FSH and (1) _______ stimulate cells outside the zona pellucida to secrete (2) _____. A(n) estrogen-containing fluid accumulates in the follicle, and estrogen levels in the blood begin to increase. About eight to ten hours before being released from the ovary, the (3) _____ completes Meiosis I. And then its (4) _____ divides, forming two cells.
One cell, the (5) ____ _____, ends up with nearly all the cytoplasm. The other cell is the first of three (6) _____ ______. The meiotic parceling of the chromosomes among all four cells gives the secondary oocyte a (7) ______ chromosome number - which is the exact number required for gametes and for (8) ____ reproduction.
About halfway through the menstrual cycle, the (9) _____ gland detects the rise in the blood level of estrogens. It responds with a brief outpouring of (10) _____. This (10) surge causes rapid vascular changes that make the (11) ____ swell quickly. The surge also induces (12) __________ to digest the bulging follicle wall. The weakened wall ruptures. Fluid escapes and carries the (13) ______ ______ with it. Thus, the midcycle surge of LH triggers (14) _____ - the release of a secondary oocyte from an ovary.
The estrogens released early in the menstrual cycle also help pave the way for a possible (15) _______. Estrogens stimulate growth of the (16) _____ and its glands. Just before the midcyle surge of LH, follicle cells start to secrete some (17) _____, as well as estrogens. Blood vessels grow rapidly in the thickened endometrium. At ovulation, the estrogens act on tissue around the (18) ________ canal. The cervix starts to secrete large quantities of a thin, clear (19) ______, which is an ideal medium for sperm to swim through.
A. secondary oocyte
P. polar bodies