1
00:00:00,000 --> 00:00:00,490


2
00:00:00,490 --> 00:00:03,280
I've done a bunch of videos already on respiration.

3
00:00:03,279 --> 00:00:06,439
I think even before those videos, you had a sense that

4
00:00:06,440 --> 00:00:13,510
we need oxygen and that we release CO2.

5
00:00:13,509 --> 00:00:17,190
And if you watched the videos on respiration, you know that

6
00:00:17,190 --> 00:00:21,490
we need the oxygen in order to metabolize our food, in order

7
00:00:21,489 --> 00:00:25,979
to turn our food into ATPs that can then drive other

8
00:00:25,980 --> 00:00:28,300
types of cellular functions-- or anything that we have to

9
00:00:28,300 --> 00:00:31,030
do; move, or breathe, or think, or everything that we

10
00:00:31,030 --> 00:00:31,480
have to do.

11
00:00:31,480 --> 00:00:35,829
And that through the process of respiration, we break down

12
00:00:35,829 --> 00:00:39,210
those sugars and we release carbon dioxide.

13
00:00:39,210 --> 00:00:42,980
So in this video, what I want to do is take a big step back

14
00:00:42,979 --> 00:00:45,769
and think about how we actually get our oxygen into

15
00:00:45,770 --> 00:00:49,480
our body and how we release it back out into the atmosphere.

16
00:00:49,479 --> 00:00:51,619
Another way to think about it is how we ventilate ourselves.

17
00:00:51,619 --> 00:00:54,250


18
00:00:54,250 --> 00:00:57,020
How do we get the oxygen in, and how do we get the carbon

19
00:00:57,020 --> 00:00:58,200
dioxide out?

20
00:00:58,200 --> 00:01:01,560
And I think any of us could at least start off this video.

21
00:01:01,560 --> 00:01:04,030
It starts off in either our nose or our mouth.

22
00:01:04,030 --> 00:01:07,829
I always have a clogged sinus so I often have to

23
00:01:07,829 --> 00:01:08,719
deal with my mouth.

24
00:01:08,719 --> 00:01:10,109
I sleep with my mouth often.

25
00:01:10,109 --> 00:01:12,349
But it always starts in our nose or our mouths.

26
00:01:12,349 --> 00:01:15,849
Let me draw someone with a nose and a mouth.

27
00:01:15,849 --> 00:01:17,849
So let's say that this is my person.

28
00:01:17,849 --> 00:01:21,864
Maybe his mouth will be open so that he can breathe.

29
00:01:21,864 --> 00:01:25,349


30
00:01:25,349 --> 00:01:28,379
His eyes aren't important, but just so

31
00:01:28,379 --> 00:01:29,799
you know it's a person.

32
00:01:29,799 --> 00:01:32,609
So this is my test subject or the person I'm

33
00:01:32,609 --> 00:01:34,900
going to use to diagram.

34
00:01:34,900 --> 00:01:36,340
That's his ear.

35
00:01:36,340 --> 00:01:41,484
Maybe he has a bit of a-- let's give him some hair.

36
00:01:41,484 --> 00:01:45,209


37
00:01:45,209 --> 00:01:47,789
All of that is irrelevant, but this is our guy.

38
00:01:47,790 --> 00:01:51,200
This is the guy that's going to show us how we take air in

39
00:01:51,200 --> 00:01:54,120
and how we take air out of the body.

40
00:01:54,120 --> 00:01:57,910
So let's go inside of this guy.

41
00:01:57,909 --> 00:02:01,679
I can draw his outside first. Let me see how

42
00:02:01,680 --> 00:02:02,510
well I can do this.

43
00:02:02,510 --> 00:02:04,390
So this is outside the guy.

44
00:02:04,390 --> 00:02:06,439
That doesn't look right.

45
00:02:06,439 --> 00:02:09,419
Let's say the guy looks something like this and he's

46
00:02:09,419 --> 00:02:12,900
got-- this is his shoulders.

47
00:02:12,900 --> 00:02:14,010
That's our guy.

48
00:02:14,009 --> 00:02:14,899
All right.

49
00:02:14,900 --> 00:02:19,200
So in our mouth, we have our oral cavity right there, which

50
00:02:19,199 --> 00:02:21,649
is just the space that our mouth creates.

51
00:02:21,650 --> 00:02:22,770
We have our oral cavity.

52
00:02:22,770 --> 00:02:25,960
I could draw our tongue and all of that and maybe I will.

53
00:02:25,960 --> 00:02:28,055
Maybe I'll draw the tongue.

