Why do we cry? The three types of tears - Alex Gendler

6,829,697 views ใƒป 2014-02-26

TED-Ed


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

ืชืจื’ื•ื: Ido Dekkers ืขืจื™ื›ื”: Tal Dekkers
00:06
Our story is about a girl named Iris.
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ื”ืกื™ืคื•ืจ ืฉืœื ื• ื”ื•ื ืขืœ ื™ืœื“ื” ื‘ืฉื ืื™ืจื™ืก.
00:09
Iris is very sensitive.
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ืื™ืจื™ืก ื”ื™ื ืžืื•ื“ ืจื’ื™ืฉื”.
00:12
(Bird cawing)
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00:13
So much that she is always in tears.
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ื›ืœ ื›ืš ืจื’ื™ืฉื” ืฉื”ื™ื ื›ืœ ื”ื–ืžืŸ ื“ื•ืžืขืช.
00:16
She cries when she's sad,
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ื”ื™ื ื‘ื•ื›ื” ื›ืฉื”ื™ื ืขืฆื•ื‘ื”,
00:20
when she's happy,
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ื•ื›ืฉื”ื™ื ืฉืžื—ื”,
00:21
(Godzilla roars)
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00:23
and even tears up when things just get to her.
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ื•ืืคื™ืœื• ื“ื•ืžืขืช ื›ืฉื“ื‘ืจื™ื ื ื•ื’ืขื™ื ื‘ื”.
00:28
She has special lacrimal glands to make new tears
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ื™ืฉ ืœื” ื‘ืœื•ื˜ืช ืœืงืจื™ืžืœ ืžื™ื•ื—ื“ืช ื›ื“ื™ ืœื™ื™ืฆืจ ื“ืžืขื•ืช ื—ื“ืฉื•ืช
00:31
and special tubes, called lacrimal puncta,
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ื•ืฆื™ื ื•ืจื™ื•ืช ืžื™ื•ื—ื“ื•ืช, ืฉื ืงืจืื•ืช ืœืงืจื™ืžืœ ืคื•ื ืงื˜ื”,
00:33
to drain old ones away.
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ื›ื“ื™ ืœื ืงื– ืืช ื”ื™ืฉื ื•ืช.
00:36
And she cries so much that she goes through
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ื•ื”ื™ื ื‘ื•ื›ื” ื›ืœ ื›ืš ื”ืจื‘ื” ืฉื”ื™ื ืขื•ื‘ืจืช
00:38
ten ounces of tears per day,
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285 ื’ืจื ืฉืœ ื“ืžืขื•ืช ื›ืœ ื™ื•ื,
00:41
thirty gallons a year!
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ืžืื” ื•ืขืฉืจื™ื ืœื™ื˜ืจ ื‘ืฉื ื”!
00:43
In fact, if you look closely,
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ืœืžืขืฉื”, ืื ืชื‘ื™ื˜ื• ืžืงืจื•ื‘,
00:45
you'll see that she's crying a little bit all the time.
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ืืชื ืชืจืื• ืฉื”ื™ื ื‘ื•ื›ื” ืžืขื˜ ื›ืœ ื”ื–ืžืŸ.
00:49
The basal tears that Iris constantly produces
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ื”ื“ืžืขื•ืช ื”ื‘ื–ืืœื™ื•ืช ืฉืื™ืจื™ืก ืžื™ื™ืฆืจืช ื›ืœ ื”ื–ืžืŸ
00:52
form a thin coating of three layers
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ื™ื•ืฆืจื•ืช ืฆื™ืคื•ื™ ืขื“ื™ืŸ ืฉืœ ืฉืœื•ืฉ ืฉื›ื‘ื•ืช
00:54
that cover her and keep dirt and debris away.
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ืฉืžื›ืกื” ืื•ืชื” ื•ืžืจื—ื™ืง ืืช ื”ืื‘ืง ื•ื”ืœื›ืœื•ืš.
00:58
Right next to Iris is the mucus layer,
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ืžืžืฉ ืœื™ื“ ืื™ืจื™ืก ื™ืฉ ืฉื›ื‘ื” ืจื™ืจื™ืช,
01:00
which keeps the whole thing fastened to her.
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ืฉืฉื•ืžืจืช ืขืœ ื›ืœ ื”ืขื ื™ื™ืŸ ืฆืžื•ื“ ืืœื™ื”.
