Circulatory system and the heart

WEBVTT
Kind: captions
Language: en

00:00:00.520 --> 00:00:03.950
Where I left off in the last
video, we talked about how the

00:00:03.950 --> 00:00:07.440
hemoglobin in red blood cells
is what sops up all of the

00:00:07.440 --> 00:00:11.440
oxygen so that it increases the
diffusion gradient-- or it

00:00:11.440 --> 00:00:14.800
increases the incentive, we
could say, for the oxygen to

00:00:14.800 --> 00:00:15.760
go across the membrane.

00:00:15.760 --> 00:00:18.390
We know that the oxygen
molecules don't know that

00:00:18.390 --> 00:00:21.185
there's less oxygen here, but
if you watch the video on

00:00:21.185 --> 00:00:23.170
diffusion you know how
that process happens.

00:00:23.170 --> 00:00:25.840
If there's less concentration
here than there, the oxygen

00:00:25.840 --> 00:00:29.070
will diffuse across the membrane
and there's less

00:00:29.070 --> 00:00:33.010
inside the plasma because the
hemoglobin is sucking it all

00:00:33.010 --> 00:00:34.510
up like a sponge.

00:00:34.510 --> 00:00:38.060
Now, one interesting question
is, why does the hemoglobin

00:00:38.060 --> 00:00:42.570
even have to reside within
the red blood cells?

00:00:42.570 --> 00:00:45.680
Why aren't hemoglobin proteins
just freely floating in the

00:00:45.680 --> 00:00:46.650
blood plasma?

00:00:46.650 --> 00:00:48.060
That seems more efficient.

00:00:48.060 --> 00:00:51.020
You don't have to have things
crossing through, in and out

00:00:51.020 --> 00:00:53.220
of, these red blood
cell membranes.

00:00:53.220 --> 00:00:55.380
You wouldn't have to make
red blood cells.

00:00:55.380 --> 00:00:58.570
What's the use of having these
containers of hemoglobin?

00:00:58.570 --> 00:01:00.920
It's actually a very
interesting idea.

00:01:00.920 --> 00:01:04.519
If you had all of the hemoglobin
sitting in your

00:01:04.519 --> 00:01:06.960
blood plasma, it would
actually hurt

00:01:06.960 --> 00:01:08.450
the flow of the blood.

00:01:08.450 --> 00:01:11.500
The blood would become more
viscous or more thick.

00:01:11.500 --> 00:01:13.430
I don't want to say like syrup,
but it would become

00:01:13.430 --> 00:01:16.520
thicker than blood is right
now-- and by packaging the

00:01:16.520 --> 00:01:19.700
hemoglobin inside these
containers, inside the red

00:01:19.700 --> 00:01:22.270
blood cells, what it allows
the blood to do

00:01:22.270 --> 00:01:23.800
is flow a lot better.

00:01:23.800 --> 00:01:26.610
Imagine if you wanted to
put syrup in water.

00:01:26.610 --> 00:01:30.890
If you just put syrup
straight into water,

00:01:30.890 --> 00:01:31.650
what's going to happen?

00:01:31.650 --> 00:01:34.100
The water's going to become a
little syrupy, a little bit

00:01:34.100 --> 00:01:36.510
more viscous and not
flow as well.

00:01:36.510 --> 00:01:37.930
So what's the solution
if you wanted to

00:01:37.930 --> 00:01:40.370
transport syrup in water?

00:01:40.370 --> 00:01:43.940
Well, you could put the syrup
inside little containers or

00:01:43.940 --> 00:01:47.140
inside little beads and then
let the beads flow in the

00:01:47.140 --> 00:01:49.540
water and then the water
wouldn't be all gooey-- and

00:01:49.540 --> 00:01:52.520
that's exactly what's happening
inside of our blood.

00:01:52.520 --> 00:01:54.980
Instead of having the hemoglobin
sit in the plasma

00:01:54.980 --> 00:01:58.440
and make it gooey, it sits
inside these beads that we

00:01:58.440 --> 00:02:02.640
call red blood cells that allows
the flow to still be

00:02:02.640 --> 00:02:04.420
non-viscous.

00:02:04.420 --> 00:02:08.800
So I've been all zoomed in here
on the alveolus and these

00:02:08.800 --> 00:02:12.000
capillaries, these pulmonary
capillaries-- let's zoom out a

00:02:12.000 --> 00:02:15.920
little bit-- or zoom out a lot--
just to understand, how

00:02:15.920 --> 00:02:17.130
is the blood flowing?

00:02:17.130 --> 00:02:19.790
And get a better understanding
of pulmonary arteries and

00:02:19.790 --> 00:02:22.920
veins relative to the other
arteries and veins

00:02:22.920 --> 00:02:25.140
that are in the body.

00:02:25.140 --> 00:02:29.740
So here-- I copied this from
Wikipedia, this diagram of the

00:02:29.740 --> 00:02:32.810
human circulatory system--
and here in the back

00:02:32.810 --> 00:02:34.310
you can see the lungs.

00:02:34.310 --> 00:02:38.220
Let me do it in a
nice dark color.

00:02:38.220 --> 00:02:39.880
So we have our lungs here.

00:02:44.600 --> 00:02:46.890
You can see the heart is sitting
right in the middle.

00:02:46.890 --> 00:02:49.110
And what we learned in the last
few videos is that we

00:02:49.110 --> 00:02:51.260
have our little alveoli
and our lungs.

00:02:51.260 --> 00:02:54.780
Remember, we get to them from
our bronchioles, which are

00:02:54.780 --> 00:02:57.190
branching off of the bronchi,
which branch off of the

00:02:57.190 --> 00:02:59.590
trachea, which connects to our
larynx, which connects to our

00:02:59.590 --> 00:03:01.900
pharynx, which connects
to our mouth and nose.

00:03:01.900 --> 00:03:07.350
But anyway, we have our little
alveoli right there and then

00:03:07.350 --> 00:03:09.880
we have the capillaries.

00:03:09.880 --> 00:03:15.450
So when we go away from the
heart-- and we're going to

00:03:15.450 --> 00:03:17.910
delve a little bit into the
heart in this video as well--

00:03:17.910 --> 00:03:20.140
so when blood travels away
from the heart, it's

00:03:20.140 --> 00:03:21.130
de-oxygenated.

00:03:21.130 --> 00:03:22.230
It's this blue color.

00:03:22.230 --> 00:03:24.960
So this right here is blood.

00:03:24.960 --> 00:03:27.050
This right here is blood
traveling away from the heart.

00:03:27.050 --> 00:03:30.310
It's going behind these
two tubes right there.

00:03:30.310 --> 00:03:33.230
So this is the blood going
away from the heart.

00:03:33.230 --> 00:03:38.250
So this blue that I've been
highlighting just now, these

00:03:38.250 --> 00:03:43.620
are the pulmonary arteries and
then they keep splitting into

00:03:43.620 --> 00:03:45.900
arterials and all of that
and eventually we're in

00:03:45.900 --> 00:03:48.600
capillaries-- super,
super small tubes.

00:03:48.600 --> 00:03:52.690
They run right past the alveoli
and then they become

00:03:52.690 --> 00:03:58.270
oxygenated and now we're going
back to the heart.

00:03:58.270 --> 00:04:00.730
So we're talking about
pulmonary veins.

00:04:00.730 --> 00:04:02.080
So we go back to the heart.

00:04:02.080 --> 00:04:05.590
So these capillaries-- in the
capillaries we get oxygen.

00:04:05.590 --> 00:04:07.600
Now we're going to go
back to the heart.

00:04:07.600 --> 00:04:11.090
Hope you can see
what I'm doing.

00:04:11.090 --> 00:04:15.450
And we're going to enter
the heart on this side.

00:04:15.450 --> 00:04:16.709
You actually can't even
see where we're

00:04:16.709 --> 00:04:17.290
entering the heart.

00:04:17.290 --> 00:04:19.050
We're going to enter the heart
right over here-- and I'm

00:04:19.050 --> 00:04:20.709
going to go into more
detail on that.

00:04:20.709 --> 00:04:23.040
Now we have oxygenated blood.

00:04:23.040 --> 00:04:23.850
It's red.

00:04:23.850 --> 00:04:26.650
And then that gets pumped out
to the rest of the body.

00:04:26.650 --> 00:04:30.480
Now this is the interesting
thing.

00:04:30.480 --> 00:04:33.060
When we're talking about
pulmonary arteries and veins--

00:04:33.060 --> 00:04:35.170
remember, the pulmonary
artery was blue.

00:04:35.170 --> 00:04:39.240
As we go away from the heart,
we have de-oxygenated blood,

00:04:39.240 --> 00:04:40.610
but it's still an artery.

00:04:40.610 --> 00:04:44.070
Then as we go towards the heart
from the lungs, we have

00:04:44.070 --> 00:04:45.400
a vein, but it's oxygenated.

00:05:12.160 --> 00:05:14.990
So that's this little loop here
that we start and I'm

00:05:14.990 --> 00:05:17.760
going to keep going over the
circulation pattern because

00:05:17.760 --> 00:05:19.560
the heart can get a little
confusing, especially because

00:05:19.560 --> 00:05:22.270
of its three-dimensional
nature.

00:05:22.270 --> 00:05:27.010
But what we have is, the heart
pumps de-oxygenated blood from

00:05:27.010 --> 00:05:28.090
the right ventricle.

00:05:28.090 --> 00:05:29.500
You're saying, hey, why is
it the right ventricle?

00:05:29.500 --> 00:05:31.600
That looks like the left side of
the drawing, but it's this

00:05:31.600 --> 00:05:33.590
dude's right-hand side, right?

00:05:33.590 --> 00:05:37.680
This is this guy's right hand.

00:05:37.680 --> 00:05:39.100
And this is this dude's
left hand.

00:05:39.100 --> 00:05:40.570
He's looking at us, right?

00:05:40.570 --> 00:05:41.790
We don't care about
our right or left.

00:05:41.790 --> 00:05:43.650
We care about this guy's
right and left.

00:05:43.650 --> 00:05:44.530
And he's looking at us.

00:05:44.530 --> 00:05:47.210
He's got some eyeballs and
he's looking at us.

00:05:47.210 --> 00:05:48.790
So this is his right
ventricle.

00:05:48.790 --> 00:05:51.060
Actually, let me just start
off with the whole cycle.

00:05:51.060 --> 00:05:54.110
So we have de-oxygenated blood
coming from the rest of the

00:05:54.110 --> 00:05:55.360
body, right?

00:06:00.060 --> 00:06:04.220
The name for this big pipe is
called the inferior vena

00:06:04.220 --> 00:06:07.310
cava-- inferior because
it's coming up below.

00:06:07.310 --> 00:06:09.680
Actually, you have blood coming
up from the arms and

00:06:09.680 --> 00:06:11.080
the head up here.

00:06:11.080 --> 00:06:19.620
They're both meeting right here,
in the right atrium.

00:06:19.620 --> 00:06:20.950
Let me label that.

