How menstruation works - Emma Bryce — Transcript

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1. 0:06This might seem hard to believe, but right now,
2. 0:10300 million women across the planet are experiencing the same thing:
3. 0:14a period.
4. 0:16The monthly menstrual cycle that leads to the period
5. 0:18is a reality most women on Earth will go through in their lives.
6. 0:22But why is this cycle so universal?
7. 0:25And what makes it a cycle in the first place?
8. 0:29Periods last anywhere between two and seven days,
9. 0:32arising once within in a 28-day rotation.
10. 0:35That whole system occurs on repeat,
11. 0:37happening approximately 450 times during a woman's life.
12. 0:42Behind the scenes are a series of hormonal controls
13. 0:45that fine tune the body's internal workings
14. 0:48to make menstruation start or stop during those 28 days.
15. 0:52This inner machinery includes two ovaries
16. 0:55stocked with thousands of tiny sacks called follicles
17. 0:58that each contain one oocyte, an unfertilized egg cell.
18. 1:03At puberty, ovaries hold over 400,000 egg cells,
19. 1:06but release only one each month,
20. 1:08which results in pregnancy or a period.
21. 1:12Here's how this cycle unfolds.
22. 1:14Each month beginning around puberty,
23. 1:16the hormone-producing pituitary gland in the brain
24. 1:19starts releasing two substances into the blood:
25. 1:22follicle stimulating hormone and luteinizing hormone.
26. 1:26When they reach the ovaries,
27. 1:27they encourage the internal egg cells to grow and mature.
28. 1:31The follicles respond by pumping out estrogen.
29. 1:34The egg cells grow and estrogen levels peak,
30. 1:37inhibiting the production of FSH,
31. 1:40and telling the pituitary to pump out more LH.
32. 1:43That causes only the most mature egg cell from one of the ovaries
33. 1:47to burst out of the follicle and through the ovary wall.
34. 1:50This is called ovulation,
35. 1:52and it usually happens ten to 16 days before the start of a period.
36. 1:56The tiny oocyte moves along the fallopian tube.
37. 1:59A pregnancy can only occur if the egg is fertilized by a sperm cell
38. 2:04within the next 24 hours.
39. 2:06Otherwise, the egg's escapade ends,
40. 2:08and the window for pregnancy closes for that month.
41. 2:11Meanwhile, the now empty follicle begins to release progesterone,
42. 2:16another hormone that tells the womb's lining
43. 2:18to plump up with blood and nutrients
44. 2:20in preparation for a fertilized egg that may embed there and grow.
45. 2:25If it doesn't embed,
46. 2:26a few days later, the body's progesterone and estrogen levels plummet,
47. 2:30meaning the womb stops padding out and starts to degenerate,
48. 2:34eventually falling away.
49. 2:37Blood and tissue leave the body, forming the period.
50. 2:41The womb can take up to a week to clear out its unused contents,
51. 2:45after which, the cycle begins anew.
52. 2:48Soon afterwards, the ovaries begin to secrete estrogen again,
53. 2:51and the womb lining thickens,
54. 2:53getting ready to accommodate a fertilized egg
55. 2:56or be shed.
56. 2:57Hormones continually control these activities
57. 3:00by circulating in ideal amounts delivered at just the right time.
58. 3:05The cycle keeps on turning,
59. 3:06transforming each day and each week into a milestone along its course
60. 3:11towards pregnancy or a period.
61. 3:13Although this cycle appears to move by clockwork,
62. 3:16there's room for variation.
63. 3:18Women and their bodies are unique, after all.
64. 3:20Menstrual cycles occur at diffferent times in the month,
65. 3:24ovulation comes at various points in the cycle,
66. 3:27and some periods last longer than others.
67. 3:30Menstruation even begins and ends at different times in life
68. 3:33for different women, too.
69. 3:35In other words, variations between periods are normal.
70. 3:39Appreciating these differences and learning about this monthly process
71. 3:42can empower women,
72. 3:44giving them the tools to understand and take charge of their own bodies.
73. 3:48That way, they're able to factor this small cycle
74. 3:51into a much larger cycle of life.