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The reproductive cyle begins with ovulation, the release of a ripe egg, or ovum, from the ovary
Hundreds of thousands of follicles sit nestled inside the ovary.
Each follicle is a sphere of cells with an immature egg at its center.
The typical 28-day menstrual cycle begins on the first day of menstrual bleeding.
During the first 7 days of the cycle, a few follicles start to grow.
These maturing follicles secrete estrogen hormone into the blood stream
to prepare the lining of the uterus for pregnancy.
Around Day 7, all of the follicles stop growing and begin to degenerate except for one.
This dominant follicle continues to grow, nourishing the developing egg inside it.
Around Day 12, the follicle secretes a surge of estrogen into the blood stream.
When the estrogen reaches the hypothalamus and the pituitary gland in the brain,
the anterior or front part of the pituitary gland floods the blood stream with luteinizing hormone.
Around day 14, luteinizing hormone causes the follicle to undergo a sudden growth spurt.
Right before ovulation, the egg detaches from the inside of the follicle.
The bulging follicle releases chemicals,
signaling one of the two fallopian tubes to move in closer and envelope the follicle.
The follicle swells until... it bursts open,
ejecting the ovum and fluid from the follicle into the abdominal cavity.
In response, the fimbriae, tiny finger-like projections
at the end of the fallopian tube, sweep across the ovulation site and pick up the ovum.
Microscopic cilia on the fimbrial surface guide the ovum to the entrance of the fallopian tube.
Muscular contractions along the wall of the fallopian tube
gently propel the ovum toward the uterus.
The ovum lives for 12-24 hours,
the interval when fertilization can occur.
If not fertilized, the ovum will disintegrate
and be shed along with the uterine lining during ***,
marking the end of one reproductive cycle and the beginning of another.