00:06:20.950 --> 00:06:22.860
I'm going to do a big diagram
of the heart in a second.

00:06:26.110 --> 00:06:27.610
And why are they
de-oxygenated?

00:06:27.610 --> 00:06:31.100
Because this is blood returning
from our legs if

00:06:31.100 --> 00:06:35.330
we're running, or returning from
our brain, that had to

00:06:35.330 --> 00:06:37.450
use respiration-- or maybe we're
working out and it's

00:06:37.450 --> 00:06:40.370
returning from our biceps, but
it's de-oxygenated blood.

00:06:40.370 --> 00:06:42.400
It shows up right here
in the right atrium.

00:06:42.400 --> 00:06:45.280
It's on our left, but this
guy's right-hand side.

00:06:45.280 --> 00:06:47.400
From the right atrium,
it gets pumped

00:06:47.400 --> 00:06:50.630
into the right ventricle.

00:06:50.630 --> 00:06:53.860
It actually passively flows
into the right ventricle.

00:06:53.860 --> 00:06:56.530
The ventricles do all the
pumping, then the ventricle

00:06:56.530 --> 00:07:00.260
contracts and pumps this blood
right here-- and you don't see

00:07:00.260 --> 00:07:02.980
it, but it's going behind
this part right here.

00:07:02.980 --> 00:07:05.740
It goes from here through
this pipe.

00:07:05.740 --> 00:07:06.580
So you don't see it.

00:07:06.580 --> 00:07:09.970
I'm going to do a detailed
diagram in a second-- into the

00:07:09.970 --> 00:07:11.400
pulmonary artery.

00:07:11.400 --> 00:07:12.930
We're going away
from the heart.

00:07:12.930 --> 00:07:14.790
This was a vein, right?

00:07:14.790 --> 00:07:19.640
This is a vein going
to the heart.

00:07:19.640 --> 00:07:24.130
This is a vein, inferior
vena cava vein.

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This is superior vena cava.

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These are veins.

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They're de-oxygenated.

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Then I'm pumping this
de-oxygenated blood away from

00:07:30.510 --> 00:07:32.340
the heart to the lungs.

00:07:32.340 --> 00:07:35.620
Now this de-oxygenated blood,
this is in an artery, right?

00:07:35.620 --> 00:07:37.670
This is in the pulmonary
artery.

00:07:37.670 --> 00:07:41.230
It gets oxygenated and now
it's a pulmonary vein.

00:07:41.230 --> 00:07:45.570
And once it's oxygenated, it
shows up here in the left--

00:07:45.570 --> 00:07:49.060
let me do a better color than
that-- it shows up right here

00:07:49.060 --> 00:07:50.590
in the left atrium.

00:07:50.590 --> 00:07:53.830
Atrium, you can imagine-- it's
kind of a room with a skylight

00:07:53.830 --> 00:07:57.650
or that's open to the outside
and in both of these cases,

00:07:57.650 --> 00:07:59.900
things are entering from above--
not sunlight, but

00:07:59.900 --> 00:08:02.320
blood is entering from above.

00:08:02.320 --> 00:08:05.320
On the right atrium, the blood
is entering from above.

00:08:05.320 --> 00:08:08.110
And in the left atrium, the
blood is entering-- and

00:08:08.110 --> 00:08:09.950
remember, the left atrium is
on the right-hand side from

00:08:09.950 --> 00:08:12.580
our point of view-- on the
left atrium, the blood is

00:08:12.580 --> 00:08:16.320
entering from above from
the lungs, from

00:08:16.320 --> 00:08:18.120
the pulmonary veins.

00:08:18.120 --> 00:08:20.110
Veins go to the heart.

00:08:20.110 --> 00:08:24.500
Then it goes into-- and I'll go
into more detail-- into the

00:08:24.500 --> 00:08:27.810
left ventricle and then the
left ventricle pumps that

00:08:27.810 --> 00:08:33.020
oxygenated blood to the rest
of the body via the

00:08:33.020 --> 00:08:34.610
non-pulmonary arteries.

00:08:34.610 --> 00:08:36.539
So everything pumps out.

00:08:36.539 --> 00:08:39.520
Let me make it a nice dark,
non-blue color.

00:08:39.520 --> 00:08:41.179
So it pumps it out
through there.

00:08:41.179 --> 00:08:43.169
You don't see it right here,
the way it's drawn.

00:08:43.169 --> 00:08:45.060
It's a little bit of
a strange drawing.

00:08:45.060 --> 00:08:47.610
It's hard to visualize, but I'll
show it in more detail

00:08:47.610 --> 00:08:49.420
and then it goes to the
rest of the body.

00:08:49.420 --> 00:08:51.130
Let me show you that
detail right now.

00:08:54.670 --> 00:08:56.750
So we said, we have
de-oxygenated blood.

00:08:56.750 --> 00:08:58.350
Let's label it right here.

00:08:58.350 --> 00:09:01.590
This is the superior
vena cava.

00:09:01.590 --> 00:09:03.960
This is a vein from the upper
part of our body from

00:09:03.960 --> 00:09:04.980
our arms and heads.

00:09:04.980 --> 00:09:06.540
This is the inferior
vena vaca.

00:09:06.540 --> 00:09:10.910
This is veins from our abdomen
and from our legs and the rest

00:09:10.910 --> 00:09:11.810
of our body.

00:09:11.810 --> 00:09:14.560
So it it first enters
the right atrium.

00:09:14.560 --> 00:09:18.460
Remember, we call the right
atrium because this is

00:09:18.460 --> 00:09:20.650
someone's heart facing us, even
though this is on the

00:09:20.650 --> 00:09:21.710
left-hand side.

00:09:21.710 --> 00:09:22.880
It enters through here.

00:09:22.880 --> 00:09:24.790
It's de-oxygenated blood.

00:09:24.790 --> 00:09:26.240
It's coming from veins.

00:09:26.240 --> 00:09:28.260
the body used the oxygen.

00:09:28.260 --> 00:09:31.100
Then it shows up in the right
ventricle, right?

00:09:31.100 --> 00:09:34.670
These are valves in our heart.

00:09:34.670 --> 00:09:37.440
And it passively, once the right
ventricle pumps and then

00:09:37.440 --> 00:09:40.350
releases, it has a vacuum and
it pulls more blood from the

00:09:40.350 --> 00:09:40.770
right atrium.

00:09:40.770 --> 00:09:44.550
It pumps again and then it
pushes it through here.

00:09:44.550 --> 00:09:47.110
Now this blood right here--
remember, this one still is

00:09:47.110 --> 00:09:49.140
de-oxygenated blood.

00:09:49.140 --> 00:09:52.910
De-oxygenated blood goes
to the lungs to become

00:09:52.910 --> 00:09:54.190
oxygenated.

00:09:54.190 --> 00:09:59.350
So this right here is the
pulmonary-- I'm using the word

00:09:59.350 --> 00:10:02.370
pulmonary because it's going
to or from the lungs.

00:10:02.370 --> 00:10:03.970
It's dealing with the lungs.

00:10:03.970 --> 00:10:05.850
And it's going away
from the heart.

00:10:05.850 --> 00:10:13.590
It's the pulmonary artery
and it is de-oxygenated.

00:10:17.750 --> 00:10:25.190
Then it goes to the heart, rubs
up against some alveoli

00:10:25.190 --> 00:10:31.060
and then gets oxygenated and
then it comes right back.

00:10:31.060 --> 00:10:36.990
Now this right here, we're
going to the heart.

00:10:36.990 --> 00:10:38.240
So that's a vein.

00:10:40.380 --> 00:10:45.650
It's in the loop with the lungs
so it's a pulmonary vein

00:10:45.650 --> 00:10:49.000
and it rubbed up against the
alveoli and got the oxygen

00:10:49.000 --> 00:10:50.625
diffused into it so
it is oxygenated.

00:10:53.930 --> 00:10:56.740
And then it flows into
your left atrium.

00:10:56.740 --> 00:10:58.520
Now, the left atrium, once
again, from our point of view,

00:10:58.520 --> 00:11:00.530
is on the right-hand side, but
from the dude looking at it,

00:11:00.530 --> 00:11:02.230
it's his left-hand side.

00:11:02.230 --> 00:11:04.050
So it goes into the
left atrium.

00:11:04.050 --> 00:11:06.650
Now in the left ventricle, after
it's done pumping, it

00:11:06.650 --> 00:11:10.110
expands and that oxygenated
blood flows

00:11:10.110 --> 00:11:11.380
into the left ventricle.

00:11:11.380 --> 00:11:13.880
Then the left ventricle-- the
ventricles are what do all the

00:11:13.880 --> 00:11:16.870
pumping-- it squeezes and
then it pumps the

00:11:16.870 --> 00:11:19.650
blood into the aorta.

00:11:22.180 --> 00:11:24.125
This is an artery.

00:11:27.270 --> 00:11:28.200
Why is it an artery?

00:11:28.200 --> 00:11:30.390
Because we're going away
from the heart.

00:11:30.390 --> 00:11:31.950
Is it a pulmonary artery?

00:11:31.950 --> 00:11:35.370
No, we're not dealing with
the lungs anymore.

00:11:35.370 --> 00:11:37.020
We dealt with the lungs when
we went from the right

00:11:37.020 --> 00:11:38.920
ventricle, went to the
lungs in a loop,

00:11:38.920 --> 00:11:41.560
back to the left atrium.

00:11:41.560 --> 00:11:43.770
Now we're in the
left ventricle.

00:11:43.770 --> 00:11:44.900
We pump into the aorta.

00:11:44.900 --> 00:11:46.550
Now this is to go to the
rest of the body.

00:11:46.550 --> 00:11:50.020
This is an artery, a
non-pulmonary artery-- and it

00:11:50.020 --> 00:11:51.270
is oxygenated.

00:11:53.940 --> 00:11:56.490
So when we're dealing with
non-pulmonary arteries, we're

00:11:56.490 --> 00:12:00.040
oxygenated, but a pulmonary
artery has no oxygen.

00:12:00.040 --> 00:12:02.500
It's going away from the heart
to get the oxygen.

00:12:02.500 --> 00:12:05.250
Pulmonary vein comes from the
lungs to the heart with

00:12:05.250 --> 00:12:08.950
oxygen, but the rest of the
veins go to the heart without

00:12:08.950 --> 00:12:11.740
oxygen because they want to
go into that loop on the

00:12:11.740 --> 00:12:13.880
pulmonary loop right there.

00:12:13.880 --> 00:12:14.700
So I'll leave you there.

00:12:14.700 --> 00:12:16.480
Hopefully that gives-- actually,
let's go back to

00:12:16.480 --> 00:12:17.200
that first diagram.

00:12:17.200 --> 00:12:20.780
I think you have a sense of how
the heart is dealing, but

00:12:20.780 --> 00:12:22.750
let's go look at the rest
of the body and just

00:12:22.750 --> 00:12:25.340
get a sense of things.