54
00:02:28,055 --> 00:02:32,020


55
00:02:32,020 --> 00:02:34,780
But you have this space inside of the mouth-- call that the

56
00:02:34,780 --> 00:02:36,030
oral cavity.

57
00:02:36,030 --> 00:02:46,900


58
00:02:46,900 --> 00:02:50,340
Oral for mouth, cavity for space, or hole, or opening.

59
00:02:50,340 --> 00:02:52,700
And then also you have your nostrils and they open up into

60
00:02:52,699 --> 00:02:53,949
a nasal cavity.

61
00:02:53,949 --> 00:02:56,560


62
00:02:56,560 --> 00:02:59,310
So that's another big space just like this.

63
00:02:59,310 --> 00:03:03,800
And we know that they connect at the back of our nose or the

64
00:03:03,800 --> 00:03:05,020
back of our mouth.

65
00:03:05,020 --> 00:03:10,880
And this passage right here where they connect is called

66
00:03:10,879 --> 00:03:12,129
the pharynx.

67
00:03:12,129 --> 00:03:17,180


68
00:03:17,180 --> 00:03:19,640
When your air goes through your nose-- they say breathing

69
00:03:19,639 --> 00:03:21,679
through your nose is better, probably because it gets

70
00:03:21,680 --> 00:03:24,819
filtered by your nose hairs and it gets warmed up and and

71
00:03:24,819 --> 00:03:27,180
what not, but you can breathe through either side.

72
00:03:27,180 --> 00:03:32,900
The air goes in through either your nasal cavity or your oral

73
00:03:32,900 --> 00:03:38,420
cavity and then comes back through your pharynx and then

74
00:03:38,419 --> 00:03:41,219
the pharynx splits into two pipes.

75
00:03:41,219 --> 00:03:44,139
One for-- well, one, air can go down either one, but the

76
00:03:44,139 --> 00:03:45,659
other one is for food.

77
00:03:45,659 --> 00:03:47,699
So your pharynx gets split.

78
00:03:47,699 --> 00:03:51,719
In the back you have your esophagus-- and we'll talk

79
00:03:51,719 --> 00:03:54,289
more about the esophagus in a future video.

80
00:03:54,289 --> 00:03:57,539
In the back you have your esophagus and in the front--

81
00:03:57,539 --> 00:04:00,030
let me draw a little dividing line there.

82
00:04:00,030 --> 00:04:03,370
In the front, maybe this-- let me make it connect like that.

83
00:04:03,370 --> 00:04:04,319
I was using yellow.

84
00:04:04,319 --> 00:04:05,870
I'm going to use yellow to continue and I'm going to use

85
00:04:05,870 --> 00:04:07,730
green for the air.

86
00:04:07,729 --> 00:04:09,525
So it divides just like that.

87
00:04:09,526 --> 00:04:12,350


88
00:04:12,349 --> 00:04:16,550
So behind your air pipe, you have your esophagus.

89
00:04:16,550 --> 00:04:21,470


90
00:04:21,470 --> 00:04:22,720
Let me make that another color.

91
00:04:22,720 --> 00:04:31,280


92
00:04:31,279 --> 00:04:33,029
And then right here is your larynx.

93
00:04:33,029 --> 00:04:37,979


94
00:04:37,980 --> 00:04:40,460
And I'm going to concern ourselves with the larynx.

95
00:04:40,459 --> 00:04:42,439
Esophagus is where your food goes down.

96
00:04:42,439 --> 00:04:44,910
We know that we eat food with our mouth as well.

97
00:04:44,910 --> 00:04:46,710
So this is where we want our food to

98
00:04:46,709 --> 00:04:50,310
go-- down the esophagus.

99
00:04:50,310 --> 00:04:52,699
But the focus of this video is our ventilation.

100
00:04:52,699 --> 00:04:54,599
What do we do with our air?

101
00:04:54,600 --> 00:04:59,260
So I'm going to focus as the air goes through our larynx.

102
00:04:59,259 --> 00:05:02,029
And the larynx is also our voicebox.

103
00:05:02,029 --> 00:05:05,459
So as you hear me talking right now, there are these

104
00:05:05,459 --> 00:05:08,359
little things right about here that are vibrating at just the

105
00:05:08,360 --> 00:05:10,900
right frequencies and I'm able to shape the sound with my

106
00:05:10,899 --> 00:05:12,329
mouth to make this video.

107
00:05:12,329 --> 00:05:14,339
So that's also your voicebox, but I won't focus

108
00:05:14,339 --> 00:05:15,179
on that right now.

