How long can hair grow? - Maksim Plikus — Transcript

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1. 0:06At age 44, Xie Qiuping cut her hair for the first time in over three decades.
2. 0:14At the time, her impressive locks extended over five meters—
3. 0:18earning the Guinness World Record for the world's longest hair.
4. 0:23But even with this record-setting feat,
5. 0:26her hair might not have reached its maximum possible length.
6. 0:30So just how long can human hair actually grow?
7. 0:35To get to the bottom of this question,
8. 0:37let's start at the bottom of a hair follicle.
9. 0:41Follicles are tube-shaped structures nestled roughly half a centimeter
10. 0:45below the skin's surface.
11. 0:47At their base is what's called the hair bulb,
12. 0:50and it contains rapidly dividing matrix cells.
13. 0:54As they divide, these develop into specialized hair cells called trichocytes,
14. 0:59which harden as they fill themselves with cable-like keratin proteins.
15. 1:03As more and more trichocytes are produced,
16. 1:06they form a strand of hair that emerges from the follicle and grows upwards.
17. 1:11All the hair on your body grows this way,
18. 1:13but not all hair will grow to the same length, shape, or color.
19. 1:18Those properties are determined by yet another type of cell
20. 1:21within the hair bulb: the fibroblast.
21. 1:25Fibroblasts instruct the matrix cells to grow specific kinds of hair
22. 1:29for each part of the body.
23. 1:31This is why doctors doing hair implants usually use follicles
24. 1:35from the same body part,
25. 1:37though they'll sometimes change things up.
26. 1:40For example, eyelashes are some of the shortest hairs on your body
27. 1:44at an average length of one centimeter.
28. 1:47So to give people longer eyelashes, doctors might implant scalp follicles,
29. 1:52which grow at a rate of about 15 centimeters per year.
30. 1:56So these patients will have to trim their new lashes regularly
31. 2:00to avoid a blinding curtain of hair.
32. 2:04In general, our follicles are very resilient.
33. 2:07Even if you pluck hair out with your fingers or some wax,
34. 2:10you’ll likely only damage matrix cells, not fibroblasts.
35. 2:15So given time, those hair bulbs will repair themselves
36. 2:18and begin producing new hair.
37. 2:20However, each strand of hair will only grow for so long.
38. 2:25We don't fully understand how follicles measure time,
39. 2:28but in most cases they'll stop growing a strand after 5 to 7 years.
40. 2:33This means that at the rate of 15 centimeters a year,
41. 2:37the average person’s scalp hair could reach a maximum length
42. 2:41of around one meter.
43. 2:43The precise duration and speed of hair growth varies from person to person
44. 2:48depending on genetics, hormones, and various health conditions,
45. 2:52and it’s difficult to know exactly what combination of these factors
46. 2:57let Xie Quiping reach her record.
47. 3:00But however long your locks may be, when a follicle stops growing,
48. 3:05the hair falls out— shedding from our heads slowly,
49. 3:09or in clumps during showers and hair brushing.
50. 3:13After a hair is lost, fibroblasts will trigger the growth of a new strand
51. 3:17to fill out your scalp— usually.
52. 3:20As we age, follicles run out of certain cell types,
53. 3:23which can lead to changes in hair growth.
54. 3:26For example, when they run out of pigment-producing melanocyte stem cells,
55. 3:31follicles begin producing gray hairs.
56. 3:34And since there are only a handful of melanocyte stem cells per follicle
57. 3:39to begin with,
58. 3:40they tend to run out relatively early in a person’s life.
59. 3:44Similarly, when follicles run out of epithelial stem cells,
60. 3:48they begin to shrink and grow shorter, thinner strands
61. 3:52before eventually shutting down production altogether.
62. 3:55This is what leads to baldness,
63. 3:57though the condition can also be accelerated by testosterone,
64. 4:00which can prevent fibroblasts’ instructions
65. 4:03from reaching a follicle’s cells.
66. 4:06While it’s completely natural for hair growth
67. 4:08to change over the course of our lives,
68. 4:10there are ways to take more control of our scalps.
69. 4:14Some baldness remedies remove excess testosterone,
70. 4:17and special shampoos can address the coarse, brittle strands
71. 4:21reported by many people with gray hair.
72. 4:24Since our bodies already produce hair at the fastest possible biological speed,
73. 4:29there's currently no way to grow hair faster.
74. 4:33But even if you’re unlikely to beat Xie Qiuping’s record,
75. 4:37with time, the right treatments, and some genetic luck,
76. 4:41you should be able to grow some luscious locks of your own.