00:12:25.340 --> 00:12:27.170
You can look this up on
Wikipedia if you like.

00:12:27.170 --> 00:12:29.220
All of these different
branching points have

00:12:29.220 --> 00:12:34.200
different names to them, but
you can see right here you

00:12:34.200 --> 00:12:37.450
have kind of a branching off, a
little bit below the heart.

00:12:37.450 --> 00:12:39.080
This is actually the
celiac trunk.

00:12:42.370 --> 00:12:45.040
Celiac, if I remember correctly,
kind of refers to

00:12:45.040 --> 00:12:46.080
an abdomen.

00:12:46.080 --> 00:12:50.510
So this blood that-- your
hepatic artery.

00:12:50.510 --> 00:12:53.940
Hepatic deals with the liver.

00:12:53.940 --> 00:12:56.800
Your hepatic artery branches off
of this to get blood flow

00:12:56.800 --> 00:12:57.970
to the liver.

00:12:57.970 --> 00:13:01.120
It also gives blood flow to
your stomach so it's very

00:13:01.120 --> 00:13:02.780
important in digestion
and all that.

00:13:02.780 --> 00:13:05.240
And then let's say this
is the hepatic trunk.

00:13:05.240 --> 00:13:07.010
Your liver is sitting
like that.

00:13:07.010 --> 00:13:10.070
Hepatic trunk-- it delivers
oxygen to the liver.

00:13:10.070 --> 00:13:12.120
The liver is doing
respiration.

00:13:12.120 --> 00:13:15.910
It takes up the oxygen
and then it

00:13:15.910 --> 00:13:17.550
gives up carbon dioxide.

00:13:17.550 --> 00:13:21.790
So it becomes de-oxygenated and
then it flows back in and

00:13:21.790 --> 00:13:24.710
to the inferior vena cava,
into the vein.

00:13:24.710 --> 00:13:26.200
I want to make it clear--
it's a loop.

00:13:26.200 --> 00:13:27.480
It's a big loop.

00:13:27.480 --> 00:13:30.620
The blood doesn't just flow out
someplace and then come

00:13:30.620 --> 00:13:31.290
back someplace else.

00:13:31.290 --> 00:13:33.200
This is just one big loop.

00:13:33.200 --> 00:13:35.420
And if you want to know at any
given point in time, depending

00:13:35.420 --> 00:13:42.010
on your size, there's about
five liters of blood.

00:13:42.010 --> 00:13:46.240
And I looked it up-- it takes
the average red blood cell to

00:13:46.240 --> 00:13:49.390
go from one point in the
circulatory system and go

00:13:49.390 --> 00:13:52.630
through the whole system and
come back, 20 seconds.

00:13:52.630 --> 00:13:54.330
That's an average because you
can imagine there might be

00:13:54.330 --> 00:13:56.480
some red blood cells that get
stuck someplace and take a

00:13:56.480 --> 00:13:58.930
little bit more time and some
go through the completely

00:13:58.930 --> 00:13:59.900
perfect route.

00:13:59.900 --> 00:14:01.790
Actually, the 20 seconds
might be closer

00:14:01.790 --> 00:14:02.740
to the perfect route.

00:14:02.740 --> 00:14:04.190
I've never timed it myself.

00:14:04.190 --> 00:14:06.230
But it's an interesting thing to
look at and to think about

00:14:06.230 --> 00:14:07.690
what's connected to what.

00:14:07.690 --> 00:14:12.150
You have these these arteries up
here that they first branch

00:14:12.150 --> 00:14:17.170
off the arteries up here from
the aorta into the head and

00:14:17.170 --> 00:14:20.650
the neck and the arm arteries
and then later they go down

00:14:20.650 --> 00:14:26.560
and they flow blood to
the rest of the body.

00:14:26.560 --> 00:14:28.950
So anyway, this is a pretty
interesting idea.

00:14:28.950 --> 00:14:35.250
In the next video, what I want
to do is talk about, how does

00:14:35.250 --> 00:14:40.110
the hemoglobin know when
to dump the oxygen?

00:14:40.110 --> 00:14:43.310
Or even better, where to dump
the oxygen-- because maybe I'm

00:14:43.310 --> 00:14:45.830
running so I need a lot of
oxygen in the capillaries

00:14:45.830 --> 00:14:47.340
around my thigh muscles.

00:14:47.340 --> 00:14:49.410
I don't need them necessarily
in my hands.

00:14:49.410 --> 00:14:53.700
How does the body optimize where
the oxygen is actually

00:14:53.700 --> 00:14:53.915
delivering?

00:14:53.915 --> 00:14:55.670
It's actually fascinating.


Red blood cells

WEBVTT
Kind: captions
Language: en

00:00:00.540 --> 00:00:03.870
In the last video on the lungs
or the gas exchange in our

00:00:03.870 --> 00:00:07.540
bodies or on the pulmonary
system, we left off with the

00:00:07.540 --> 00:00:09.290
alveolar sacs.

00:00:09.290 --> 00:00:10.690
Let me draw one right here.

00:00:10.690 --> 00:00:14.400
So we have these alveolar sacs
that I talked about and

00:00:14.400 --> 00:00:18.090
they're in these little
clumps like this.

00:00:18.090 --> 00:00:20.460
Let me draw a couple of them
just so you get the idea.

00:00:20.460 --> 00:00:23.630
And if you remember from the
last video, these are kind of

00:00:23.630 --> 00:00:27.380
where air goes in through our
trachea, then that splits up

00:00:27.380 --> 00:00:29.680
into our bronchi, and then
those split into the

00:00:29.680 --> 00:00:31.730
bronchioles, and
the bronchioles

00:00:31.730 --> 00:00:34.810
terminate at these alveoli.

00:00:34.810 --> 00:00:36.790
So that's the alveoli.

00:00:36.790 --> 00:00:39.950
These are these super-small sacs
that we talked about in

00:00:39.950 --> 00:00:41.680
the last video on the
pulmonary system.

00:00:41.680 --> 00:00:43.420
You might want to watch
that video if none

00:00:43.420 --> 00:00:44.420
of this sounds familiar.

00:00:44.420 --> 00:00:47.180
And then of course we have our
bronchiole that feeds into

00:00:47.180 --> 00:00:49.920
this, and then that might have
branched off from another one

00:00:49.920 --> 00:00:52.160
that feeds into another set of
alveolar sacs, but I don't

00:00:52.160 --> 00:00:53.270
want to get too focused
on that.

00:00:53.270 --> 00:00:54.520
I covered that in
the last video.

00:01:05.630 --> 00:01:10.460
In the last video, we saw that
air, when we breathe in, when

00:01:10.460 --> 00:01:13.970
our diaphragm contracts and
makes our lungs expand and

00:01:13.970 --> 00:01:17.380
fill up that space,
air comes in.

00:01:17.380 --> 00:01:23.020
Air comes in and that air that
comes in is going to be-- as

00:01:23.020 --> 00:01:27.780
we're breathing atmospheric
air-- it's going to be 21%

00:01:27.780 --> 00:01:38.450
oxygen and it's going
to be 78% nitrogen.

00:01:38.450 --> 00:01:41.120
And actually, in our atmosphere,
carbon dioxide is

00:01:41.120 --> 00:01:43.290
actually almost a trace gas.

00:01:43.290 --> 00:01:44.540
It's less than 1%.

00:01:50.680 --> 00:01:53.370
So any time you breathe in on
Earth, this is what you're

00:01:53.370 --> 00:01:54.770
going to get.

00:01:54.770 --> 00:01:57.880
And we said in the last video
that you have these

00:01:57.880 --> 00:02:01.320
capillaries, these pulmonary
capillaries that are running

00:02:01.320 --> 00:02:03.420
all along the side
of these alveoli.

00:02:03.420 --> 00:02:09.160
So let me draw those pulmonary
capillaries-- and so when they

00:02:09.160 --> 00:02:12.390
are de-oxygenated-- so they come
here to be oxygenated.

00:02:12.390 --> 00:02:13.700
So when they're de-oxygenated,
they might

00:02:13.700 --> 00:02:14.950
look a little purplish.

00:02:21.880 --> 00:02:25.050
And then they pick up the
oxygen from inside the

00:02:25.050 --> 00:02:28.770
alveoli-- or the oxygen diffuses
across the membrane

00:02:28.770 --> 00:02:32.890
of the alveoli, into these
capillaries, into these super

00:02:32.890 --> 00:02:34.010
small tubes.

00:02:34.010 --> 00:02:36.850
And then once they do, that
makes the blood red.

00:02:36.850 --> 00:02:40.470
I'm going to talk in a little
bit about why it becomes red.

00:02:40.470 --> 00:02:43.720
So then it becomes red, and now
that the blood is red, it

00:02:43.720 --> 00:02:44.950
has its oxygen.

00:02:44.950 --> 00:02:46.600
The whole point is to
get the oxygen.

00:02:46.600 --> 00:02:51.420
It's ready to go back
to the heart.

00:02:51.420 --> 00:02:53.260
So that's just one little
part of it.

00:02:53.260 --> 00:02:56.140
And we learned in the last video
that something that goes

00:02:56.140 --> 00:03:00.230
away from the heart-- so this is
going away from the heart--

00:03:00.230 --> 00:03:05.450
that is an artery. "A
for Away" - Artery.

00:03:05.450 --> 00:03:09.890
And something that's going
towards the heart is a vein.

00:03:09.890 --> 00:03:14.920
So this right here is a vein.

00:03:14.920 --> 00:03:17.910
Now one question-- and
this actually came

00:03:17.910 --> 00:03:19.920
up in the last video.

00:03:19.920 --> 00:03:23.530
Someone asked-- which I think is
a very good question-- is,

00:03:23.530 --> 00:03:27.360
gee, when we breathe in, most
of the air is nitrogen.

00:03:27.360 --> 00:03:28.990
Only 21% is oxygen.

00:03:28.990 --> 00:03:30.610
What happens to all that
nitrogen there?

00:03:30.610 --> 00:03:33.150
How come that doesn't
go into our blood?

00:03:33.150 --> 00:03:35.160
And that's actually an
excellent question.

00:03:35.160 --> 00:03:37.960
So to answer that, I think that
actually helps explain

00:03:37.960 --> 00:03:39.430
what's going on here.

00:03:39.430 --> 00:03:40.680
Let's draw a little
bit bigger.

00:03:48.040 --> 00:03:51.320
This is the inside of
of an alveolus.

00:03:51.320 --> 00:03:55.560
This is its membrane right here,
super thin, almost one

00:03:55.560 --> 00:03:56.960
cell thick.

00:03:56.960 --> 00:04:01.800
And then you have a capillary
running right next to it.

00:04:01.800 --> 00:04:03.180
Let me do that in
a neutral color.

00:04:03.180 --> 00:04:05.380
So you have a capillary
that's maybe running

00:04:05.380 --> 00:04:06.630
right along the surface.

00:04:14.130 --> 00:04:18.430
And this is porous to gases
like oxygen, and nitrogen,

00:04:18.430 --> 00:04:19.550
carbon dioxide.