109
00:05:15,180 --> 00:05:17,769
It's called a voicebox because of this whole anatomical

110
00:05:17,769 --> 00:05:19,579
structure that looks something like that.

111
00:05:19,579 --> 00:05:22,609
But then after the air passes through the larynx-- this is

112
00:05:22,610 --> 00:05:31,580
on the way in-- it goes to the trachea, which is essentially

113
00:05:31,579 --> 00:05:32,829
just the pipe for air.

114
00:05:32,829 --> 00:05:35,169
The esophagus is the pipe for food.

115
00:05:35,170 --> 00:05:36,420
Let me write this down.

116
00:05:36,420 --> 00:05:40,960


117
00:05:40,959 --> 00:05:43,279
And then from the trachea-- and the trachea is actually a

118
00:05:43,279 --> 00:05:44,589
reasonably rigid structure.

119
00:05:44,589 --> 00:05:46,779
It has cartilage around it and it makes

120
00:05:46,779 --> 00:05:47,969
sense that it has cartilage.

121
00:05:47,970 --> 00:05:51,290
You don't want-- you can imagine a hose-- if it bent a

122
00:05:51,290 --> 00:05:53,240
lot, you wouldn't be able to get a lot of water through it,

123
00:05:53,240 --> 00:05:54,310
or a lot of air through it.

124
00:05:54,310 --> 00:05:56,530
So you don't want this thing to bend a lot.

125
00:05:56,529 --> 00:05:58,629
So that's why it needs to have some rigidity-- so that's why

126
00:05:58,629 --> 00:05:59,930
it has cartilage around it.

127
00:05:59,930 --> 00:06:06,090
And then it splits into two tubes-- and I think you know

128
00:06:06,089 --> 00:06:08,269
where these two tubes are going to.

129
00:06:08,269 --> 00:06:10,589
And I'm not drawing this in super detail.

130
00:06:10,589 --> 00:06:13,409
I just want you to get the idea of them, but these two

131
00:06:13,410 --> 00:06:15,770
tubes are the bronchi-- or each one is a bronchus.

132
00:06:15,769 --> 00:06:21,849


133
00:06:21,850 --> 00:06:24,550
And they also have cartilage, so they're fairly rigid, but

134
00:06:24,550 --> 00:06:26,480
the bronchi keep splitting.

135
00:06:26,480 --> 00:06:31,140
They keep splitting into smaller and smaller tubes just

136
00:06:31,139 --> 00:06:33,319
like that and at some point, they stop having cartilage.

137
00:06:33,319 --> 00:06:35,689
They stop being reasonably rigid, but they

138
00:06:35,689 --> 00:06:37,290
keep splitting off.

139
00:06:37,290 --> 00:06:39,030
So I'll just draw them as these little lines.

140
00:06:39,029 --> 00:06:42,529
At some point they become such thin things.

141
00:06:42,529 --> 00:06:44,169
They just keep splitting off.

142
00:06:44,170 --> 00:06:47,560
So the air just keeps splitting off and spread and

143
00:06:47,560 --> 00:06:49,100
goes down the different paths.

144
00:06:49,100 --> 00:06:52,400
And when the bronchi no longer have cartilage around them,

145
00:06:52,399 --> 00:06:53,489
they're no longer rigid.

146
00:06:53,490 --> 00:06:55,689
The first of those are called-- or actually all the

147
00:06:55,689 --> 00:06:59,480
tubes after that point are called bronchioles.

148
00:06:59,480 --> 00:07:00,629
These are bronchioles.

149
00:07:00,629 --> 00:07:03,629
So for example, that we could call a bronchiole.

150
00:07:03,629 --> 00:07:05,225
And there's nothing fancy here.

151
00:07:05,225 --> 00:07:07,379
It's just a pipe that just gets thinner

152
00:07:07,379 --> 00:07:08,110
and thinner and thinner.

153
00:07:08,110 --> 00:07:10,920
We've labeled the different parts of the pipes different

154
00:07:10,920 --> 00:07:13,379
things, but the idea is, let's take it through our mouth or

155
00:07:13,379 --> 00:07:16,019
our nose and we just keep dividing and keep dividing

156
00:07:16,019 --> 00:07:19,310
this main division into two different paths that takes us

157
00:07:19,310 --> 00:07:21,550
into each of our lungs.

158
00:07:21,550 --> 00:07:24,009
Let me draw this guy's lungs here.

