Morphology of the fallopian tube during the ovarian cycle

In the reproductive life of the non-pregnant female, the Fallopian tube functions to nourish and transport the ovum towards the uterus in a precisely timed manner. These processes are facilitated by cyclical changes in the mucosa and musculature layers of the Fallopian tube during the ovarian cycle. The volume of tubal fluid in the Fallopian tube also varies during the ovarian cycle. However, there is very little information on any morphological changes in the tubal vasculature which may be associated with the above mentioned variations in the tubal structure and function during the ovarian cycle. The aim of the present study was to investigate the morphology of tubal blood and lymph vessels in the different layers of the isthmus, ampulla and infundibulum, and to determine whether there were any cyclical changes occurring in the mucosa at the: (A) early/mid proliferative phase (B) late proliferative/ovulatory/early luteal phase and (C) mid/late luteal phase. For this purpose, the serosal, muscle and mucosal layers of the isthmus, ampulla and infundibulum were studied by light microscopy. In order to identify any possible cyclical changes in vascularity of the isthmus, ampulla and infundibulum, mucosal blood capillaries were counted in toluidine blue stained sections. Distinction between blood and lymph vessels was achieved using a blood vascular endothelial marker, CD34. Furthermore, any possible cyclical alterations in the fine structure of ampullary mucosal blood capillaries were examined by transmission electron microscopy. The serosal layer consisted of large arterioles and veins. In the muscle layer, when detected, small blood vessels were present. Mucosa consisted of two types of folds, branched and unbranched. Both types were present in the ampulla and infundibulum (fimbriae), whereas the isthmus consisted mainly of shorter and thicker unbranched folds. Arrangement of the different types of blood vessels was different in these two types of mucosal folds. Branched folds in the ampulla and infundibulum (fimbriae) contained arterioles, blood capillaries and venules. Arterioles were confined to the core and base of the folds, whereas blood capillaries and venules were distributed in all parts of these folds. Unbranched folds from the ampulla and infundibulum contained blood capillaries and venules. Isthmic unbranched folds contained only blood capillaries. The epithelial cells/blood capillary ratio was lowest in all three groups of the infundibulum compared with the ampulla and isthmus, the lowest being in Group A (4 epithelial cells/blood capillary). However, in Group A, the isthmus had the highest epithelial cells/blood capillary ratio (56 epithelial cells/blood capillary) compared to Group B and Group C in the three regions. These observations suggest that the isthmic mucosal folds may be least vascular and the infundibular (fimbrial) mucosal folds the most vascular prior to ovulation. Significant variations in the epithelial cells/blood capillary/fold ratio within each region and group (P