Shortly before ovulation, fimbriae of the oviduct begin to sweep over the surface of the ovary, and the tube itself begins to contract rhythmically It is thought that the oocyte surrounded by some granulosa cells (Figs. 2.3 and 2.4) is carried into the tube by these sweeping movements of the fimbriae and by motion of cilia on the epithelial lining. Once in the tube, cumulus cells withdraw their cytoplasmic processes from the zona pellucida and lose contact with the oocyte.
Once the oocyte is in the uterine tube, it is propelled by cilia with the rate of transport regulated by the endocrine status during and after ovulation. In humans, the fertilized oocyte reaches the uterine lumen in approximately 3 to 4 days.
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