159
00:07:24,009 --> 00:07:33,259


160
00:07:33,259 --> 00:07:36,589
And these bronchi-- or the bronchi split into the lungs--

161
00:07:36,589 --> 00:07:39,719
the bronchioles are in the lungs and eventually the

162
00:07:39,720 --> 00:07:41,660
bronchioles terminate.

163
00:07:41,660 --> 00:07:43,020
And this is where it gets interesting.

164
00:07:43,019 --> 00:07:45,500
They keep dividing smaller and smaller, thinner and thinner

165
00:07:45,500 --> 00:07:52,110
and thinner, into these little air sacs, just like that.

166
00:07:52,110 --> 00:07:55,770
At the end of every super small bronchiole are these

167
00:07:55,769 --> 00:07:59,500
little air sacs-- super small air sacs-- and I'm going to

168
00:07:59,500 --> 00:08:02,060
talk about these air sacs in a second.

169
00:08:02,060 --> 00:08:03,310
And these are called alveoli.

170
00:08:03,310 --> 00:08:08,899


171
00:08:08,899 --> 00:08:10,699
So I've used a lot of fancy words, but the

172
00:08:10,699 --> 00:08:11,860
general idea is simple.

173
00:08:11,860 --> 00:08:13,050
Air comes in through a pipe.

174
00:08:13,050 --> 00:08:15,020
The pipe gets thinner and thinner and thinner and they

175
00:08:15,019 --> 00:08:16,759
end up at these little air sacs.

176
00:08:16,759 --> 00:08:20,449
And you're saying, well, how does that get the

177
00:08:20,449 --> 00:08:22,930
oxygen into my system?

178
00:08:22,930 --> 00:08:26,459
Well, the key here is that these air sacs are super small

179
00:08:26,459 --> 00:08:30,949
and have very, very, very thin walls-- or

180
00:08:30,949 --> 00:08:32,058
I guess thin membranes.

181
00:08:32,058 --> 00:08:33,699
So let me zoom in.

182
00:08:33,700 --> 00:08:36,740
So if I were to zoom in on one of these alveoli-- and just to

183
00:08:36,740 --> 00:08:39,950
give you an idea, these are super duper duper small.

184
00:08:39,950 --> 00:08:43,799
I've drawn them fairly large here, but each alveoli-- let

185
00:08:43,798 --> 00:08:45,929
me draw a little bit bigger.

186
00:08:45,929 --> 00:08:48,779
Let me draw these air sacs.

187
00:08:48,779 --> 00:08:50,839
So you have these air sacs like this.

188
00:08:50,840 --> 00:08:54,030


189
00:08:54,029 --> 00:08:56,289
And then you have a bronchiole that's

190
00:08:56,289 --> 00:08:57,599
terminating in that air sac.

191
00:08:57,600 --> 00:09:00,320
Maybe a bronchiole is terminating in another air sac

192
00:09:00,320 --> 00:09:04,820
just like that-- another set of air sacs just like that.

193
00:09:04,820 --> 00:09:10,300
Each of these are only 200 to 300 microns in diameter.

194
00:09:10,299 --> 00:09:13,529
So that distance right there-- let me switch colors-- that

195
00:09:13,529 --> 00:09:18,720
distance right there is 200 to 300 microns.

196
00:09:18,720 --> 00:09:22,050
And in case you don't know what a micron is, a micron is

197
00:09:22,049 --> 00:09:25,199
a millionth of a meter-- or you can view it as a

198
00:09:25,200 --> 00:09:26,820
thousandth of a millimeter.

199
00:09:26,820 --> 00:09:30,340
So this is 200 thousandths of a millimeter.

200
00:09:30,340 --> 00:09:32,889
Or you can think of them as-- and this is actually a very

201
00:09:32,889 --> 00:09:38,730
easy way to visualize it-- this is about one fifth of a

202
00:09:38,730 --> 00:09:40,920
millimeter.

203
00:09:40,919 --> 00:09:42,789
So if I actually try to draw it on the screen-- if you made

204
00:09:42,789 --> 00:09:47,599
this full screen, a millimeter is about that far.

205
00:09:47,600 --> 00:09:48,690
Maybe a little farther than that.

206
00:09:48,690 --> 00:09:50,130
Maybe about that far.

207
00:09:50,129 --> 00:09:52,529
So imagine a fifth of that and that's what we're talking

208
00:09:52,529 --> 00:09:54,579
about the diameter of one of these things.

209
00:09:54,580 --> 00:09:56,470
And just to put it in the whole scheme relative to

210
00:09:56,470 --> 00:09:58,330
cells, the average cell in the human

211
00:09:58,330 --> 00:10:00,759
body is about 10 microns.