00:04:19.550 --> 00:04:22.040
And what we have here-- let's
say that this is-- so the

00:04:22.040 --> 00:04:23.340
heart is over here.

00:04:25.880 --> 00:04:29.020
So this is blood coming from
the heart and then this is

00:04:29.020 --> 00:04:30.430
going to go back to the heart.

00:04:30.430 --> 00:04:31.530
Well, the heart's
on both sides.

00:04:31.530 --> 00:04:32.890
So let me write it this way.

00:04:32.890 --> 00:04:40.530
From the heart and
to the heart.

00:04:40.530 --> 00:04:43.550
And what you have here is--
when we're coming from the

00:04:43.550 --> 00:04:45.970
heart, this is de-oxygenated
blood and it's actually going

00:04:45.970 --> 00:04:48.396
to have a high concentration
of carbon dioxide.

00:04:53.950 --> 00:04:55.500
I already did nitrogen
as green.

00:04:55.500 --> 00:04:58.800
Let me do carbon dioxide
as orange.

00:04:58.800 --> 00:05:00.740
There's a lot of carbon dioxide
and actually carbon

00:05:00.740 --> 00:05:04.000
dioxide actually gets diffused
in the blood.

00:05:04.000 --> 00:05:06.280
It actually is carried in
the plasma of the blood.

00:05:06.280 --> 00:05:08.590
It's not carried by red blood
cells that we're going to talk

00:05:08.590 --> 00:05:09.810
about in a second.

00:05:09.810 --> 00:05:12.270
So that's a bunch of carbon
dioxide here.

00:05:12.270 --> 00:05:15.880
And the concentration of
carbon dioxide in the

00:05:15.880 --> 00:05:17.580
de-oxygenated blood is going
to be higher than the

00:05:17.580 --> 00:05:22.450
concentration of carbon dioxide
in the alveolus.

00:05:22.450 --> 00:05:25.800
so if this is porous to carbon
dioxide, this membrane-- and

00:05:25.800 --> 00:05:32.150
it is, these carbon dioxide
molecules are going to diffuse

00:05:32.150 --> 00:05:35.120
into the alveolus.

00:05:35.120 --> 00:05:40.340
Now on the other side of that--
we have oxygen here.

00:05:40.340 --> 00:05:41.270
We're breathing it in.

00:05:41.270 --> 00:05:44.550
The air is 21% oxygen so you're
actually going to have

00:05:44.550 --> 00:05:47.210
a lot more oxygen than
carbon dioxide.

00:05:47.210 --> 00:05:48.830
And this is de-oxygenated
blood.

00:05:48.830 --> 00:05:51.690
We used all of the oxygen in our
body and we'll talk more

00:05:51.690 --> 00:05:54.800
about that either at the end of
this video or in a future

00:05:54.800 --> 00:05:58.710
video on how we use it or where
it goes in our body, but

00:05:58.710 --> 00:06:02.020
there's no oxygen here so the
oxygen is going to be taken--

00:06:02.020 --> 00:06:08.450
it's going to diffuse across
this membrane because the

00:06:08.450 --> 00:06:10.620
concentration of
oxygen is low.

00:06:10.620 --> 00:06:13.890
Now the question is-- so
immediately you see that as

00:06:13.890 --> 00:06:15.946
the oxygen diffuses across
this membrane, all of a

00:06:15.946 --> 00:06:17.460
sudden, this is oxygenated
blood ready to

00:06:17.460 --> 00:06:19.270
go back to the heart.

00:06:19.270 --> 00:06:21.950
So this transition between
artery and vein is a very

00:06:21.950 --> 00:06:23.040
subtle thing.

00:06:23.040 --> 00:06:24.990
Very clearly here, you
say that, OK, this is

00:06:24.990 --> 00:06:26.440
going from the heart.

00:06:26.440 --> 00:06:30.360
This is our vein.

00:06:30.360 --> 00:06:33.450
This is going to the
heart-- sorry.

00:06:33.450 --> 00:06:34.440
I always get confused.

00:06:34.440 --> 00:06:36.930
This is going away from the
heart-- and I was looking for

00:06:36.930 --> 00:06:38.040
an A and I wrote from.

00:06:38.040 --> 00:06:41.610
This is away from the heart
so this is an artery.

00:06:41.610 --> 00:06:44.330
And this is going to the heart
so this is a vein.

00:06:44.330 --> 00:06:45.770
So you could make
the division.

00:06:45.770 --> 00:06:47.780
You could say, OK, once it's
oxygenated, maybe we're going

00:06:47.780 --> 00:06:50.220
back to the heart, but it's kind
of an arbitrary-- sorry.

00:06:50.220 --> 00:06:53.060
I spelled artery wrong.

00:06:53.060 --> 00:06:55.660
These are my flaws.

00:06:55.660 --> 00:06:57.210
Spelling was never
my strong suit.

00:06:57.210 --> 00:06:59.840
So it's hard to say where
the artery ends

00:06:59.840 --> 00:07:00.830
and the vein begins.

00:07:00.830 --> 00:07:04.320
A good demarcation is when the
carbon dioxide concentration

00:07:04.320 --> 00:07:07.840
goes low and that the oxygen
concentration goes high.

00:07:07.840 --> 00:07:09.690
That's a good time, where
we start from

00:07:09.690 --> 00:07:13.060
the pulmonary artery.

00:07:13.060 --> 00:07:16.180
Probably in the next video, I
will a make a very-- you'll

00:07:16.180 --> 00:07:18.790
see why the pulmonary arteries
are special, because pulmonary

00:07:18.790 --> 00:07:22.230
arteries coming away from the
heart have no oxygen or very

00:07:22.230 --> 00:07:26.590
little oxygen and they have
a lot of carbon dioxide.

00:07:26.590 --> 00:07:34.750
So pulmonary veins, which is--
it's arbitrary where the

00:07:34.750 --> 00:07:36.160
artery turns into a vein.

00:07:36.160 --> 00:07:38.520
Once it gets oxygenated, it's
ready to go back to the heart.

00:07:38.520 --> 00:07:42.070
It's a pulmonary vein and
it is oxygenated.

00:07:42.070 --> 00:07:47.326
So it has oxygenated-- and we
could write de-oxygenated.

00:07:52.280 --> 00:07:54.900
Now the reason why I say it's
special besides the fact that

00:07:54.900 --> 00:07:59.110
pulmonary arteries and veins go
to and from the lungs, is

00:07:59.110 --> 00:08:00.400
that they're kind
of the opposite.

00:08:00.400 --> 00:08:02.680
Because in the rest of the body
when we're going away

00:08:02.680 --> 00:08:05.420
from the heart or we're talking
about arteries, you're

00:08:05.420 --> 00:08:07.910
going to see that that's
oxygenated blood, while when

00:08:07.910 --> 00:08:10.020
we're going away from the heart
to the lungs, that's

00:08:10.020 --> 00:08:11.480
de-oxygenated blood.

00:08:11.480 --> 00:08:14.260
Similarly in the rest of the
body, when we're going to the

00:08:14.260 --> 00:08:16.560
heart, where you're to see
that that's de-oxygenated

00:08:16.560 --> 00:08:19.220
blood, but in the pulmonary
vein, when we're going to the

00:08:19.220 --> 00:08:23.340
heart, it's oxygenated because
the lungs are what take up the

00:08:23.340 --> 00:08:26.630
carbon dioxide and give
us the oxygen.

00:08:26.630 --> 00:08:30.320
Now I still haven't answered
that interesting question that

00:08:30.320 --> 00:08:34.370
rose on the message board
on the last video.

00:08:34.370 --> 00:08:37.330
What happens to the 78% of
nitrogen that's sitting here?

00:08:37.330 --> 00:08:43.320
There's just a ton of nitrogen
over here, more than the

00:08:43.320 --> 00:08:45.350
oxygen, a lot more than
the carbon dioxide.

00:08:45.350 --> 00:08:48.050
What happens to all of these
nitrogen molecules?

00:08:48.050 --> 00:08:51.550
And the answer is, nitrogen can
diffuse and does diffuse

00:08:51.550 --> 00:08:56.400
into the blood, but the blood's
ability to take in

00:08:56.400 --> 00:08:58.280
nitrogen isn't that high.

00:08:58.280 --> 00:09:00.930
And you might say, well,
why is oxygen special?

00:09:00.930 --> 00:09:03.800
Why can the blood take
up oxygen so

00:09:03.800 --> 00:09:05.360
much easier than nitrogen?

00:09:05.360 --> 00:09:09.250
And that's where the red blood
cells come into play.

00:09:09.250 --> 00:09:09.920
Let me write this down.

00:09:09.920 --> 00:09:11.520
I'll write it in red.

00:09:11.520 --> 00:09:16.520
Red blood cells, which
are fascinating on a

00:09:16.520 --> 00:09:20.050
whole set of levels.

00:09:20.050 --> 00:09:23.470
What red blood cells-- these
are these cells that are

00:09:23.470 --> 00:09:28.010
sitting in-- they're flowing
through our circulatory system

00:09:28.010 --> 00:09:30.260
and they look kind of
like lozenges, if I

00:09:30.260 --> 00:09:31.830
were to draw one.

00:09:31.830 --> 00:09:34.400
They're kind of like a flattened
sphere with a little

00:09:34.400 --> 00:09:38.090
divot on either side of it--
a lot like a lozenge.

00:09:38.090 --> 00:09:39.730
So if I were to draw it from
the side, it might look

00:09:39.730 --> 00:09:41.480
something like-- well, from the
side, it would look like

00:09:41.480 --> 00:09:43.530
that and if you could see
through it, there'd be a

00:09:43.530 --> 00:09:45.140
little divot on each side.

00:09:45.140 --> 00:09:47.190
If I were to draw it at an
angle, it would look

00:09:47.190 --> 00:09:48.440
something like this.

00:09:51.660 --> 00:09:54.200
There'd be a little divot on
that side and there'd be a

00:09:54.200 --> 00:09:55.960
similar divot on
the other side.

00:09:55.960 --> 00:09:58.750
And red blood cells-- and I
could do a whole set of videos

00:09:58.750 --> 00:10:03.650
just on red blood cells--
they contain hemoglobin.

00:10:03.650 --> 00:10:05.250
Maybe we'll do a whole
video on hemoglobin.

00:10:05.250 --> 00:10:11.420
The hemoglobin are these
small proteins that

00:10:11.420 --> 00:10:13.330
contain four hem groups.

00:10:13.330 --> 00:10:19.050
So inside of red blood cells,
you have millions of

00:10:19.050 --> 00:10:20.750
hemoglobin proteins.

00:10:20.750 --> 00:10:23.460
And the hemoglobin proteins--
I'll just draw them as this--

00:10:23.460 --> 00:10:25.070
they have these four
heme groups.

00:10:25.070 --> 00:10:27.380
And heme groups, the main
component is iron.

00:10:27.380 --> 00:10:29.600
And that's why iron
is so important.

