Figure 15.

Transverse sections of developing human prostate immunostained for smooth muscle α-actin. (A) is a section through the verumontanum of a 9-week pre-bud UGS in which sparse α-actin-positive cells (white arrowheads) are seen in ventral-lateral UGM, whereas α-actin-positive cells are abundant in the wall of the rectum. (B) is section of a human fetal prostate showing smooth muscle bundles in ventral UGM at 15 weeks of gestation. (C) is a section of a human fetal prostate at 19 weeks of gestation showing α-actin-positive smooth muscle around the periphery where solid epithelial cords are branching. WD= Wolffian duct, UGS= urogenital sinus, Ur= urethra, EJD=ejaculatory ducts.