212
00:10:00,759 --> 00:10:04,450
So this is only about 20 or 30 cells in diameter or relative

213
00:10:04,450 --> 00:10:06,600
to the average cell in the human body.

214
00:10:06,600 --> 00:10:08,360
So these have a super thin membrane.

215
00:10:08,360 --> 00:10:12,180


216
00:10:12,179 --> 00:10:15,479
If you view them as balloons, the balloon is very thin--

217
00:10:15,480 --> 00:10:20,259
pretty much one cell thick and they're connected to the

218
00:10:20,259 --> 00:10:22,409
bloodflow-- or actually, a better way to think about is

219
00:10:22,409 --> 00:10:26,539
that our circulatory system passes right next to each of

220
00:10:26,539 --> 00:10:27,099
these things.

221
00:10:27,100 --> 00:10:32,580
So you have blood vessels that come from the heart and they

222
00:10:32,580 --> 00:10:33,860
want to be oxygenated.

223
00:10:33,860 --> 00:10:37,810
In general, the blood vessels that don't have oxygen-- and

224
00:10:37,809 --> 00:10:39,899
I'm going to do this in a lot more detail when I make the

225
00:10:39,899 --> 00:10:43,250
videos about the heart and our circulation system-- the blood

226
00:10:43,250 --> 00:10:45,570
vessels that don't have oxygen-- de-oxygenated blood

227
00:10:45,570 --> 00:10:46,420
is a little bit darker.

228
00:10:46,419 --> 00:10:47,769
It looks a little bit purplish.

229
00:10:47,769 --> 00:10:49,399
So I'll draw it as blue.

230
00:10:49,399 --> 00:10:55,889
So these are vessels that are coming from the heart.

231
00:10:55,889 --> 00:11:00,059
So this blood right here has no oxygen in it or it's been

232
00:11:00,059 --> 00:11:02,649
de-oxygenated or it has very little oxygen in it.

233
00:11:02,649 --> 00:11:06,519
And the word for the blood vessels that comes from the

234
00:11:06,519 --> 00:11:08,009
heart are arteries.

235
00:11:08,009 --> 00:11:08,759
Let me write that down.

236
00:11:08,759 --> 00:11:11,289
I'll review that again when we cover it in the heart.

237
00:11:11,289 --> 00:11:21,589
So arteries are blood vessels from the heart.

238
00:11:21,590 --> 00:11:24,220


239
00:11:24,220 --> 00:11:26,769
And you've probably heard of arteries.

240
00:11:26,769 --> 00:11:29,189
Vessels that go to the heart are called veins.

241
00:11:29,190 --> 00:11:36,010


242
00:11:36,009 --> 00:11:39,159
This is really important to keep in mind because later on,

243
00:11:39,159 --> 00:11:42,269
you're going to see that arteries don't always carry

244
00:11:42,269 --> 00:11:45,100
oxygen or they're always not de-oxygenated and veins always

245
00:11:45,100 --> 00:11:45,899
aren't one way or the other.

246
00:11:45,899 --> 00:11:47,519
We're going to go into a lot more detail when we actually

247
00:11:47,519 --> 00:11:49,779
cover the heart and the circulatory system, but just

248
00:11:49,779 --> 00:11:51,629
remember, arteries go away.

249
00:11:51,629 --> 00:11:53,509
Veins go to the heart.

250
00:11:53,509 --> 00:11:58,610
So here, these are arteries going away from the heart to

251
00:11:58,610 --> 00:12:03,019
the lungs, to the alveoli because they want the blood

252
00:12:03,019 --> 00:12:05,309
that's traveling in them to get oxygen.

253
00:12:05,309 --> 00:12:09,719
So what's going to happen is that the air is flowing

254
00:12:09,720 --> 00:12:16,060
through the bronchioles and circulating around the

255
00:12:16,059 --> 00:12:20,649
alveoli, filling the alveoli-- and as they fill the alveoli,

256
00:12:20,649 --> 00:12:27,679
the little molecules of oxygen are allowed to cross the

257
00:12:27,679 --> 00:12:30,219
membrane of the alveoli and essentially be

258
00:12:30,220 --> 00:12:31,529
absorbed into the blood.

259
00:12:31,529 --> 00:12:33,850
I'll do a lot more on that when we talk about hemoglobin

260
00:12:33,850 --> 00:12:35,740
and red blood cells, but you just have to realize that

261
00:12:35,740 --> 00:12:38,919
there's just a lot of capillaries.