00:10:29.600 --> 00:10:31.990
If you don't have enough iron,
you're going to have trouble

00:10:31.990 --> 00:10:35.450
processing oxygen in your blood
and your hemoglobin

00:10:35.450 --> 00:10:36.340
won't be functional enough.

00:10:36.340 --> 00:10:37.350
But it has iron on it.

00:10:37.350 --> 00:10:39.350
It has four of these
heme groups.

00:10:39.350 --> 00:10:43.750
And each of these heme groups
can bond to oxygen molecules.

00:10:43.750 --> 00:10:46.140
They're very good binders
of oxygen.

00:10:46.140 --> 00:10:48.370
And we're going to see in a
little bit-- probably the next

00:10:48.370 --> 00:10:51.430
video-- how they release the
oxygen, but this has tons,

00:10:51.430 --> 00:10:56.010
this has millions of heme groups
in it and the oxygen

00:10:56.010 --> 00:11:00.120
diffuses across the membrane
of the red blood cells and

00:11:00.120 --> 00:11:04.970
bonds to to the heme groups
on your hemoglobin.

00:11:04.970 --> 00:11:09.470
So because the red blood cells
have the hemoglobin inside of

00:11:09.470 --> 00:11:12.380
them, they're like these sponges
for oxygen because

00:11:12.380 --> 00:11:14.340
hemoglobin is so good
at taking in oxygen.

00:11:14.340 --> 00:11:17.170
So the red blood cells are able
to essentially suck up

00:11:17.170 --> 00:11:19.710
all of the oxygen out
of the plasma.

00:11:19.710 --> 00:11:22.300
The plasma we can view as just
the general fluid of the

00:11:22.300 --> 00:11:24.500
blood, not including the
red blood cells.

00:11:24.500 --> 00:11:29.320
So the red blood cell
here isn't so red.

00:11:29.320 --> 00:11:32.380
And the reason-- and this is the
key point-- the reason why

00:11:32.380 --> 00:11:35.610
it's not so red-- maybe we had
a red blood cell over here--

00:11:35.610 --> 00:11:36.190
let me make it clear.

00:11:36.190 --> 00:11:38.450
Carbon dioxide for
the most part is

00:11:38.450 --> 00:11:41.390
traveling within the plasma.

00:11:41.390 --> 00:11:44.640
It gets absorbed into the actual
fluid and I'll talk

00:11:44.640 --> 00:11:45.500
about it in a future video.

00:11:45.500 --> 00:11:47.590
It's actually in a slightly
different form.

00:11:47.590 --> 00:11:50.820
It's as carbonic acid and that's
actually a key point

00:11:50.820 --> 00:11:54.040
for how the plasma knows where
to dump the oxygen, but I'll

00:11:54.040 --> 00:11:55.720
talk about that in
a future video.

00:11:55.720 --> 00:11:59.540
But over here, this red blood
cell has a bunch of hemoglobin

00:11:59.540 --> 00:12:02.840
proteins in it, but those
hemoglobin proteins have

00:12:02.840 --> 00:12:04.190
dumped their oxygen.

00:12:04.190 --> 00:12:07.250
And it actually turns out it's
the hemoglobin-- so with

00:12:07.250 --> 00:12:09.080
oxygen, hemoglobin looks red.

00:12:11.980 --> 00:12:13.660
It reflects red light.

00:12:13.660 --> 00:12:19.350
When it doesn't have oxygen,
hemoglobin does not look red.

00:12:19.350 --> 00:12:23.190
It looks kind of purplish,
bluish, darkish-- something.

00:12:23.190 --> 00:12:26.880
And that's why in most of your
body, your veins that have

00:12:26.880 --> 00:12:31.770
de-oxygenated red blood cells
look kind of bluish.

00:12:31.770 --> 00:12:34.380
And the reason why it changes
color is that when the oxygen

00:12:34.380 --> 00:12:37.860
bonds to the hem sites on the
hemoglobin, it actually

00:12:37.860 --> 00:12:40.480
changes the entire confirmation,
the entire

00:12:40.480 --> 00:12:41.660
structure of the protein.

00:12:41.660 --> 00:12:43.160
We've see that multiple times.

00:12:43.160 --> 00:12:45.950
The whole protein folds in
such a way that all of a

00:12:45.950 --> 00:12:49.340
sudden, instead of purplish or
dark light being reflected,

00:12:49.340 --> 00:12:50.690
now red light is reflected.

00:12:50.690 --> 00:12:54.130
And that's why red blood cells
will become red once they take

00:12:54.130 --> 00:12:54.920
the oxygen.

00:12:54.920 --> 00:12:56.240
But I'm going on a tangent.

00:12:56.240 --> 00:12:58.720
The whole point here is saying,
why we taking up so

00:12:58.720 --> 00:13:01.310
much more oxygen than nitrogen,
given that there's

00:13:01.310 --> 00:13:04.260
less oxygen in the atmosphere
than nitrogen?

00:13:04.260 --> 00:13:06.720
And the key is these
red blood cells.

00:13:06.720 --> 00:13:09.250
These red blood cells have these
millions of hemoglobin

00:13:09.250 --> 00:13:12.280
proteins inside of them and they
take them up and they sop

00:13:12.280 --> 00:13:14.280
up all of the oxygen
out of the plasma.

00:13:14.280 --> 00:13:23.870
Actually, they sop about
98.5% of the oxygen.

00:13:23.870 --> 00:13:25.560
So these red blood cells are
just traveling and they're

00:13:25.560 --> 00:13:27.440
going to go back to the heart.

00:13:27.440 --> 00:13:29.670
They are what make
our blood red.

00:13:29.670 --> 00:13:32.010
So you have this thing,
hemoglobin, that's sitting in

00:13:32.010 --> 00:13:32.770
red blood cells.

00:13:32.770 --> 00:13:34.380
It's sopping up all
the oxygen.

00:13:34.380 --> 00:13:37.290
So it keeps the oxygen
concentration and the actual

00:13:37.290 --> 00:13:38.610
plasma low.

00:13:38.610 --> 00:13:40.760
You have nothing like
that for nitrogen.

00:13:40.760 --> 00:13:43.350
There is no cell that's sopping
up the nitrogen.

00:13:43.350 --> 00:13:46.280
Nitrogen does not bond
to hemoglobin.

00:13:46.280 --> 00:13:49.030
So that's why oxygen
is taken up so

00:13:49.030 --> 00:13:50.990
much better than nitrogen.

00:13:50.990 --> 00:13:55.690
It's a very interesting question
because if you just

00:13:55.690 --> 00:13:57.700
think about how much nitrogen
is, it's kind of a very

00:13:57.700 --> 00:13:59.630
natural idea.

00:13:59.630 --> 00:14:02.640
Now I want to focus a little
bit on the red blood cell

00:14:02.640 --> 00:14:05.840
itself because it's
fascinating.

00:14:05.840 --> 00:14:08.240
In the video on the structure
of the cell, I start off

00:14:08.240 --> 00:14:10.020
saying, all cells have
a membrane and

00:14:10.020 --> 00:14:12.190
they all have DNA.

00:14:12.190 --> 00:14:22.565
Now, the fascinating thing about
a red blood cell-- I

00:14:22.565 --> 00:14:26.980
already said it has millions
of hemoglobin molecules or

00:14:26.980 --> 00:14:28.580
proteins inside of it.

00:14:28.580 --> 00:14:29.950
The fascinating thing
about a red blood

00:14:29.950 --> 00:14:32.120
cell-- it has no nucleus.

00:14:34.760 --> 00:14:38.200
And no DNA.

00:14:38.200 --> 00:14:40.550
This is mind boggling when
I first found out.

00:14:40.550 --> 00:14:41.980
I was like, well, why
is it a cell?

00:14:41.980 --> 00:14:43.860
Is it really even
a living thing?

00:14:43.860 --> 00:14:45.990
And it turns out when
it's growing,

00:14:45.990 --> 00:14:47.810
it does have a nucleus.

00:14:47.810 --> 00:14:52.310
All cells need a nucleus with
DNA in order to generate the

00:14:52.310 --> 00:14:56.530
proteins that build it up,
in order to exist and

00:14:56.530 --> 00:14:59.690
structurally make itself the way
it needs to be made, but

00:14:59.690 --> 00:15:02.820
the whole point of a red blood
cell is to contain as much

00:15:02.820 --> 00:15:05.030
hemoglobin as possible.

00:15:05.030 --> 00:15:07.490
And so you can imagine, this
is actually a favorable

00:15:07.490 --> 00:15:11.200
evolutionary trait, that as red
blood cells are ready to

00:15:11.200 --> 00:15:14.770
go into business, you've built
the whole structure, they

00:15:14.770 --> 00:15:16.230
actually get rid of
their nucleus.

00:15:16.230 --> 00:15:19.440
They actually push their nucleus
out of the cell and

00:15:19.440 --> 00:15:21.950
the whole reason why that's
beneficial is, that's more

00:15:21.950 --> 00:15:24.540
space for hemoglobin.

00:15:33.280 --> 00:15:36.730
Because the more hemoglobin you
have, the more oxygen you

00:15:36.730 --> 00:15:37.610
can take up.

00:15:37.610 --> 00:15:42.120
And I can do a ton of videos
on hemoglobin and all of

00:15:42.120 --> 00:15:44.040
that-- and actually, I'm going
to do a lot more on the

00:15:44.040 --> 00:15:46.370
circulatory system so don't
worry about that, but I want

00:15:46.370 --> 00:15:49.870
to go over one other really
interesting thing about

00:15:49.870 --> 00:15:50.560
hemoglobin.

00:15:50.560 --> 00:15:51.880
We already talked about
red blood cells.

00:15:51.880 --> 00:15:54.070
I think it's fascinating that
they actually don't have a

00:15:54.070 --> 00:15:55.370
nucleus in their mature form.

00:15:55.370 --> 00:15:56.730
They actually have
very short lives.

00:15:56.730 --> 00:16:00.360
They live maybe 80, 120 days
so they're not these long

00:16:00.360 --> 00:16:03.720
lived cells-- so it's almost
a philosophical question.

00:16:03.720 --> 00:16:07.250
Are are they still alive once
they've lost their DNA or are

00:16:07.250 --> 00:16:11.420
they just vessels for oxygen
that aren't really alive

00:16:11.420 --> 00:16:14.210
because they aren't regenerating
and producing

00:16:14.210 --> 00:16:15.530
their own DNA?

00:16:15.530 --> 00:16:17.980
So actually, instead of going
into the hemoglobin discussion

00:16:17.980 --> 00:16:19.390
right now, I'll leave you
there in this video.

00:16:19.390 --> 00:16:21.760
I realize I've been making
20-minute videos where my goal

00:16:21.760 --> 00:16:22.810
is really to make
ten-minute ones.

00:16:22.810 --> 00:16:25.055
So I'll leave you here and in
the next video, we'll talk

00:16:25.055 --> 00:16:28.590
more about hemoglobin and
the circulatory system.


