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