Fig. 7. Horizontal sections of two fetuses at 9 weeks after differentiation of urogenital sinus into the bladder and urethra. (A, B) A specimen of crownrump length (CRL) 39 mm. (C, D) A specimen of CRL 35 mm. Hematoxylin and eosin staining. The upper side of each panel corresponds to the posterior side of the pelvis. Panels A (or panel C) displays the plane 0.6 mm (or 0.8 mm) superior to panel B (or D), respectively. In both specimens, smooth muscles (stars) are evident in the bladder anterior wall (BL). In panels A and B (or C and D), the Wolffian duct (WD) opening is located 0.6 mm (or 0.8 mm) inferior and 0.1 mm medial side of the ureteral opening (UR). All panels were prepared at the same magnification. Scale bar in panel A=1 mm. LA, levator ani muscle; MD, Műllerian duct or paramesonephric duct; OE, obturator externus muscle; OI, obturator internus muscle; P, pubis; PC, peritoneal cavity; PX, pelvic autonomic nerve plexus; R, rectum; UA, umbilical artery; UTH, urethra.