MBBS Exam > MBBS Videos > Red blood cells
Red blood cells Video Lecture - MBBS
FAQs on Red blood cells
| 1. What are red blood cells? |  |
Ans. Red blood cells, also known as erythrocytes, are the most common type of blood cells in the human body. They are responsible for transporting oxygen from the lungs to all tissues of the body and carrying carbon dioxide back to the lungs for exhalation.
| 2. How are red blood cells formed? | |
Ans. Red blood cells are formed through a process called erythropoiesis, which occurs in the bone marrow. Stem cells in the bone marrow differentiate into red blood cells under the influence of a hormone called erythropoietin, which is released by the kidneys in response to low oxygen levels in the blood.
| 3. What is the lifespan of red blood cells? | |
Ans. The average lifespan of red blood cells is approximately 120 days. After this period, old and damaged red blood cells are removed from circulation by the spleen and liver, and new red blood cells are continuously produced to replace them.
| 4. Can red blood cells reproduce? | |
Ans. Unlike other cells in the body, red blood cells do not contain a nucleus and therefore cannot reproduce or divide. They are produced in the bone marrow and have a limited lifespan before being eliminated from the circulation.
| 5. What happens if the body doesn't produce enough red blood cells? | |
Ans. A decrease in the production of red blood cells can lead to a condition called anemia. Anemia can result in symptoms such as fatigue, weakness, shortness of breath, pale skin, and an increased heart rate. It can be caused by various factors, including nutritional deficiencies, chronic diseases, or bone marrow disorders. Treatment options depend on the underlying cause and may include dietary changes, iron supplements, or medications.
Text Transcript from Video
In the last video on the lungs
or the gas exchange in our
bodies or on the pulmonary
system, we left off with the
alveolar sacs.
Let me draw one right here.
So we have these alveolar sacs
that I talked about and
they're in these little
clumps like this.
Let me draw a couple of them
just so you get the idea.
And if you remember from the
last video, these are kind of
where air goes in through our
trachea, then that splits up
into our bronchi, and then
those split into the
bronchioles, and
the bronchioles
terminate at these alveoli.
So that's the alveoli.
These are these super-small sacs
that we talked about in
the last video on the
pulmonary system.
You might want to watch
that video if none
of this sounds familiar.
And then of course we have our
bronchiole that feeds into
this, and then that might have
branched off from another one
that feeds into another set of
alveolar sacs, but I don't
want to get too focused
on that.
I covered that in
the last video.
In the last video, we saw that
air, when we breathe in, when
our diaphragm contracts and
makes our lungs expand and
fill up that space,
air comes in.
Air comes in and that air that
comes in is going to be-- as
we're breathing atmospheric
air-- it's going to be 21%
oxygen and it's going
to be 78% nitrogen.
And actually, in our atmosphere,
carbon dioxide is
actually almost a trace gas.
It's less than 1%.
So any time you breathe in on
Earth, this is what you're
going to get.
And we said in the last video
that you have these
capillaries, these pulmonary
capillaries that are running
all along the side
of these alveoli.
So let me draw those pulmonary
capillaries-- and so when they
are de-oxygenated-- so they come
here to be oxygenated.
So when they're de-oxygenated,
they might
look a little purplish.
And then they pick up the
oxygen from inside the
alveoli-- or the oxygen diffuses
across the membrane
of the alveoli, into these
capillaries, into these super
small tubes.
And then once they do, that
makes the blood red.
I'm going to talk in a little
bit about why it becomes red.
So then it becomes red, and now
that the blood is red, it
has its oxygen.
The whole point is to
get the oxygen.
It's ready to go back
to the heart.
So that's just one little
part of it.
And we learned in the last video
that something that goes
away from the heart-- so this is
going away from the heart--
that is an artery. "A
for Away" - Artery.
And something that's going
towards the heart is a vein.
So this right here is a vein.
Now one question-- and
this actually came
up in the last video.
Someone asked-- which I think is
a very good question-- is,
gee, when we breathe in, most
of the air is nitrogen.