262
00:12:38,919 --> 00:12:41,809
Capillaries are just super small blood vessels that allow

263
00:12:41,809 --> 00:12:44,849
air to pass-- essentially oxygen and carbon dioxide

264
00:12:44,850 --> 00:12:46,560
molecules to pass between them.

265
00:12:46,559 --> 00:12:48,579
These have a lot of capillaries on them that allow

266
00:12:48,580 --> 00:12:51,450
the exchange of gases.

267
00:12:51,450 --> 00:12:56,470
So the oxygen can go into this blood and so once the oxygen--

268
00:12:56,470 --> 00:13:00,310
so this is the vessel that's coming from the heart and then

269
00:13:00,309 --> 00:13:01,099
it's just a tube.

270
00:13:01,100 --> 00:13:03,710
So then once it gets the oxygen, it's going to go back

271
00:13:03,710 --> 00:13:04,960
to the heart.

272
00:13:04,960 --> 00:13:09,889


273
00:13:09,889 --> 00:13:13,789
And so essentially this is the point where this vessel, this

274
00:13:13,789 --> 00:13:16,839
pipe, part of our circulatory system, goes from being an

275
00:13:16,840 --> 00:13:19,745
artery-- because it's coming from the heart-- to a vein

276
00:13:19,745 --> 00:13:22,320
because it's going back to the heart.

277
00:13:22,320 --> 00:13:26,010
And there's a special word for these arteries and veins.

278
00:13:26,009 --> 00:13:28,899
They're called pulmonary arteries and veins.

279
00:13:28,899 --> 00:13:34,980
So going away from the heart to the lungs, to the alveoli,

280
00:13:34,980 --> 00:13:40,840
these are the pulmonary arteries.

281
00:13:40,840 --> 00:13:44,774
And going back to the heart are the pulmonary veins.

282
00:13:44,774 --> 00:13:49,799


283
00:13:49,799 --> 00:13:53,089
Now you're saying, Sal, what does pulmonary mean?

284
00:13:53,090 --> 00:13:55,920
Well, pulmo comes from the Latin for the lungs.

285
00:13:55,919 --> 00:13:59,089
It literally means the arteries that are of the lungs

286
00:13:59,090 --> 00:14:01,379
or that go to the lungs and the veins that

287
00:14:01,379 --> 00:14:02,299
come from the lungs.

288
00:14:02,299 --> 00:14:04,839
So anytime people talk about pulmonary anything, they're

289
00:14:04,840 --> 00:14:09,200
talking about our lungs-- or maybe something related to how

290
00:14:09,200 --> 00:14:09,770
we breathe.

291
00:14:09,769 --> 00:14:13,199
So it's a good word to know.

292
00:14:13,200 --> 00:14:19,300
So anyway, you have your oxygen coming in through your

293
00:14:19,299 --> 00:14:22,669
mouth or your nose, through the pharynx-- it could fill

294
00:14:22,669 --> 00:14:23,199
your stomach.

295
00:14:23,200 --> 00:14:25,550
We can blow up our stomach like a balloon, but that

296
00:14:25,549 --> 00:14:29,149
doesn't help us actually get oxygen to our blood stream.

297
00:14:29,149 --> 00:14:32,990
But the oxygen will come through our larynx, into our

298
00:14:32,990 --> 00:14:36,269
trachea, through the bronchi, eventually in bronchioles,

299
00:14:36,269 --> 00:14:40,120
ending up in alveoli and being able to be absorbed into what

300
00:14:40,120 --> 00:14:42,570
where the arteries, but then we're going to go back and

301
00:14:42,570 --> 00:14:44,490
then essentially oxygenate the blood.

302
00:14:44,490 --> 00:14:50,139
The red blood cells become red once the hemoglobin becomes

303
00:14:50,139 --> 00:14:53,980
very red or scarlet once it actually has the oxygen and

304
00:14:53,980 --> 00:14:55,300
then we go back.

305
00:14:55,299 --> 00:14:58,139
But at the same time, this isn't just about getting

306
00:14:58,139 --> 00:15:01,850
oxygen into our arteries or onto the hemoglobin.

307
00:15:01,850 --> 00:15:05,110
It's also about releasing carbon dioxide.

308
00:15:05,110 --> 00:15:10,610
So these blue arteries coming from the lungs are also going

309
00:15:10,610 --> 00:15:14,730
to release carbon dioxide into the alveoli.

310
00:15:14,730 --> 00:15:16,560
And these will be exhaled.

311
00:15:16,559 --> 00:15:18,359
So we have oxygen coming in.

