Editing Ovulation (section)

=== Ovulation ===

[[Estrogen]] levels peak towards the end of the follicular phase, around 12 and 24 hours. This, by positive feedback, causes a surge in levels of [[luteinizing hormone]] (LH) and [[follicle-stimulating hormone]] (FSH). This lasts from 24 to 36 hours, and results in the rupture of the ovarian follicles, causing the oocyte to be released from the ovary.<ref>{{cite book| vauthors = Watson S, Stacy KM |chapter=The Endocrine System| veditors = McDowell J |title=Encyclopedia of Human Body Systems | volume = 1 |publisher=Greenwood |year=2010 |isbn=9780313391750 |pages=201–202 |chapter-url= https://books.google.com/books?id=7tt1C1aJ0G4C&pg=PA201 |access-date=2013-11-09}}</ref>

Through a signal transduction cascade initiated by LH, which activates the pro-inflammatory genes through cAMP secondary messenger, [[peptidase|proteolytic enzymes]] are secreted by the follicle that degrade the follicular tissue at the site of the blister, forming a hole called the ''stigma''. The [[secondary oocyte]] leaves the ruptured  follicle and moves out into the [[peritoneal cavity]] through the stigma, where it is caught by the [[Fimbria (female reproductive system)|fimbriae]] at the end of the [[fallopian tube]]. After entering the fallopian tube, the oocyte is pushed along by [[cilia]], beginning its journey toward the [[uterus]].<ref name=Marieb/>

By this time, the oocyte has completed [[meiosis|meiosis I]], yielding two cells: the larger [[ovum|secondary oocyte]] that contains all of the cytoplasmic material and a smaller, inactive first polar body. [[meiosis|Meiosis II]] follows at once but will be arrested in the [[metaphase]] and will so remain until fertilization. The [[spindle apparatus]] of the second meiotic division appears at the time of ovulation. If no fertilization occurs, the oocyte will degenerate between 12 and 24 hours after ovulation.<ref>{{cite journal | vauthors = Depares J, Ryder RE, Walker SM, Scanlon MF, Norman CM | title = Ovarian ultrasonography highlights precision of symptoms of ovulation as markers of ovulation | journal = British Medical Journal | volume = 292 | issue = 6535 | pages = 1562 | date = June 1986 | pmid = 3087519 | pmc = 1340563 | doi = 10.1136/bmj.292.6535.1562 }}</ref> Approximately 1–2% of ovulations release more than one oocyte. This tendency increases with maternal age. Fertilization of two different oocytes by two different spermatozoa results in fraternal twins.<ref name=Marieb/>

The precise moment of ovulation was captured on film for the first time in 2008, coincidentally, during a routine hysterectomy procedure. According to the attending gynecologist, the ovum's emergence and subsequent release from the ovarian follicle occurred within a 15-minute timeframe. <ref>{{cite news |url=http://news.bbc.co.uk/2/hi/health/7447942.stm |title=Ovulation moment caught on camera |date=2008-06-12 |publisher=BBC News}}</ref>