Only 21% is oxygen.
What happens to all that
nitrogen there?
How come that doesn't
go into our blood?
And that's actually an
excellent question.
So to answer that, I think that
actually helps explain
what's going on here.
Let's draw a little
bit bigger.
This is the inside of
of an alveolus.
This is its membrane right here,
super thin, almost one
cell thick.
And then you have a capillary
running right next to it.
Let me do that in
a neutral color.
So you have a capillary
that's maybe running
right along the surface.
And this is porous to gases
like oxygen, and nitrogen,
carbon dioxide.
And what we have here-- let's
say that this is-- so the
heart is over here.
So this is blood coming from
the heart and then this is
going to go back to the heart.
Well, the heart's
on both sides.
So let me write it this way.
From the heart and
to the heart.
And what you have here is--
when we're coming from the
heart, this is de-oxygenated
blood and it's actually going
to have a high concentration
of carbon dioxide.
I already did nitrogen
as green.
Let me do carbon dioxide
as orange.
There's a lot of carbon dioxide
and actually carbon
dioxide actually gets diffused
in the blood.
It actually is carried in
the plasma of the blood.
It's not carried by red blood
cells that we're going to talk
about in a second.
So that's a bunch of carbon
dioxide here.
And the concentration of
carbon dioxide in the
de-oxygenated blood is going
to be higher than the
concentration of carbon dioxide
in the alveolus.
so if this is porous to carbon
dioxide, this membrane-- and
it is, these carbon dioxide
molecules are going to diffuse
into the alveolus.
Now on the other side of that--
we have oxygen here.
We're breathing it in.
The air is 21% oxygen so you're
actually going to have
a lot more oxygen than
carbon dioxide.
And this is de-oxygenated
blood.
We used all of the oxygen in our
body and we'll talk more
about that either at the end of
this video or in a future
video on how we use it or where
it goes in our body, but
there's no oxygen here so the
oxygen is going to be taken--
it's going to diffuse across
this membrane because the
concentration of
oxygen is low.
Now the question is-- so
immediately you see that as
the oxygen diffuses across
this membrane, all of a
sudden, this is oxygenated
blood ready to
go back to the heart.
So this transition between
artery and vein is a very
subtle thing.
Very clearly here, you
say that, OK, this is
going from the heart.
This is our vein.
This is going to the
heart-- sorry.
I always get confused.
This is going away from the
heart-- and I was looking for
an A and I wrote from.
This is away from the heart
so this is an artery.
And this is going to the heart
so this is a vein.
So you could make
the division.
You could say, OK, once it's
oxygenated, maybe we're going
back to the heart, but it's kind
of an arbitrary-- sorry.
I spelled artery wrong.
These are my flaws.
Spelling was never
my strong suit.
So it's hard to say where
the artery ends
and the vein begins.
A good demarcation is when the
carbon dioxide concentration
goes low and that the oxygen
concentration goes high.
That's a good time, where
we start from
the pulmonary artery.
Probably in the next video, I
will a make a very-- you'll
see why the pulmonary arteries
are special, because pulmonary
arteries coming away from the
heart have no oxygen or very
little oxygen and they have
a lot of carbon dioxide.
So pulmonary veins, which is--
it's arbitrary where the
artery turns into a vein.
Once it gets oxygenated, it's
ready to go back to the heart.
It's a pulmonary vein and
it is oxygenated.
So it has oxygenated-- and we
could write de-oxygenated.
Now the reason why I say it's
special besides the fact that
pulmonary arteries and veins go
to and from the lungs, is
that they're kind
of the opposite.
Because in the rest of the body
when we're going away
from the heart or we're talking
about arteries, you're
going to see that that's
oxygenated blood, while when
we're going away from the heart
to the lungs, that's
de-oxygenated blood.
Similarly in the rest of the
body, when we're going to the
heart, where you're to see
that that's de-oxygenated
blood, but in the pulmonary
vein, when we're going to the
heart, it's oxygenated because
the lungs are what take up the
carbon dioxide and give
us the oxygen.