01:03
On top of it is the aqueous layer,
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ืžืขืœื™ื” ื™ืฉ ืฉื›ื‘ื” ืžื™ืžื™ืช,
01:06
which keeps Iris hydrated, repels invasive bacteria,
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ืฉืฉื•ืžืจืช ืขืœ ืื™ืจื™ืก ืœื—ื”,
ื“ื•ื—ื” ื‘ืงื˜ืจื™ื•ืช ืคื•ืœืฉื ื™ื•ืช,
01:09
and protects her skin, or cornea, from damage.
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ื•ืžื’ื™ื ื” ืขืœ ื”ืขื•ืจ ืฉืœื”, ืื• ืงืจื ื™ืช, ืžื ื–ืง.
01:13
And, finally, there is the lipid layer,
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ื•ืœื‘ืกื•ืฃ, ื™ืฉ ืืช ื”ืฉื›ื‘ื” ื”ืœื™ืคื™ื“ื™ืช,
01:15
an oily outer film that keeps the surface smooth
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ืฉื›ื‘ื” ืฉื•ืžื ื™ืช ืฉืฉื•ืžืจืช ืขืœ ืคื ื™ ื”ืฉื˜ื— ื—ืœืงื™ื
01:18
for Iris to see through,
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ื›ื“ื™ ืฉืื™ืจื™ืก ืชืจืื” ื“ืจื›ื,
01:20
and prevents the other layers from evaporating.
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ื•ืžื•ื ืขืช ืžื”ืฉื›ื‘ื•ืช ื”ืื—ืจื•ืช ืœื”ืชืื™ื™ื“.
ื‘ืื•ืคืŸ ื ื•ืจืžืœื™, ืื™ืจื™ืก ืžืžืฉื™ื›ื” ื‘ื™ื•ืžื”
01:23
Normally, Iris goes about her day
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01:24
without really noticing the basal tears doing their thing.
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ื‘ืœื™ ืœืฉื™ื ืœื‘ ืœื“ืžืขื•ืช ื”ื‘ืื–ืœื™ื•ืช
ืฉืขื•ืฉื•ืช ืืช ืขื ื™ื™ื ืŸ.
01:28
That's kind of their whole point.
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ื–ื” ืคื—ื•ืช ืื• ื™ื•ืชืจ ื”ื ืงื•ื“ื”.
01:30
But one day, she meets a girl named Onion.
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ืื‘ืœ ื™ื•ื ืื—ื“, ื”ื™ื ืคื•ื’ืฉืช ื‘ื™ืœื“ื” ื‘ืฉื ื‘ืฆืœ.
01:32
Iris is immediately smitten.
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ืื™ืจื™ืก ืžื•ืงืกืžืช ืžื™ื™ื“.
01:34
Onion looks gorgeous in her bright purple jacket,
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ื‘ืฆืœ ื ืจืื™ืช ื›ืœ ื›ืš ื™ืคื” ื‘ื–'ืงื˜ ื”ืกื’ื•ืœ ืฉืœื”,
01:37
and she smells terrific.
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ื•ื”ื™ื ืžืจื™ื—ื” ื ืคืœื.
01:39
So, Iris invites Onion to her house for dinner.
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ืื–, ืื™ืจื™ืก ืžื–ืžื™ื ื” ืืช ื‘ืฆืœ ืœื‘ื™ืช ืฉืœื” ืœืืจื•ื—ื”,
ืื‘ืœ ื›ืฉื”ื™ื ื‘ืื” ื•ืžื•ืจื™ื“ื” ืืช ื”ื–'ืงื˜ ืฉืœื”,
01:43
But when she comes in and takes off her jacket,
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01:45
something terrible happens.
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ืžืฉื”ื• ื ื•ืจืื™ ืงื•ืจื”.
01:47
You see, when Onion's jacket is removed,
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ืืชื ืžื‘ื™ื ื™ื, ื›ืฉื”ื–'ืงื˜ ืฉืœ ื‘ืฆืœ ืžื•ืกืจ,
01:49
a chemical reaction happens,
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ืชื’ื•ื‘ื” ื›ื™ืžื™ืช ืžืชืจื—ืฉืช,
01:51
converting the sulfoxides that make her smell so great
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ืฉืžืžื™ืจื” ืืช ื”ืชื—ืžื•ืฆื•ืช ื”ื’ื•ืคืจื™ืช ืฉื’ื•ืจืžื•ืช ืœื” ืœื”ืจื™ื— ื›ืœ ื›ืš ื˜ื•ื‘
01:54
into sulfenic acid,
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ืœื—ื•ืžืฆื” ื’ื•ืคืจื™ืชื™ืช,
01:56
which then becomes a nasty substance with a long name:
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ืฉืื– ื”ื•ืคื›ืช ืœื—ื•ืžืจ ื ื•ืจืื™ ืขื ืฉื ืืจื•ืš:
02:00
syn-Propanethial S-oxide.
