A morphologist's approach to the vagina.

The author reviews basic facts on vaginal histology and ultrastructure with respect to passage of different substances and drugs through the epithelium. Particular interest is given to the action mechanism of topically applied intravaginal estrogen, its binding to receptors in different vaginal cell types, and possible local metabolic routes for estrogen. Differences in estrogen sensitivity between uterus and vagina are discussed as well as the background for the high sensitivity in the vagina.