Embryology and anatomy of the vagina.

Abstract

Carcinoma of the cervix uteri may originate in the epithelium of the vaginal portion of the cervix. Female pseudohermaphroditism is absence of the lower portion of the vagina. The original vaginal epithelium is derived from the fused Mullerian ducts. It is replaced during prenatal life by entoderm from the urogenital sinus and/or by ectoderm from the p roctodeum. The Mullerian ducts develop in human embryos of 37 days ovu lation age. The Wolffian ducts induce the formation of the Mullerian du cts. In the embryo the Mullerian ducts approach each other and fuse in the midline to produce the uterovaginal canal. A solid mass of epitherlium derived from the uterovaginal canal and in part from the urogenital sinus is designated the primitive vaginal plate. The replacement of the origianl vaginal epithelium by the definitive epithelium is finished by the 140 mm stage. The definitive vaginal epithelium is derived from the ectoderm of the cloacal membrane and/or proctodeum. The final vaginal epithelium undermines the Mullerian epithelium which disappears. When androgen is introduced into the circulation of a female fetus induced abnormalities include absence of the lower part of the vagina. This involves the abnormal persistence of the urogenital sinus. The growth of the human vagina during prenatal life reflects the action of the hormones of pregnancy. The sharp dip in the growth curve during early postnatal life reflects the lack of these hormones. The relatively large size of the vagina at term is correlated with the descent of the bladder.