Video Essay Oocyte Pickup by the Mammalian Oviduct□V

Mammals ovulate an oocyte cumulus complex (OCC), which contains, in addition to the oocyte, numerous cumulus cells and an extensive extracellular matrix (Mahi-Brown and Yanagimachi, 1983; Talbot and DiCarlantonio, 1984). OCCs are ovulated into the peritoneal or bursal cavity and then picked up by the infundibulum of the oviduct and carried into the ampulla where fertilization occurs (Harper, 1994; Hunter, 1994). Pickup of the OCC by the oviduct is the first in an important series of gamete transport events that assure entry of blastocyts into the uterus at the proper time for implantation. The infundibulum has a highly convoluted surface characterized by numerous deep crevices and ridges leading to the opening or ostium through which the OCC enters the oviduct (Figure 1A). The epithelium on the exterior surface of the infundibulum is enriched with cilia that beat in the direction of the ostium (Figure 1B). Although these cilia create currents capable of moving small particles such as Lycopodium spores (Norwood, et al., 1978), ciliary currents alone cannot move larger objects, such as OCCs (0.7–1.0 mm diameter), into the ostium. Pickup of OCCs occurs by means of an adhesive interaction between the OCC and cilia coupled with ciliary beating that pulls the OCC toward the ostium (Norwood, et al., 1978). The following video sequences show the two mechanisms that allow particles to be moved by the cilia on the outer surface of the infundibulum and the importance of adhesion in OCC pickup.