Now I still haven't answered
that interesting question that
rose on the message board
on the last video.
What happens to the 78% of
nitrogen that's sitting here?
There's just a ton of nitrogen
over here, more than the
oxygen, a lot more than
the carbon dioxide.
What happens to all of these
nitrogen molecules?
And the answer is, nitrogen can
diffuse and does diffuse
into the blood, but the blood's
ability to take in
nitrogen isn't that high.
And you might say, well,
why is oxygen special?
Why can the blood take
up oxygen so
much easier than nitrogen?
And that's where the red blood
cells come into play.
Let me write this down.
I'll write it in red.
Red blood cells, which
are fascinating on a
whole set of levels.
What red blood cells-- these
are these cells that are
sitting in-- they're flowing
through our circulatory system
and they look kind of
like lozenges, if I
were to draw one.
They're kind of like a flattened
sphere with a little
divot on either side of it--
a lot like a lozenge.
So if I were to draw it from
the side, it might look
something like-- well, from the
side, it would look like
that and if you could see
through it, there'd be a
little divot on each side.
If I were to draw it at an
angle, it would look
something like this.
There'd be a little divot on
that side and there'd be a
similar divot on
the other side.
And red blood cells-- and I
could do a whole set of videos
just on red blood cells--
they contain hemoglobin.
Maybe we'll do a whole
video on hemoglobin.
The hemoglobin are these
small proteins that
contain four hem groups.
So inside of red blood cells,
you have millions of
hemoglobin proteins.
And the hemoglobin proteins--
I'll just draw them as this--
they have these four
heme groups.
And heme groups, the main
component is iron.
And that's why iron
is so important.
If you don't have enough iron,
you're going to have trouble
processing oxygen in your blood
and your hemoglobin
won't be functional enough.
But it has iron on it.
It has four of these
heme groups.
And each of these heme groups
can bond to oxygen molecules.
They're very good binders
of oxygen.
And we're going to see in a
little bit-- probably the next
video-- how they release the
oxygen, but this has tons,
this has millions of heme groups
in it and the oxygen
diffuses across the membrane
of the red blood cells and
bonds to to the heme groups
on your hemoglobin.
So because the red blood cells
have the hemoglobin inside of
them, they're like these sponges
for oxygen because
hemoglobin is so good
at taking in oxygen.
So the red blood cells are able
to essentially suck up
all of the oxygen out
of the plasma.
The plasma we can view as just
the general fluid of the
blood, not including the
red blood cells.
So the red blood cell
here isn't so red.
And the reason-- and this is the
key point-- the reason why
it's not so red-- maybe we had
a red blood cell over here--
let me make it clear.
Carbon dioxide for
the most part is
traveling within the plasma.
It gets absorbed into the actual
fluid and I'll talk
about it in a future video.
It's actually in a slightly
different form.
It's as carbonic acid and that's
actually a key point
for how the plasma knows where
to dump the oxygen, but I'll
talk about that in
a future video.
But over here, this red blood
cell has a bunch of hemoglobin
proteins in it, but those
hemoglobin proteins have
dumped their oxygen.
And it actually turns out it's
the hemoglobin-- so with
oxygen, hemoglobin looks red.
It reflects red light.
When it doesn't have oxygen,
hemoglobin does not look red.
It looks kind of purplish,
bluish, darkish-- something.
And that's why in most of your
body, your veins that have
de-oxygenated red blood cells
look kind of bluish.
And the reason why it changes
color is that when the oxygen
bonds to the hem sites on the
hemoglobin, it actually
changes the entire confirmation,
the entire
structure of the protein.
We've see that multiple times.
The whole protein folds in
such a way that all of a
sudden, instead of purplish or
dark light being reflected,
now red light is reflected.
And that's why red blood cells
will become red once they take
the oxygen.
But I'm going on a tangent.
The whole point here is saying,
why we taking up so
much more oxygen than nitrogen,
given that there's
less oxygen in the atmosphere
than nitrogen?