312
00:15:18,360 --> 00:15:21,970


313
00:15:21,970 --> 00:15:24,110
Other things will be coming in, but the O2 is what gets

314
00:15:24,110 --> 00:15:25,789
absorbed in the alveoli.

315
00:15:25,789 --> 00:15:30,679
And then when we breathe out, we're going to have carbon

316
00:15:30,679 --> 00:15:33,849
dioxide that was in our blood, but then it gets absorbed into

317
00:15:33,850 --> 00:15:35,840
the alveoli and they get squeezed out.

318
00:15:35,840 --> 00:15:37,685
I'm going to tell you in a second how it gets squeezed.

319
00:15:37,684 --> 00:15:43,319


320
00:15:43,320 --> 00:15:46,120
It's actually that squeezing out that actually-- when the

321
00:15:46,120 --> 00:15:51,159
air goes back out, it can vibrate my vocal cords and

322
00:15:51,159 --> 00:15:53,209
it'll allow me to talk, but I'm not going to go into too

323
00:15:53,210 --> 00:15:54,620
much detail about that.

324
00:15:54,620 --> 00:15:58,200
So the last thing to consider about this whole pulmonary

325
00:15:58,200 --> 00:16:04,360
system or about our lungs is, how does it force the air in

326
00:16:04,360 --> 00:16:06,690
and how does it force the air out?

327
00:16:06,690 --> 00:16:09,660
And the way it's done is really kind of like a-- you

328
00:16:09,659 --> 00:16:12,699
could imagine it's kind of a pump or a balloon-- is that we

329
00:16:12,700 --> 00:16:15,680
have this huge layer of flat muscles.

330
00:16:15,679 --> 00:16:17,169
Let me pick a good color here.

331
00:16:17,169 --> 00:16:25,860


332
00:16:25,860 --> 00:16:27,399
Right below the lungs-- and this is

333
00:16:27,399 --> 00:16:28,649
called a thoracic diaphragm.

334
00:16:28,649 --> 00:16:38,319


335
00:16:38,320 --> 00:16:41,280
And so when it's relaxed, it kind of has this arch shape,

336
00:16:41,279 --> 00:16:43,699
and so the lungs are kind of squeezed in.

337
00:16:43,700 --> 00:16:45,440
They don't have a lot of volume.

338
00:16:45,440 --> 00:16:49,380
But when I essentially breathe in, what's happening is this

339
00:16:49,379 --> 00:16:52,169
thoracic diaphragm is contracted and when it's

340
00:16:52,169 --> 00:16:55,949
contracted, it gets shorter, but more importantly, it opens

341
00:16:55,950 --> 00:17:00,440
up the space where my lungs are.

342
00:17:00,440 --> 00:17:02,330
So my lungs can fill up that space.

343
00:17:02,330 --> 00:17:04,920
So what it does is, it essentially-- it's like

344
00:17:04,920 --> 00:17:07,420
pulling a balloon larger, making the

345
00:17:07,420 --> 00:17:10,064
volume of my lungs larger.

346
00:17:10,064 --> 00:17:13,310
And when you make the volume of something larger-- so the

347
00:17:13,309 --> 00:17:16,000
lungs will become larger as my thoracic diaphragm is

348
00:17:16,000 --> 00:17:18,630
contracted and it kind of arches down, creates more

349
00:17:18,630 --> 00:17:22,150
space-- and as the volume of something becomes larger, the

350
00:17:22,150 --> 00:17:24,140
pressure inside of them goes down.

351
00:17:24,140 --> 00:17:26,420
If you remember from physics, the pressure

352
00:17:26,420 --> 00:17:27,720
times volume is a constant.

353
00:17:27,720 --> 00:17:31,279


354
00:17:31,279 --> 00:17:39,049
So when we breathe in, our brain is essentially telling

355
00:17:39,049 --> 00:17:40,299
our diaphragm to contract.

356
00:17:40,299 --> 00:17:48,549


357
00:17:48,549 --> 00:17:51,125
We have more space around our lungs.

358
00:17:51,125 --> 00:17:56,390
Our lungs expand to fill the space.

359
00:17:56,390 --> 00:17:59,870
We have less pressure here than we have outside-- or you

360
00:17:59,869 --> 00:18:01,539
can view it as negative pressure.

361
00:18:01,539 --> 00:18:04,440
So air always wants to go from high pressure to low pressure

362
00:18:04,440 --> 00:18:07,059
and so air is going to flow into our lungs.