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ืกื™ืŸ-ืคืจื•ืคื ื˜ื™ืืœ ืืก-ืื•ืงืกื™ื“.
ื”ื’ื– ืฆื•ืจื‘ ืืช ืื™ืจื™ืก,
02:04
The gas stings Iris, and suddenly, she can't help it,
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ื•ืคืชืื•ื, ื”ื™ื ืœื ื™ื›ื•ืœื” ืœื”ืชืืคืง,
02:07
she starts weeping uncontrollably.
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ื”ื™ื ืžืชื—ื™ืœื” ืœื‘ื›ื•ืช ืœืœื ืฉืœื™ื˜ื”.
02:10
These reflex tears are different from the basal tears
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ื”ื“ืžืขื•ืช ื”ืจืคืœืงืกื™ื‘ื™ื•ืช ืฉื•ื ื•ืช ืžื”ื“ืžืขื•ืช ื”ื‘ื–ืืœื™ื•ืช
02:13
that Iris is used to.
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ืฉืื™ืจื™ืก ืจื’ื™ืœื” ืืœื™ื”ืŸ.
02:14
Because they're designed
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ืžืคื ื™ ืฉื”ืŸ ืžืชื•ื›ื ื ื•ืช
02:16
to wash away harmful substances, or particles,
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ืœืฉื˜ื•ืฃ ืืช ื”ื—ื•ืžืจื™ื ื”ืžื–ื™ืงื™ื, ืื• ื”ื—ืœืงื™ืงื™ื,
ื”ืŸ ืžืฉื•ื—ืจืจื•ืช ื‘ื›ืžื•ื™ื•ืช ื’ื“ื•ืœื•ืช ื™ื•ืชืจ,
02:18
they're released in much larger amounts,
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02:21
and their aqueous layer contains more antibodies
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ื•ื”ืฉื›ื‘ื” ื”ืžื™ืžื™ืช ืฉืœื”ืŸ ืžื›ื™ืœื” ื™ื•ืชืจ ื ื•ื’ื“ื ื™ื
02:23
to stop any microorganisms that may be trying to get in, as well.
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ื›ื“ื™ ืœืขืฆื•ืจ ื›ืœ ืžื™ืงืจื•ืื•ืจื’ื ื™ื–ื ืฉืื•ืœื™ ืžื ืกื” ืœื”ื›ื ืก, ื’ื ื”ื•ื.
02:28
Both Iris and Onion are devastated.
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ื’ื ืื™ืจื™ืก ื•ื’ื ื‘ืฆืœ ื”ืจื•ืกื•ืช.
02:30
They know they can't continue their relationship
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ื”ืŸ ื™ื•ื“ืขื•ืช ืฉื”ืŸ ืœื ื™ื›ื•ืœื•ืช ืœื”ืžืฉื™ืš ืืช ื”ืงืฉืจ
ืื ืœืื™ืจื™ืก ื™ื›ืื‘ ื•ื”ื™ื ืชื‘ื›ื”
02:33
if Iris is going to hurt and cry every time Onion takes off her jacket.
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ื›ืœ ืคืขื ืฉื‘ืฆืœ ืชื•ืจื™ื“ ืืช ื”ื–'ืงื˜.
02:37
So, they decide to break up.
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ืื–, ื”ืŸ ืžื—ืœื™ื˜ื•ืช ืœื”ืคืจื“.
02:39
As Onion walks out the door, Iris stops crying.
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ื›ืฉื‘ืฆืœ ื™ื•ืฆืืช ืžื”ื“ืœืช,
ืื™ืจื™ืก ืžืคืกื™ืงื” ืœื‘ื›ื•ืช.
02:42
And immediately starts again.
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ื•ืžื™ื™ื“ ืžืชื—ื™ืœื” ืฉื•ื‘.
02:44
Only now, she's not crying reflex tears but emotional tears.
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ืจืง ืฉืขื›ืฉื™ื•, ื”ื™ื ืœื ื‘ื•ื›ื” ื“ืžืขื•ืช ืจืคืงืก
ืืœื ื“ืžืขื•ืช ืจื’ืฉื™ื•ืช.
02:49
When someone is either too sad or too happy,
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ื›ืฉืžื™ืฉื”ื• ืขืฆื•ื‘ ืื• ืฉืžื— ืžื“ื™,
02:52
it feels like a loss of control,
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ื–ื” ืžืจื’ื™ืฉ ื›ืžื• ืื™ื‘ื•ื“ ืฉืœื™ื˜ื”,
02:54
which can be dangerous.
