testis SCTID:362281009 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. FMA:15863 FMA:19844 processus vaginalis testis lamina visceralis MA:0003253 tunica vaginalis