363
00:18:07,059 --> 00:18:10,710
And hopefully there'll be some oxygen there that can then

364
00:18:10,710 --> 00:18:13,529
essentially go into our alveoli and end up in our

365
00:18:13,529 --> 00:18:17,190
arteries and then go back in the veins as oxygen attached

366
00:18:17,190 --> 00:18:17,820
to hemoglobin.

367
00:18:17,819 --> 00:18:19,529
I'll talk more about that in detail.

368
00:18:19,529 --> 00:18:21,960
And then when we stop contracting the diaphragm, it

369
00:18:21,960 --> 00:18:23,980
goes back to this arched position.

370
00:18:23,980 --> 00:18:25,019
It contracts.

371
00:18:25,019 --> 00:18:26,549
It's kind of like a rubber band.

372
00:18:26,549 --> 00:18:30,480
It contracts back the lungs and it essentially expels the

373
00:18:30,480 --> 00:18:33,779
air back and now that air's going to have a lot more

374
00:18:33,779 --> 00:18:35,119
carbon dioxide.

375
00:18:35,119 --> 00:18:39,129
And just to get a sense of-- I can look at my lungs-- I can't

376
00:18:39,130 --> 00:18:42,130
look at them, but they don't seem too large.

377
00:18:42,130 --> 00:18:45,350
How do I get enough oxygen in them-- and the key is, is that

378
00:18:45,349 --> 00:18:52,089
because of this branching process and the alveoli, the

379
00:18:52,089 --> 00:18:55,919
inside surface area of the lungs are actually much larger

380
00:18:55,920 --> 00:18:59,310
than you can imagine-- or actually than I could have

381
00:18:59,309 --> 00:19:01,829
imagined had someone not told me.

382
00:19:01,829 --> 00:19:04,089
So it actually turns out-- I looked it up-- the internal

383
00:19:04,089 --> 00:19:08,649
surface area of your alveoli-- so the total surface area

384
00:19:08,650 --> 00:19:11,470
where the oxygen can be absorbed in or the carbon

385
00:19:11,470 --> 00:19:13,950
dioxide can be absorbed out from the blood-- it's actually

386
00:19:13,950 --> 00:19:18,610
75 square meters.

387
00:19:18,609 --> 00:19:19,909
That's meters, not feet.

388
00:19:19,910 --> 00:19:22,470


389
00:19:22,470 --> 00:19:24,730
If you think about it, that's like a-- imagine some type of

390
00:19:24,730 --> 00:19:26,309
a tarp or a field.

391
00:19:26,309 --> 00:19:29,929
That's almost nine by nine meters.

392
00:19:29,930 --> 00:19:36,340
That's almost 27 by 27 square feet.

393
00:19:36,339 --> 00:19:38,529
That's the size of some people's backyards.

394
00:19:38,529 --> 00:19:41,139
That's how much surface air you have inside of your lungs.

395
00:19:41,140 --> 00:19:42,240
It's all folded up.

396
00:19:42,240 --> 00:19:45,309
That's how it gets jammed into what look like relatively

397
00:19:45,309 --> 00:19:46,220
small lungs.

398
00:19:46,220 --> 00:19:48,410
But that's what gives us enough surface area for enough

399
00:19:48,410 --> 00:19:51,680
of the air, enough of the oxygen, to cross the alveoli

400
00:19:51,680 --> 00:19:54,980
membrane into our blood system and enough of the carbon

401
00:19:54,980 --> 00:19:56,559
dioxide to go back in.

402
00:19:56,559 --> 00:19:59,369
And just to have a sense of how many alveoli we had-- I

403
00:19:59,369 --> 00:20:02,239
told you that they're very small-- we actually have 300

404
00:20:02,240 --> 00:20:04,410
million in each lung.

405
00:20:04,410 --> 00:20:09,350
In each lung, we have 300 million alveoli.

406
00:20:09,349 --> 00:20:12,019
So anyway, hopefully that gives you a decent sense of

407
00:20:12,019 --> 00:20:16,230
how we at least get oxygen into our blood system and

408
00:20:16,230 --> 00:20:17,640
carbon dioxide out of it.

409
00:20:17,640 --> 00:20:20,200
In the next video, I'll talk more about our actual

410
00:20:20,200 --> 00:20:26,519
circulatory system and how we get the oxygen from the lungs

411
00:20:26,519 --> 00:20:28,240
to the rest of the body and how do we get the carbon

412
00:20:28,240 --> 00:20:31,640
dioxide from the rest of the body into the lungs?

413
00:20:31,640 --> 00:20:32,097