Vaginal epithelium menstrual cycle

A more permeable epithelium obviously facilitates greater absorption. Some epithelia are relatively more permeable than others. For example, the skin is an extremely impermeable barrier, whereas the permeability of the lung membranes towards many compounds is much higher than the skin and is also higher than that of the small intestine and other mucosal routes. The vaginal epithelium is relatively permeable, particularly at certain stages of the menstrual cycle. 

Fig. 3 Profile of the gonadotorpin and ovarian hormones during a normal menstrual cycle. The number of cell layers in the vaginal epithelium rises from 22 layers at approximately day 10 of the cycle to 45 layers at ovulation, and drops to 33 layers around day 20. (From Refs. - l)...

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