The three-dimensional architecture of the myosalpinx in the rabbit as revealed by scanning electron microscopy

The three-dimensional (3-D) architecture of the myosalpinx in the rabbit has been investigated by means of scanning electron microscopy after microdissection and the removal of interstitial connective tissue with KOH digestion. In the extramural portion of the tubo-uterine junction, the myosalpinx presents outer longitudinal bundles which form a well-defined continuous muscular layer extending towards the ampulla. Underlying this layer there are single muscular bundles which follow an uneven circular arrangement. At a deeper level the same bundles present a plexiform arrangement. Several bundles reach the base of the mucous folds and follow a discontinuous, approximately longitudinal arrangement. In the isthmus, the myosalpinx shows superficial longitudinal strips that abruptly bend sideways as they approach the ampulla, thereby enveloping the underlying muscular structure. The latter is arranged in the same way as at the extramural portion of the tubo-uterine junction, except for the lack of the outer longitudinal layer originating from the uterus. Our 3-D results revealed that the architecture of the rabbit myosalpinx consists of muscular bundles independent of one another that follow multiple spatial arrangements and form a complex network. Such a type of structure seems to be capable of stirring rather than pushing the embryo and gametes.