<s>[INST] context: The wall of the vagina from the lumen outwards consists firstly of a mucosa of non-keratinized stratified squamous epithelium with an underlying lamina propria of connective tissue, secondly a layer of smooth muscle with bundles of circular fibers internal to longitudinal fibers, and thirdly an outer layer of connective tissue called the adventitia. Some texts list four layers by counting the two sublayers of the mucosa (epithelium and lamina propria) separately. The lamina propria is rich in blood vessels and lymphatic channels. The muscular layer is composed of smooth muscle fibers, with an outer layer of longitudinal muscle, an inner layer of circular muscle, and oblique muscle fibers between. The outer layer, the adventitia, is a thin dense layer of connective tissue, and it blends with loose connective tissue containing blood vessels, lymphatic vessels and nerve fibers that is present between the pelvic organs.The epithelial covering of the cervix is continuous with the epithelial lining of the vagina. The vaginal mucosa is absent of glands. The vaginal epithelium consists of three rather arbitrary layers of cells - superficial flat cells, intermediate cells and basal cells - and estrogen induces the intermediate and superficial cells to fill with glycogen. The superficial cells exfoliate continuously and basal cells replace them Under the influence of maternal estrogen, newborn females have a thick stratified squamous epithelium for two to four weeks after bih. After that, the epithelium remains thin with only a few layers of cells without glycogen until pubey, when the epithelium thickens and glycogen containing cells are formed again, under the influence of the girl's rising estrogen levels. Finally, the epithelium thins out during menopause onward and eventually ceases to contain glycogen, because of the lack of estrogen In abnormal circumstances, such as in pelvic organ prolapse, the vaginal epithelium may be exposed becoming dry and keratinized [/INST] question: Vaginal epithelium is derived from: | options: A: Endoderm of urogenital sinus B: Mesoderm of urogenital sinus C: Endoderm of genital ridge D: Mesoderm of genital ridge | answer: A </s>