And the key is these
red blood cells.
These red blood cells have these
millions of hemoglobin
proteins inside of them and they
take them up and they sop
up all of the oxygen
out of the plasma.
Actually, they sop about
98.5% of the oxygen.
So these red blood cells are
just traveling and they're
going to go back to the heart.
They are what make
our blood red.
So you have this thing,
hemoglobin, that's sitting in
red blood cells.
It's sopping up all
the oxygen.
So it keeps the oxygen
concentration and the actual
plasma low.
You have nothing like
that for nitrogen.
There is no cell that's sopping
up the nitrogen.
Nitrogen does not bond
to hemoglobin.
So that's why oxygen
is taken up so
much better than nitrogen.
It's a very interesting question
because if you just
think about how much nitrogen
is, it's kind of a very
natural idea.
Now I want to focus a little
bit on the red blood cell
itself because it's
fascinating.
In the video on the structure
of the cell, I start off
saying, all cells have
a membrane and
they all have DNA.
Now, the fascinating thing about
a red blood cell-- I
already said it has millions
of hemoglobin molecules or
proteins inside of it.
The fascinating thing
about a red blood
cell-- it has no nucleus.
And no DNA.
This is mind boggling when
I first found out.
I was like, well, why
is it a cell?
Is it really even
a living thing?
And it turns out when
it's growing,
it does have a nucleus.
All cells need a nucleus with
DNA in order to generate the
proteins that build it up,
in order to exist and
structurally make itself the way
it needs to be made, but
the whole point of a red blood
cell is to contain as much
hemoglobin as possible.
And so you can imagine, this
is actually a favorable
evolutionary trait, that as red
blood cells are ready to
go into business, you've built
the whole structure, they
actually get rid of
their nucleus.
They actually push their nucleus
out of the cell and
the whole reason why that's
beneficial is, that's more
space for hemoglobin.
Because the more hemoglobin you
have, the more oxygen you
can take up.
And I can do a ton of videos
on hemoglobin and all of
that-- and actually, I'm going
to do a lot more on the
circulatory system so don't
worry about that, but I want
to go over one other really
interesting thing about
hemoglobin.
We already talked about
red blood cells.
I think it's fascinating that
they actually don't have a
nucleus in their mature form.
They actually have
very short lives.
They live maybe 80, 120 days
so they're not these long
lived cells-- so it's almost
a philosophical question.
Are are they still alive once
they've lost their DNA or are
they just vessels for oxygen
that aren't really alive
because they aren't regenerating
and producing
their own DNA?
So actually, instead of going
into the hemoglobin discussion
right now, I'll leave you
there in this video.
I realize I've been making
20-minute videos where my goal
is really to make
ten-minute ones.
So I'll leave you here and in
the next video, we'll talk
more about hemoglobin and
the circulatory system.
or the gas exchange in our
bodies or on the pulmonary
system, we left off with the
alveolar sacs.
Let me draw one right here.
So we have these alveolar sacs
that I talked about and
they're in these little
clumps like this.
Let me draw a couple of them
just so you get the idea.
And if you remember from the
last video, these are kind of
where air goes in through our
trachea, then that splits up
into our bronchi, and then
those split into the
bronchioles, and
the bronchioles
terminate at these alveoli.
So that's the alveoli.
These are these super-small sacs
that we talked about in
the last video on the
pulmonary system.
You might want to watch
that video if none
of this sounds familiar.
And then of course we have our
bronchiole that feeds into
this, and then that might have
branched off from another one
that feeds into another set of
alveolar sacs, but I don't
want to get too focused
on that.
I covered that in
the last video.
In the last video, we saw that
air, when we breathe in, when
our diaphragm contracts and
makes our lungs expand and
fill up that space,
air comes in.
Air comes in and that air that
comes in is going to be-- as
we're breathing atmospheric
air-- it's going to be 21%
oxygen and it's going
to be 78% nitrogen.
And actually, in our atmosphere,
carbon dioxide is
actually almost a trace gas.