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ืฉื™ื›ื•ืœ ืœื”ื™ื•ืช ืžืกื•ื›ืŸ.
02:55
So, emotional tears are sent in to stabilize the mood
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ืื–, ื“ืžืขื•ืช ืจื’ืฉื™ื•ืช ื ืฉืœื—ื•ืช
ื›ื“ื™ ืœื™ื™ืฆื‘ ืืช ืžืฆื‘ ื”ืจื•ื—
02:58
as quickly as possible,
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ืžื”ืจ ื›ื›ืœ ื”ืืคืฉืจ,
03:00
along with other physical reactions,
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ื™ื—ื“ ืขื ืชื’ื•ื‘ื•ืช ืคื™ืกื™ื•ืช ืื—ืจื•ืช,
03:02
such as an increased heart rate and slower breathing.
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ื›ืžื• ืขืœื™ื” ื‘ืงืฆื‘ ื”ืœื‘
ื•ื ืฉื™ืžื” ืื™ื˜ื™ืช ื™ื•ืชืจ.
03:05
But scientists still aren't sure
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ืื‘ืœ ืžื“ืขื ื™ื ืœื ื‘ื˜ื•ื—ื™ื
03:07
exactly how or why the tears themselves are helpful.
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ื‘ื“ื™ื•ืง ืื™ืš ืื• ืœืžื” ื”ื“ืžืขื•ืช ืขืฆืžืŸ ืžื•ืขื™ืœื•ืช.
03:11
They may be a social mechanism to elicit sympathy or show submission.
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ื”ืŸ ืื•ืœื™ ืžื ื’ื ื•ืŸ ื—ื‘ืจืชื™
ืœื”ืฉื™ื’ ืกื™ืžืคื˜ื™ื” ืื• ืœื”ืจืื•ืช ื›ื ื™ืขื”.
03:15
But some studies have also found
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ืื‘ืœ ื›ืžื” ืžื—ืงืจื™ื ืžืฆืื• ื’ื
03:17
that emotional tears contain higher levels of stress hormones,
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ืฉื“ืžืขื•ืช ืจื’ืฉื™ื•ืช ืžื›ื™ืœื•ืช ืจืžื•ืช ื’ื‘ื•ื”ื•ืช ื™ื•ืชืจ
ืฉืœ ื”ื•ืจืžื•ื ื™ ืœื—ืฅ,
03:21
such as ACTH and enkephalin,
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ื›ืžื• ACTH ื•ืื ืฆืคืœื™ืŸ,
03:24
an endorphin and natural pain killer.
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ืื ื“ื•ืจืคื™ืŸ ื•ืžืฉื›ืš ื›ืื‘ื™ื ื˜ื‘ืขื™.
03:26
In this case, emotional tears are also directly calming Iris down,
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ื‘ืžืงืจื” ื”ื–ื”, ื“ืžืขื•ืช ืจื’ืฉื™ื•ืช ื’ื ืžืจื’ื™ืขื•ืช ืืช ืื™ืจื™ืก,
03:30
as well as signaling her emotional state to others.
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ื›ืžื• ื’ื ืžื•ื“ื™ืขื•ืช ืขืœ ื”ืžืฆื‘ ื”ืจื’ืฉื™ ืฉืœื” ืœืื—ืจื™ื.
03:33
Sorry things didn't work out with Onion, Iris,
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ืกืœื™ื—ื” ืฉื”ื“ื‘ืจื™ื ืœื ื”ืกืชื“ืจื• ืขื ื‘ืฆืœ ื•ืื™ืจื™ืก,
03:35
but don't worry.
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ืื‘ืœ ืืœ ืชื“ืื’ื•.
03:37
As long as you have all three kinds of tears
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ื›ืœ ืขื•ื“ ื™ืฉ ืœื›ื ืืช ื›ืœ ืฉืœื•ืฉืช ื”ืกื•ื’ื™ื ืฉืœ ื”ื“ืžืขื•ืช
03:39
working to keep you balanced and healthy, it will get better.
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ืขื•ื‘ื“ื™ื ื›ื“ื™ ืœืฉืžื•ืจ ืขืœื™ื›ื ืžืื•ื–ื ื™ื ื•ื‘ืจื™ืื™ื,
ื–ื” ื™ืฉืชืคืจ.
03:42
You'll see.
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ืืชื ืชืจืื•.
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

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