The lungs and pulmonary system

WEBVTT
Kind: captions
Language: en

00:00:00.490 --> 00:00:03.280
I've done a bunch of videos
already on respiration.

00:00:03.280 --> 00:00:06.440
I think even before those
videos, you had a sense that

00:00:06.440 --> 00:00:13.510
we need oxygen and that
we release CO2.

00:00:13.510 --> 00:00:17.190
And if you watched the videos on
respiration, you know that

00:00:17.190 --> 00:00:21.490
we need the oxygen in order to
metabolize our food, in order

00:00:21.490 --> 00:00:25.980
to turn our food into ATPs
that can then drive other

00:00:25.980 --> 00:00:28.300
types of cellular functions--
or anything that we have to

00:00:28.300 --> 00:00:31.030
do; move, or breathe, or think,
or everything that we

00:00:31.030 --> 00:00:31.480
have to do.

00:00:31.480 --> 00:00:35.830
And that through the process of
respiration, we break down

00:00:35.830 --> 00:00:39.210
those sugars and we release
carbon dioxide.

00:00:39.210 --> 00:00:42.980
So in this video, what I want to
do is take a big step back

00:00:42.980 --> 00:00:45.770
and think about how we actually
get our oxygen into

00:00:45.770 --> 00:00:49.480
our body and how we release it
back out into the atmosphere.

00:00:49.480 --> 00:00:51.620
Another way to think about it is
how we ventilate ourselves.

00:00:54.250 --> 00:00:57.020
How do we get the oxygen in, and
how do we get the carbon

00:00:57.020 --> 00:00:58.200
dioxide out?

00:00:58.200 --> 00:01:01.560
And I think any of us could at
least start off this video.

00:01:01.560 --> 00:01:04.030
It starts off in either
our nose or our mouth.

00:01:04.030 --> 00:01:07.830
I always have a clogged sinus
so I often have to

00:01:07.830 --> 00:01:08.720
deal with my mouth.

00:01:08.720 --> 00:01:10.110
I sleep with my mouth often.

00:01:10.110 --> 00:01:12.350
But it always starts in our
nose or our mouths.

00:01:12.350 --> 00:01:15.850
Let me draw someone with
a nose and a mouth.

00:01:15.850 --> 00:01:17.850
So let's say that this
is my person.

00:01:17.850 --> 00:01:21.865
Maybe his mouth will be open
so that he can breathe.

00:01:25.350 --> 00:01:28.380
His eyes aren't important,
but just so

00:01:28.380 --> 00:01:29.800
you know it's a person.

00:01:29.800 --> 00:01:32.610
So this is my test subject
or the person I'm

00:01:32.610 --> 00:01:34.900
going to use to diagram.

00:01:34.900 --> 00:01:36.340
That's his ear.

00:01:36.340 --> 00:01:41.485
Maybe he has a bit of a-- let's
give him some hair.

00:01:45.210 --> 00:01:47.790
All of that is irrelevant,
but this is our guy.

00:01:47.790 --> 00:01:51.200
This is the guy that's going to
show us how we take air in

00:01:51.200 --> 00:01:54.120
and how we take air
out of the body.

00:01:54.120 --> 00:01:57.910
So let's go inside
of this guy.

00:01:57.910 --> 00:02:01.680
I can draw his outside
first. Let me see how

00:02:01.680 --> 00:02:02.510
well I can do this.

00:02:02.510 --> 00:02:04.390
So this is outside the guy.

00:02:04.390 --> 00:02:06.440
That doesn't look right.

00:02:06.440 --> 00:02:09.419
Let's say the guy looks
something like this and he's

00:02:09.419 --> 00:02:12.900
got-- this is his shoulders.

00:02:12.900 --> 00:02:14.010
That's our guy.

00:02:14.010 --> 00:02:14.900
All right.

00:02:14.900 --> 00:02:19.200
So in our mouth, we have our
oral cavity right there, which

00:02:19.200 --> 00:02:21.650
is just the space that
our mouth creates.

00:02:21.650 --> 00:02:22.770
We have our oral cavity.

00:02:22.770 --> 00:02:25.960
I could draw our tongue and all
of that and maybe I will.

00:02:25.960 --> 00:02:28.055
Maybe I'll draw the tongue.

00:02:32.020 --> 00:02:34.780
But you have this space inside
of the mouth-- call that the

00:02:34.780 --> 00:02:36.030
oral cavity.

00:02:46.900 --> 00:02:50.340
Oral for mouth, cavity for
space, or hole, or opening.

00:02:50.340 --> 00:02:52.700
And then also you have your
nostrils and they open up into

00:02:52.700 --> 00:02:53.950
a nasal cavity.

00:02:56.560 --> 00:02:59.310
So that's another big space
just like this.

00:02:59.310 --> 00:03:03.800
And we know that they connect at
the back of our nose or the

00:03:03.800 --> 00:03:05.020
back of our mouth.

00:03:05.020 --> 00:03:10.880
And this passage right here
where they connect is called

00:03:10.880 --> 00:03:12.130
the pharynx.

00:03:17.180 --> 00:03:19.640
When your air goes through your
nose-- they say breathing

00:03:19.640 --> 00:03:21.680
through your nose is better,
probably because it gets

00:03:21.680 --> 00:03:24.820
filtered by your nose hairs and
it gets warmed up and and

00:03:24.820 --> 00:03:27.180
what not, but you can breathe
through either side.

00:03:27.180 --> 00:03:32.900
The air goes in through either
your nasal cavity or your oral

00:03:32.900 --> 00:03:38.420
cavity and then comes back
through your pharynx and then

00:03:38.420 --> 00:03:41.220
the pharynx splits
into two pipes.

00:03:41.220 --> 00:03:44.140
One for-- well, one, air can
go down either one, but the

00:03:44.140 --> 00:03:45.660
other one is for food.

00:03:45.660 --> 00:03:47.700
So your pharynx gets split.

00:03:47.700 --> 00:03:51.720
In the back you have your
esophagus-- and we'll talk

00:03:51.720 --> 00:03:54.290
more about the esophagus
in a future video.

00:03:54.290 --> 00:03:57.540
In the back you have your
esophagus and in the front--

00:03:57.540 --> 00:04:00.030
let me draw a little dividing
line there.

00:04:00.030 --> 00:04:03.370
In the front, maybe this-- let
me make it connect like that.

00:04:03.370 --> 00:04:04.320
I was using yellow.

00:04:04.320 --> 00:04:05.870
I'm going to use yellow to
continue and I'm going to use

00:04:05.870 --> 00:04:07.730
green for the air.

00:04:07.730 --> 00:04:09.526
So it divides just like that.

00:04:12.350 --> 00:04:16.550
So behind your air pipe, you
have your esophagus.

00:04:21.470 --> 00:04:22.720
Let me make that
another color.

00:04:31.280 --> 00:04:33.030
And then right here
is your larynx.

00:04:37.980 --> 00:04:40.460
And I'm going to concern
ourselves with the larynx.

00:04:40.460 --> 00:04:42.440
Esophagus is where your
food goes down.

00:04:42.440 --> 00:04:44.910
We know that we eat food
with our mouth as well.

00:04:44.910 --> 00:04:46.710
So this is where we
want our food to

00:04:46.710 --> 00:04:50.310
go-- down the esophagus.

00:04:50.310 --> 00:04:52.700
But the focus of this video
is our ventilation.

00:04:52.700 --> 00:04:54.600
What do we do with our air?

00:04:54.600 --> 00:04:59.260
So I'm going to focus as the air
goes through our larynx.

00:04:59.260 --> 00:05:02.030
And the larynx is also
our voicebox.

00:05:02.030 --> 00:05:05.460
So as you hear me talking right
now, there are these

00:05:05.460 --> 00:05:08.360
little things right about here
that are vibrating at just the

00:05:08.360 --> 00:05:10.900
right frequencies and I'm able
to shape the sound with my

00:05:10.900 --> 00:05:12.330
mouth to make this video.

00:05:12.330 --> 00:05:14.340
So that's also your voicebox,
but I won't focus

00:05:14.340 --> 00:05:15.180
on that right now.

00:05:15.180 --> 00:05:17.770
It's called a voicebox because
of this whole anatomical

00:05:17.770 --> 00:05:19.580
structure that looks something
like that.

00:05:19.580 --> 00:05:22.610
But then after the air passes
through the larynx-- this is

00:05:22.610 --> 00:05:31.580
on the way in-- it goes to the
trachea, which is essentially

00:05:31.580 --> 00:05:32.830
just the pipe for air.

00:05:32.830 --> 00:05:35.170
The esophagus is the
pipe for food.

00:05:35.170 --> 00:05:36.420
Let me write this down.

00:05:40.960 --> 00:05:43.280
And then from the trachea-- and
the trachea is actually a

00:05:43.280 --> 00:05:44.590
reasonably rigid structure.

00:05:44.590 --> 00:05:46.780
It has cartilage around
it and it makes

00:05:46.780 --> 00:05:47.970
sense that it has cartilage.

00:05:47.970 --> 00:05:51.290
You don't want-- you can imagine
a hose-- if it bent a

00:05:51.290 --> 00:05:53.240
lot, you wouldn't be able to get
a lot of water through it,

00:05:53.240 --> 00:05:54.310
or a lot of air through it.

00:05:54.310 --> 00:05:56.530
So you don't want this
thing to bend a lot.

00:05:56.530 --> 00:05:58.630
So that's why it needs to have
some rigidity-- so that's why

00:05:58.630 --> 00:05:59.930
it has cartilage around it.

00:05:59.930 --> 00:06:06.090
And then it splits into two
tubes-- and I think you know

00:06:06.090 --> 00:06:08.270
where these two tubes
are going to.

00:06:08.270 --> 00:06:10.590
And I'm not drawing this
in super detail.

00:06:10.590 --> 00:06:13.410
I just want you to get the idea
of them, but these two

00:06:13.410 --> 00:06:15.770
tubes are the bronchi-- or
each one is a bronchus.

00:06:21.850 --> 00:06:24.550
And they also have cartilage,
so they're fairly rigid, but

00:06:24.550 --> 00:06:26.480
the bronchi keep splitting.

00:06:26.480 --> 00:06:31.140
They keep splitting into smaller
and smaller tubes just

00:06:31.140 --> 00:06:33.320
like that and at some point,
they stop having cartilage.

00:06:33.320 --> 00:06:35.690
They stop being reasonably
rigid, but they

00:06:35.690 --> 00:06:37.290
keep splitting off.

00:06:37.290 --> 00:06:39.030
So I'll just draw them as
these little lines.

00:06:39.030 --> 00:06:42.530
At some point they become
such thin things.

00:06:42.530 --> 00:06:44.170
They just keep splitting off.

00:06:44.170 --> 00:06:47.560
So the air just keeps splitting
off and spread and

00:06:47.560 --> 00:06:49.100
goes down the different paths.