It's less than 1%.
So any time you breathe in on
Earth, this is what you're
going to get.
And we said in the last video
that you have these
capillaries, these pulmonary
capillaries that are running
all along the side
of these alveoli.
So let me draw those pulmonary
capillaries-- and so when they
are de-oxygenated-- so they come
here to be oxygenated.
So when they're de-oxygenated,
they might
look a little purplish.
And then they pick up the
oxygen from inside the
alveoli-- or the oxygen diffuses
across the membrane
of the alveoli, into these
capillaries, into these super
small tubes.
And then once they do, that
makes the blood red.
I'm going to talk in a little
bit about why it becomes red.
So then it becomes red, and now
that the blood is red, it
has its oxygen.
The whole point is to
get the oxygen.
It's ready to go back
to the heart.
So that's just one little
part of it.
And we learned in the last video
that something that goes
away from the heart-- so this is
going away from the heart--
that is an artery. "A
for Away" - Artery.
And something that's going
towards the heart is a vein.
So this right here is a vein.
Now one question-- and
this actually came
up in the last video.
Someone asked-- which I think is
a very good question-- is,
gee, when we breathe in, most
of the air is nitrogen.
Only 21% is oxygen.
What happens to all that
nitrogen there?
How come that doesn't
go into our blood?
And that's actually an
excellent question.
So to answer that, I think that
actually helps explain
what's going on here.
Let's draw a little
bit bigger.
This is the inside of
of an alveolus.
This is its membrane right here,
super thin, almost one
cell thick.
And then you have a capillary
running right next to it.
Let me do that in
a neutral color.
So you have a capillary
that's maybe running
right along the surface.
And this is porous to gases
like oxygen, and nitrogen,
carbon dioxide.
And what we have here-- let's
say that this is-- so the
heart is over here.
So this is blood coming from
the heart and then this is
going to go back to the heart.
Well, the heart's
on both sides.
So let me write it this way.
From the heart and
to the heart.
And what you have here is--
when we're coming from the
heart, this is de-oxygenated
blood and it's actually going
to have a high concentration
of carbon dioxide.
I already did nitrogen
as green.
Let me do carbon dioxide
as orange.
There's a lot of carbon dioxide
and actually carbon
dioxide actually gets diffused
in the blood.
It actually is carried in
the plasma of the blood.
It's not carried by red blood
cells that we're going to talk
about in a second.
So that's a bunch of carbon
dioxide here.
And the concentration of
carbon dioxide in the
de-oxygenated blood is going
to be higher than the
concentration of carbon dioxide
in the alveolus.
so if this is porous to carbon
dioxide, this membrane-- and
it is, these carbon dioxide
molecules are going to diffuse
into the alveolus.
Now on the other side of that--
we have oxygen here.
We're breathing it in.
The air is 21% oxygen so you're
actually going to have
a lot more oxygen than
carbon dioxide.
And this is de-oxygenated
blood.
We used all of the oxygen in our
body and we'll talk more
about that either at the end of
this video or in a future
video on how we use it or where
it goes in our body, but
there's no oxygen here so the
oxygen is going to be taken--
it's going to diffuse across
this membrane because the
concentration of
oxygen is low.
Now the question is-- so
immediately you see that as
the oxygen diffuses across
this membrane, all of a
sudden, this is oxygenated
blood ready to
go back to the heart.
So this transition between
artery and vein is a very
subtle thing.
Very clearly here, you
say that, OK, this is
going from the heart.
This is our vein.
This is going to the
heart-- sorry.
I always get confused.
This is going away from the
heart-- and I was looking for
an A and I wrote from.
This is away from the heart
so this is an artery.
And this is going to the heart
so this is a vein.
So you could make
the division.
You could say, OK, once it's
oxygenated, maybe we're going
back to the heart, but it's kind
of an arbitrary-- sorry.
I spelled artery wrong.
These are my flaws.
Spelling was never
my strong suit.
So it's hard to say where
the artery ends
and the vein begins.
