Fig. 8. A model describing ventral prostate induction. On the left-hand side is a UGT during the initial stages of prostatic induction. The SM layer is discontinuous and signalling between the VMP and urethra occurs. At E18.5, prostatic buds become visible, in males. On the upper right side of the figure is a female at E21.5, showing the SM layer has formed and that interaction between the VMP and urethra is prevented. Residual buds may be present, but these do not enter the VMP and eventually regress. On the lower right-hand side is a male at E21.5 showing a discontinuous SM layer, prostatic buds have emerged from the urethra and entered the VMP, where subsequent growth and branching morphogenesis takes place.