Cyclic changes in the human fallopian tube isthmus and their functional importance.

Morphologic studies in rabbits have indicated that a column of tenacious mucus occupies the isthmic lumen in estrus. This secretion disappears after ovulation, and cilia are prominent at the time of ovum transport through the isthmus. This study was designed to seek evidence of similar mucus in the human fallopian tube isthmus. Isthmic segments were taken from 18 normally ovulating women throughout the menstrual cycle. Specimens were also obtained from 10 other women further to elucidate endocrine dependence of observed morphologic variations. Appearances consistent with luminal isthmic mucus were obtained in two women in the late follicular phase and in one woman immediately after ovulation. Observable mucus was absent and cilia were prominent in women in the early follicular phase, in the luteal phase, postmenopausally, in late pregnancy, and in the puerperium. The results described are consistent with the hypothesis that differential sperm and ovum transport in the human fallopian tube isthmus is at least partially determined by the presence or absence of estrogen-dependent luminal mucus.