A good demarcation is when the
carbon dioxide concentration
goes low and that the oxygen
concentration goes high.
That's a good time, where
we start from
the pulmonary artery.
Probably in the next video, I
will a make a very-- you'll
see why the pulmonary arteries
are special, because pulmonary
arteries coming away from the
heart have no oxygen or very
little oxygen and they have
a lot of carbon dioxide.
So pulmonary veins, which is--
it's arbitrary where the
artery turns into a vein.
Once it gets oxygenated, it's
ready to go back to the heart.
It's a pulmonary vein and
it is oxygenated.
So it has oxygenated-- and we
could write de-oxygenated.
Now the reason why I say it's
special besides the fact that
pulmonary arteries and veins go
to and from the lungs, is
that they're kind
of the opposite.
Because in the rest of the body
when we're going away
from the heart or we're talking
about arteries, you're
going to see that that's
oxygenated blood, while when
we're going away from the heart
to the lungs, that's
de-oxygenated blood.
Similarly in the rest of the
body, when we're going to the
heart, where you're to see
that that's de-oxygenated
blood, but in the pulmonary
vein, when we're going to the
heart, it's oxygenated because
the lungs are what take up the
carbon dioxide and give
us the oxygen.
Now I still haven't answered
that interesting question that
rose on the message board
on the last video.
What happens to the 78% of
nitrogen that's sitting here?
There's just a ton of nitrogen
over here, more than the
oxygen, a lot more than
the carbon dioxide.
What happens to all of these
nitrogen molecules?
And the answer is, nitrogen can
diffuse and does diffuse
into the blood, but the blood's
ability to take in
nitrogen isn't that high.
And you might say, well,
why is oxygen special?
Why can the blood take
up oxygen so
much easier than nitrogen?
And that's where the red blood
cells come into play.
Let me write this down.
I'll write it in red.
Red blood cells, which
are fascinating on a
whole set of levels.
What red blood cells-- these
are these cells that are
sitting in-- they're flowing
through our circulatory system
and they look kind of
like lozenges, if I
were to draw one.
They're kind of like a flattened
sphere with a little
divot on either side of it--
a lot like a lozenge.
So if I were to draw it from
the side, it might look
something like-- well, from the
side, it would look like
that and if you could see
through it, there'd be a
little divot on each side.
If I were to draw it at an
angle, it would look
something like this.
There'd be a little divot on
that side and there'd be a
similar divot on
the other side.
And red blood cells-- and I
could do a whole set of videos
just on red blood cells--
they contain hemoglobin.
Maybe we'll do a whole
video on hemoglobin.
The hemoglobin are these
small proteins that
contain four hem groups.
So inside of red blood cells,
you have millions of
hemoglobin proteins.
And the hemoglobin proteins--
I'll just draw them as this--
they have these four
heme groups.
And heme groups, the main
component is iron.
And that's why iron
is so important.
If you don't have enough iron,
you're going to have trouble
processing oxygen in your blood
and your hemoglobin
won't be functional enough.
But it has iron on it.
It has four of these
heme groups.
And each of these heme groups
can bond to oxygen molecules.
They're very good binders
of oxygen.
And we're going to see in a
little bit-- probably the next
video-- how they release the
oxygen, but this has tons,
this has millions of heme groups
in it and the oxygen
diffuses across the membrane
of the red blood cells and
bonds to to the heme groups
on your hemoglobin.
So because the red blood cells
have the hemoglobin inside of
them, they're like these sponges
for oxygen because
hemoglobin is so good
at taking in oxygen.
So the red blood cells are able
to essentially suck up
all of the oxygen out
of the plasma.
The plasma we can view as just
the general fluid of the
blood, not including the
red blood cells.
So the red blood cell
here isn't so red.
And the reason-- and this is the
key point-- the reason why
it's not so red-- maybe we had
a red blood cell over here--
let me make it clear.
Carbon dioxide for
the most part is
traveling within the plasma.
It gets absorbed into the actual
fluid and I'll talk
about it in a future video.
It's actually in a slightly
different form.