00:06:49.100 --> 00:06:52.400
And when the bronchi no longer
have cartilage around them,

00:06:52.400 --> 00:06:53.490
they're no longer rigid.

00:06:53.490 --> 00:06:55.690
The first of those are called--
or actually all the

00:06:55.690 --> 00:06:59.480
tubes after that point are
called bronchioles.

00:06:59.480 --> 00:07:00.630
These are bronchioles.

00:07:00.630 --> 00:07:03.630
So for example, that we could
call a bronchiole.

00:07:03.630 --> 00:07:05.225
And there's nothing
fancy here.

00:07:05.225 --> 00:07:07.380
It's just a pipe that
just gets thinner

00:07:07.380 --> 00:07:08.110
and thinner and thinner.

00:07:08.110 --> 00:07:10.920
We've labeled the different
parts of the pipes different

00:07:10.920 --> 00:07:13.380
things, but the idea is, let's
take it through our mouth or

00:07:13.380 --> 00:07:16.020
our nose and we just keep
dividing and keep dividing

00:07:16.020 --> 00:07:19.310
this main division into two
different paths that takes us

00:07:19.310 --> 00:07:21.550
into each of our lungs.

00:07:21.550 --> 00:07:24.010
Let me draw this guy's
lungs here.

00:07:33.260 --> 00:07:36.590
And these bronchi-- or the
bronchi split into the lungs--

00:07:36.590 --> 00:07:39.720
the bronchioles are in the
lungs and eventually the

00:07:39.720 --> 00:07:41.660
bronchioles terminate.

00:07:41.660 --> 00:07:43.020
And this is where it
gets interesting.

00:07:43.020 --> 00:07:45.500
They keep dividing smaller and
smaller, thinner and thinner

00:07:45.500 --> 00:07:52.110
and thinner, into these little
air sacs, just like that.

00:07:52.110 --> 00:07:55.770
At the end of every super small
bronchiole are these

00:07:55.770 --> 00:07:59.500
little air sacs-- super small
air sacs-- and I'm going to

00:07:59.500 --> 00:08:02.060
talk about these air
sacs in a second.

00:08:02.060 --> 00:08:03.310
And these are called alveoli.

00:08:08.900 --> 00:08:10.700
So I've used a lot of
fancy words, but the

00:08:10.700 --> 00:08:11.860
general idea is simple.

00:08:11.860 --> 00:08:13.050
Air comes in through a pipe.

00:08:13.050 --> 00:08:15.020
The pipe gets thinner and
thinner and thinner and they

00:08:15.020 --> 00:08:16.760
end up at these little
air sacs.

00:08:16.760 --> 00:08:20.450
And you're saying, well,
how does that get the

00:08:20.450 --> 00:08:22.930
oxygen into my system?

00:08:22.930 --> 00:08:26.460
Well, the key here is that these
air sacs are super small

00:08:26.460 --> 00:08:30.950
and have very, very, very
thin walls-- or

00:08:30.950 --> 00:08:32.059
I guess thin membranes.

00:08:32.059 --> 00:08:33.700
So let me zoom in.

00:08:33.700 --> 00:08:36.740
So if I were to zoom in on one
of these alveoli-- and just to

00:08:36.740 --> 00:08:39.950
give you an idea, these are
super duper duper small.

00:08:39.950 --> 00:08:43.799
I've drawn them fairly large
here, but each alveoli-- let

00:08:43.799 --> 00:08:45.930
me draw a little bit bigger.

00:08:45.930 --> 00:08:48.780
Let me draw these air sacs.

00:08:48.780 --> 00:08:50.840
So you have these air
sacs like this.

00:08:54.030 --> 00:08:56.290
And then you have a
bronchiole that's

00:08:56.290 --> 00:08:57.600
terminating in that air sac.

00:08:57.600 --> 00:09:00.320
Maybe a bronchiole is
terminating in another air sac

00:09:00.320 --> 00:09:04.820
just like that-- another set
of air sacs just like that.

00:09:04.820 --> 00:09:10.300
Each of these are only 200 to
300 microns in diameter.

00:09:10.300 --> 00:09:13.530
So that distance right there--
let me switch colors-- that

00:09:13.530 --> 00:09:18.720
distance right there is
200 to 300 microns.

00:09:18.720 --> 00:09:22.050
And in case you don't know what
a micron is, a micron is

00:09:22.050 --> 00:09:25.200
a millionth of a meter--
or you can view it as a

00:09:25.200 --> 00:09:26.820
thousandth of a millimeter.

00:09:26.820 --> 00:09:30.340
So this is 200 thousandths
of a millimeter.

00:09:30.340 --> 00:09:32.890
Or you can think of them as--
and this is actually a very

00:09:32.890 --> 00:09:38.730
easy way to visualize it-- this
is about one fifth of a

00:09:38.730 --> 00:09:40.920
millimeter.

00:09:40.920 --> 00:09:42.790
So if I actually try to draw it
on the screen-- if you made

00:09:42.790 --> 00:09:47.600
this full screen, a millimeter
is about that far.

00:09:47.600 --> 00:09:48.690
Maybe a little farther
than that.

00:09:48.690 --> 00:09:50.130
Maybe about that far.

00:09:50.130 --> 00:09:52.530
So imagine a fifth of that and
that's what we're talking

00:09:52.530 --> 00:09:54.580
about the diameter of
one of these things.

00:09:54.580 --> 00:09:56.470
And just to put it in the
whole scheme relative to

00:09:56.470 --> 00:09:58.330
cells, the average
cell in the human

00:09:58.330 --> 00:10:00.760
body is about 10 microns.

00:10:00.760 --> 00:10:04.450
So this is only about 20 or 30
cells in diameter or relative

00:10:04.450 --> 00:10:06.600
to the average cell
in the human body.

00:10:06.600 --> 00:10:08.360
So these have a super
thin membrane.

00:10:12.180 --> 00:10:15.480
If you view them as balloons,
the balloon is very thin--

00:10:15.480 --> 00:10:20.260
pretty much one cell thick and
they're connected to the

00:10:20.260 --> 00:10:22.410
bloodflow-- or actually, a
better way to think about is

00:10:22.410 --> 00:10:26.540
that our circulatory system
passes right next to each of

00:10:26.540 --> 00:10:27.100
these things.

00:10:27.100 --> 00:10:32.580
So you have blood vessels that
come from the heart and they

00:10:32.580 --> 00:10:33.860
want to be oxygenated.

00:10:33.860 --> 00:10:37.810
In general, the blood vessels
that don't have oxygen-- and

00:10:37.810 --> 00:10:39.900
I'm going to do this in a lot
more detail when I make the

00:10:39.900 --> 00:10:43.250
videos about the heart and our
circulation system-- the blood

00:10:43.250 --> 00:10:45.570
vessels that don't have oxygen--
de-oxygenated blood

00:10:45.570 --> 00:10:46.420
is a little bit darker.

00:10:46.420 --> 00:10:47.770
It looks a little
bit purplish.

00:10:47.770 --> 00:10:49.400
So I'll draw it as blue.

00:10:49.400 --> 00:10:55.890
So these are vessels that are
coming from the heart.

00:10:55.890 --> 00:11:00.060
So this blood right here has no
oxygen in it or it's been

00:11:00.060 --> 00:11:02.650
de-oxygenated or it has very
little oxygen in it.

00:11:02.650 --> 00:11:06.520
And the word for the blood
vessels that comes from the

00:11:06.520 --> 00:11:08.010
heart are arteries.

00:11:08.010 --> 00:11:08.760
Let me write that down.

00:11:08.760 --> 00:11:11.290
I'll review that again when
we cover it in the heart.

00:11:11.290 --> 00:11:21.590
So arteries are blood vessels
from the heart.

00:11:24.220 --> 00:11:26.770
And you've probably
heard of arteries.

00:11:26.770 --> 00:11:29.190
Vessels that go to the heart
are called veins.

00:11:36.010 --> 00:11:39.160
This is really important to keep
in mind because later on,

00:11:39.160 --> 00:11:42.270
you're going to see that
arteries don't always carry

00:11:42.270 --> 00:11:45.100
oxygen or they're always not
de-oxygenated and veins always

00:11:45.100 --> 00:11:45.900
aren't one way or the other.

00:11:45.900 --> 00:11:47.520
We're going to go into a lot
more detail when we actually

00:11:47.520 --> 00:11:49.780
cover the heart and the
circulatory system, but just

00:11:49.780 --> 00:11:51.630
remember, arteries go away.

00:11:51.630 --> 00:11:53.510
Veins go to the heart.

00:11:53.510 --> 00:11:58.610
So here, these are arteries
going away from the heart to

00:11:58.610 --> 00:12:03.020
the lungs, to the alveoli
because they want the blood

00:12:03.020 --> 00:12:05.310
that's traveling in them
to get oxygen.

00:12:05.310 --> 00:12:09.720
So what's going to happen is
that the air is flowing

00:12:09.720 --> 00:12:16.060
through the bronchioles and
circulating around the

00:12:16.060 --> 00:12:20.650
alveoli, filling the alveoli--
and as they fill the alveoli,

00:12:20.650 --> 00:12:27.680
the little molecules of oxygen
are allowed to cross the

00:12:27.680 --> 00:12:30.220
membrane of the alveoli
and essentially be

00:12:30.220 --> 00:12:31.530
absorbed into the blood.

00:12:31.530 --> 00:12:33.850
I'll do a lot more on that when
we talk about hemoglobin

00:12:33.850 --> 00:12:35.740
and red blood cells, but you
just have to realize that

00:12:35.740 --> 00:12:38.920
there's just a lot
of capillaries.

00:12:38.920 --> 00:12:41.810
Capillaries are just super small
blood vessels that allow

00:12:41.810 --> 00:12:44.850
air to pass-- essentially oxygen
and carbon dioxide

00:12:44.850 --> 00:12:46.560
molecules to pass
between them.

00:12:46.560 --> 00:12:48.580
These have a lot of capillaries
on them that allow

00:12:48.580 --> 00:12:51.450
the exchange of gases.

00:12:51.450 --> 00:12:56.470
So the oxygen can go into this
blood and so once the oxygen--

00:12:56.470 --> 00:13:00.310
so this is the vessel that's
coming from the heart and then

00:13:00.310 --> 00:13:01.100
it's just a tube.

00:13:01.100 --> 00:13:03.710
So then once it gets the oxygen,
it's going to go back

00:13:03.710 --> 00:13:04.960
to the heart.

00:13:09.890 --> 00:13:13.790
And so essentially this is the
point where this vessel, this

00:13:13.790 --> 00:13:16.840
pipe, part of our circulatory
system, goes from being an

00:13:16.840 --> 00:13:19.745
artery-- because it's coming
from the heart-- to a vein

00:13:19.745 --> 00:13:22.320
because it's going back
to the heart.

00:13:22.320 --> 00:13:26.010
And there's a special word for
these arteries and veins.

00:13:26.010 --> 00:13:28.900
They're called pulmonary
arteries and veins.

