the stage of the follicle in the middle of the 28 day cycle. by this point rising estrogen levels become highly stimulatory and a sudden burstlike release of LH triggers ovulation. this causes the secondary oocyte to be extruded and journey down the uterine tube to the uterus. if pemetrated en route by a sperm, the secondary oocyte will undergo meiosis II, producing one large ovum and a tiny second polar body. if sperm penetration does not occur, the secondary oocyte simply disintegrates.