It's as carbonic acid and that's
actually a key point
for how the plasma knows where
to dump the oxygen, but I'll
talk about that in
a future video.
But over here, this red blood
cell has a bunch of hemoglobin
proteins in it, but those
hemoglobin proteins have
dumped their oxygen.
And it actually turns out it's
the hemoglobin-- so with
oxygen, hemoglobin looks red.
It reflects red light.
When it doesn't have oxygen,
hemoglobin does not look red.
It looks kind of purplish,
bluish, darkish-- something.
And that's why in most of your
body, your veins that have
de-oxygenated red blood cells
look kind of bluish.
And the reason why it changes
color is that when the oxygen
bonds to the hem sites on the
hemoglobin, it actually
changes the entire confirmation,
the entire
structure of the protein.
We've see that multiple times.
The whole protein folds in
such a way that all of a
sudden, instead of purplish or
dark light being reflected,
now red light is reflected.
And that's why red blood cells
will become red once they take
the oxygen.
But I'm going on a tangent.
The whole point here is saying,
why we taking up so
much more oxygen than nitrogen,
given that there's
less oxygen in the atmosphere
than nitrogen?
And the key is these
red blood cells.
These red blood cells have these
millions of hemoglobin
proteins inside of them and they
take them up and they sop
up all of the oxygen
out of the plasma.
Actually, they sop about
98.5% of the oxygen.
So these red blood cells are
just traveling and they're
going to go back to the heart.
They are what make
our blood red.
So you have this thing,
hemoglobin, that's sitting in
red blood cells.
It's sopping up all
the oxygen.
So it keeps the oxygen
concentration and the actual
plasma low.
You have nothing like
that for nitrogen.
There is no cell that's sopping
up the nitrogen.
Nitrogen does not bond
to hemoglobin.
So that's why oxygen
is taken up so
much better than nitrogen.
It's a very interesting question
because if you just
think about how much nitrogen
is, it's kind of a very
natural idea.
Now I want to focus a little
bit on the red blood cell
itself because it's
fascinating.
In the video on the structure
of the cell, I start off
saying, all cells have
a membrane and
they all have DNA.
Now, the fascinating thing about
a red blood cell-- I
already said it has millions
of hemoglobin molecules or
proteins inside of it.
The fascinating thing
about a red blood
cell-- it has no nucleus.
And no DNA.
This is mind boggling when
I first found out.
I was like, well, why
is it a cell?
Is it really even
a living thing?
And it turns out when
it's growing,
it does have a nucleus.
All cells need a nucleus with
DNA in order to generate the
proteins that build it up,
in order to exist and
structurally make itself the way
it needs to be made, but
the whole point of a red blood
cell is to contain as much
hemoglobin as possible.
And so you can imagine, this
is actually a favorable
evolutionary trait, that as red
blood cells are ready to
go into business, you've built
the whole structure, they
actually get rid of
their nucleus.
They actually push their nucleus
out of the cell and
the whole reason why that's
beneficial is, that's more
space for hemoglobin.
Because the more hemoglobin you
have, the more oxygen you
can take up.
And I can do a ton of videos
on hemoglobin and all of
that-- and actually, I'm going
to do a lot more on the
circulatory system so don't
worry about that, but I want
to go over one other really
interesting thing about
hemoglobin.
We already talked about
red blood cells.
I think it's fascinating that
they actually don't have a
nucleus in their mature form.
They actually have
very short lives.
They live maybe 80, 120 days
so they're not these long
lived cells-- so it's almost
a philosophical question.
Are are they still alive once
they've lost their DNA or are
they just vessels for oxygen
that aren't really alive
because they aren't regenerating
and producing
their own DNA?
So actually, instead of going
into the hemoglobin discussion
right now, I'll leave you
there in this video.
I realize I've been making
20-minute videos where my goal
is really to make
ten-minute ones.
So I'll leave you here and in
the next video, we'll talk
more about hemoglobin and
the circulatory system.
About this Video
Apr 18, 2026 Last updated
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