00:13:28.900 --> 00:13:34.980
So going away from the heart to
the lungs, to the alveoli,

00:13:34.980 --> 00:13:40.840
these are the pulmonary
arteries.

00:13:40.840 --> 00:13:44.775
And going back to the heart
are the pulmonary veins.

00:13:49.800 --> 00:13:53.090
Now you're saying, Sal, what
does pulmonary mean?

00:13:53.090 --> 00:13:55.920
Well, pulmo comes from the
Latin for the lungs.

00:13:55.920 --> 00:13:59.090
It literally means the arteries
that are of the lungs

00:13:59.090 --> 00:14:01.380
or that go to the lungs
and the veins that

00:14:01.380 --> 00:14:02.300
come from the lungs.

00:14:02.300 --> 00:14:04.840
So anytime people talk about
pulmonary anything, they're

00:14:04.840 --> 00:14:09.200
talking about our lungs-- or
maybe something related to how

00:14:09.200 --> 00:14:09.770
we breathe.

00:14:09.770 --> 00:14:13.200
So it's a good word to know.

00:14:13.200 --> 00:14:19.300
So anyway, you have your oxygen
coming in through your

00:14:19.300 --> 00:14:22.670
mouth or your nose, through the
pharynx-- it could fill

00:14:22.670 --> 00:14:23.200
your stomach.

00:14:23.200 --> 00:14:25.550
We can blow up our stomach
like a balloon, but that

00:14:25.550 --> 00:14:29.150
doesn't help us actually get
oxygen to our blood stream.

00:14:29.150 --> 00:14:32.990
But the oxygen will come through
our larynx, into our

00:14:32.990 --> 00:14:36.270
trachea, through the bronchi,
eventually in bronchioles,

00:14:36.270 --> 00:14:40.120
ending up in alveoli and being
able to be absorbed into what

00:14:40.120 --> 00:14:42.570
where the arteries, but then
we're going to go back and

00:14:42.570 --> 00:14:44.490
then essentially oxygenate
the blood.

00:14:44.490 --> 00:14:50.140
The red blood cells become red
once the hemoglobin becomes

00:14:50.140 --> 00:14:53.980
very red or scarlet once it
actually has the oxygen and

00:14:53.980 --> 00:14:55.300
then we go back.

00:14:55.300 --> 00:14:58.140
But at the same time, this
isn't just about getting

00:14:58.140 --> 00:15:01.850
oxygen into our arteries
or onto the hemoglobin.

00:15:01.850 --> 00:15:05.110
It's also about releasing
carbon dioxide.

00:15:05.110 --> 00:15:10.610
So these blue arteries coming
from the lungs are also going

00:15:10.610 --> 00:15:14.730
to release carbon dioxide
into the alveoli.

00:15:14.730 --> 00:15:16.560
And these will be exhaled.

00:15:16.560 --> 00:15:18.360
So we have oxygen coming in.

00:15:21.970 --> 00:15:24.110
Other things will be coming in,
but the O2 is what gets

00:15:24.110 --> 00:15:25.790
absorbed in the alveoli.

00:15:25.790 --> 00:15:30.680
And then when we breathe out,
we're going to have carbon

00:15:30.680 --> 00:15:33.850
dioxide that was in our blood,
but then it gets absorbed into

00:15:33.850 --> 00:15:35.840
the alveoli and they
get squeezed out.

00:15:35.840 --> 00:15:37.685
I'm going to tell you in a
second how it gets squeezed.

00:15:43.320 --> 00:15:46.120
It's actually that squeezing out
that actually-- when the

00:15:46.120 --> 00:15:51.160
air goes back out, it can
vibrate my vocal cords and

00:15:51.160 --> 00:15:53.210
it'll allow me to talk, but I'm
not going to go into too

00:15:53.210 --> 00:15:54.620
much detail about that.

00:15:54.620 --> 00:15:58.200
So the last thing to consider
about this whole pulmonary

00:15:58.200 --> 00:16:04.360
system or about our lungs is,
how does it force the air in

00:16:04.360 --> 00:16:06.690
and how does it force
the air out?

00:16:06.690 --> 00:16:09.660
And the way it's done is really
kind of like a-- you

00:16:09.660 --> 00:16:12.700
could imagine it's kind of a
pump or a balloon-- is that we

00:16:12.700 --> 00:16:15.680
have this huge layer
of flat muscles.

00:16:15.680 --> 00:16:17.170
Let me pick a good color here.

00:16:25.860 --> 00:16:27.400
Right below the lungs--
and this is

00:16:27.400 --> 00:16:28.650
called a thoracic diaphragm.

00:16:38.320 --> 00:16:41.280
And so when it's relaxed, it
kind of has this arch shape,

00:16:41.280 --> 00:16:43.700
and so the lungs are kind
of squeezed in.

00:16:43.700 --> 00:16:45.440
They don't have a
lot of volume.

00:16:45.440 --> 00:16:49.380
But when I essentially breathe
in, what's happening is this

00:16:49.380 --> 00:16:52.170
thoracic diaphragm is contracted
and when it's

00:16:52.170 --> 00:16:55.950
contracted, it gets shorter, but
more importantly, it opens

00:16:55.950 --> 00:17:00.440
up the space where
my lungs are.

00:17:00.440 --> 00:17:02.330
So my lungs can fill
up that space.

00:17:02.330 --> 00:17:04.920
So what it does is, it
essentially-- it's like

00:17:04.920 --> 00:17:07.420
pulling a balloon larger,
making the

00:17:07.420 --> 00:17:10.064
volume of my lungs larger.

00:17:10.064 --> 00:17:13.310
And when you make the volume of
something larger-- so the

00:17:13.310 --> 00:17:16.000
lungs will become larger as
my thoracic diaphragm is

00:17:16.000 --> 00:17:18.630
contracted and it kind of arches
down, creates more

00:17:18.630 --> 00:17:22.150
space-- and as the volume of
something becomes larger, the

00:17:22.150 --> 00:17:24.140
pressure inside of
them goes down.

00:17:24.140 --> 00:17:26.420
If you remember from physics,
the pressure

00:17:26.420 --> 00:17:27.720
times volume is a constant.

00:17:31.280 --> 00:17:39.050
So when we breathe in, our brain
is essentially telling

00:17:39.050 --> 00:17:40.300
our diaphragm to contract.

00:17:48.550 --> 00:17:51.125
We have more space
around our lungs.

00:17:51.125 --> 00:17:56.390
Our lungs expand to
fill the space.

00:17:56.390 --> 00:17:59.870
We have less pressure here than
we have outside-- or you

00:17:59.870 --> 00:18:01.540
can view it as negative
pressure.

00:18:01.540 --> 00:18:04.440
So air always wants to go from
high pressure to low pressure

00:18:04.440 --> 00:18:07.060
and so air is going to
flow into our lungs.

00:18:07.060 --> 00:18:10.710
And hopefully there'll be some
oxygen there that can then

00:18:10.710 --> 00:18:13.530
essentially go into our alveoli
and end up in our

00:18:13.530 --> 00:18:17.190
arteries and then go back in the
veins as oxygen attached

00:18:17.190 --> 00:18:17.820
to hemoglobin.

00:18:17.820 --> 00:18:19.530
I'll talk more about
that in detail.

00:18:19.530 --> 00:18:21.960
And then when we stop
contracting the diaphragm, it

00:18:21.960 --> 00:18:23.980
goes back to this
arched position.

00:18:23.980 --> 00:18:25.020
It contracts.

00:18:25.020 --> 00:18:26.550
It's kind of like
a rubber band.

00:18:26.550 --> 00:18:30.480
It contracts back the lungs and
it essentially expels the

00:18:30.480 --> 00:18:33.780
air back and now that air's
going to have a lot more

00:18:33.780 --> 00:18:35.120
carbon dioxide.

00:18:35.120 --> 00:18:39.130
And just to get a sense of-- I
can look at my lungs-- I can't

00:18:39.130 --> 00:18:42.130
look at them, but they
don't seem too large.

00:18:42.130 --> 00:18:45.350
How do I get enough oxygen in
them-- and the key is, is that

00:18:45.350 --> 00:18:52.090
because of this branching
process and the alveoli, the

00:18:52.090 --> 00:18:55.920
inside surface area of the lungs
are actually much larger

00:18:55.920 --> 00:18:59.310
than you can imagine-- or
actually than I could have

00:18:59.310 --> 00:19:01.830
imagined had someone
not told me.

00:19:01.830 --> 00:19:04.090
So it actually turns out-- I
looked it up-- the internal

00:19:04.090 --> 00:19:08.650
surface area of your alveoli--
so the total surface area

00:19:08.650 --> 00:19:11.470
where the oxygen can be absorbed
in or the carbon

00:19:11.470 --> 00:19:13.950
dioxide can be absorbed out from
the blood-- it's actually

00:19:13.950 --> 00:19:18.610
75 square meters.

00:19:18.610 --> 00:19:19.910
That's meters, not feet.

00:19:22.470 --> 00:19:24.730
If you think about it, that's
like a-- imagine some type of

00:19:24.730 --> 00:19:26.310
a tarp or a field.

00:19:26.310 --> 00:19:29.930
That's almost nine
by nine meters.

00:19:29.930 --> 00:19:36.340
That's almost 27 by
27 square feet.

00:19:36.340 --> 00:19:38.530
That's the size of some
people's backyards.

00:19:38.530 --> 00:19:41.140
That's how much surface air you
have inside of your lungs.

00:19:41.140 --> 00:19:42.240
It's all folded up.

00:19:42.240 --> 00:19:45.310
That's how it gets jammed into
what look like relatively

00:19:45.310 --> 00:19:46.220
small lungs.

00:19:46.220 --> 00:19:48.410
But that's what gives us enough
surface area for enough

00:19:48.410 --> 00:19:51.680
of the air, enough of the
oxygen, to cross the alveoli

00:19:51.680 --> 00:19:54.980
membrane into our blood system
and enough of the carbon

00:19:54.980 --> 00:19:56.560
dioxide to go back in.

00:19:56.560 --> 00:19:59.370
And just to have a sense of how
many alveoli we had-- I

00:19:59.370 --> 00:20:02.240
told you that they're very
small-- we actually have 300

00:20:02.240 --> 00:20:04.410
million in each lung.

00:20:04.410 --> 00:20:09.350
In each lung, we have
300 million alveoli.

00:20:09.350 --> 00:20:12.020
So anyway, hopefully that gives
you a decent sense of

00:20:12.020 --> 00:20:16.230
how we at least get oxygen
into our blood system and

00:20:16.230 --> 00:20:17.640
carbon dioxide out of it.

00:20:17.640 --> 00:20:20.200
In the next video, I'll talk
more about our actual

00:20:20.200 --> 00:20:26.520
circulatory system and how we
get the oxygen from the lungs

00:20:26.520 --> 00:20:28.240
to the rest of the body and
how do we get the carbon

00:20:28.240 --> 00:20:31.640
dioxide from the rest of the
body into the lungs?