Fig. 2. Sagittal sections of two fetuses after differentiation of urogenital sinus into the bladder and urethra. (A–C) A specimen of crown-rump length (CRL) 56 mm (10 weeks). (D, E) A specimen of CRL 65 mm (12 weeks). Hematoxylin and eosin staining. The left-hand side of each panel corresponds to the anterior side of the pelvis. Panel (A) (panel D) is the most medial side of panels (A–C) (panels D and E). Intervals between panels are 1.1 mm (A–B), 1.5 mm (B–C), and 0.5 mm (D–E), respectively. All panels were prepared at the same magnification. Scale bar in panel A=1 mm. (A–C) The Wolffian duct (WD) opening (arrow) is located 2.2 mm inferior and 2.6 mm medial side of the ureteral opening (arrowhead; UR). (D) The WD opening (arrow) is located 1.9 mm inferior and less than 0.1 mm medial side of the ureteral opening (arrowhead). Smooth muscles are seen in the bladder wall (BL in all panels; dark red color), while the urethra (UTH) accompanies the rhabdophincter (RS in panels B, D, and E). The prostate (PR) starts developing as sprouts from the urethra in both specimens. EAS, external anal sphincter; IL, ileum of the intestine; P, pubis; PC, peritoneal cavity; PX, pelvic autonomic nerve plexus; R, rectum; RA, rectus abdominis muscle; UA, umbilical artery; VAS, vas deferens.