Human biology
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The Lungs and Pulmonary System
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Red blood cells
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Circulatory System and the Heart
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Hemoglobin
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Anatomy of a Neuron
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Sodium Potassium Pump
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Correction to Sodium and Potassium Pump Video
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Electrotonic and Action Potentials
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Saltatory Conduction in Neurons
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Neuronal Synapses (Chemical)
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Myosin and Actin
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Tropomyosin and troponin and their role in regulating muscle contraction
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Role of the Sarcoplasmic Reticulum in Muscle Cells
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Anatomy of a muscle cell
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The Kidney and Nephron
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Secondary Active Transport in the Nephron
Circulatory System and the Heart Introduction to the circulatory system and the heart
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- Where I left off in the last video, we talked about how the
- hemoglobin in red blood cells is what sops up all of the
- oxygen so that it increases the diffusion gradient-- or it
- increases the incentive, we could say, for the oxygen to
- go across the membrane.
- We know that the oxygen molecules don't know that
- there's less oxygen here, but if you watch the video on
- diffusion you know how that process happens.
- If there's less concentration here than there, the oxygen
- will diffuse across the membrane and there's less
- inside the plasma because the hemoglobin is sucking it all
- up like a sponge.
- Now, one interesting question is, why does the hemoglobin
- even have to reside within the red blood cells?
- Why aren't hemoglobin proteins just freely floating in the
- blood plasma?
- That seems more efficient.
- You don't have to have things crossing through, in and out
- of, these red blood cell membranes.
- You wouldn't have to make red blood cells.
- What's the use of having these containers of hemoglobin?
- It's actually a very interesting idea.
- If you had all of the hemoglobin sitting in your
- blood plasma, it would actually hurt
- the flow of the blood.
- The blood would become more viscous or more thick.
- I don't want to say like syrup, but it would become
- thicker than blood is right now-- and by packaging the
- hemoglobin inside these containers, inside the red
- blood cells, what it allows the blood to do
- is flow a lot better.
- Imagine if you wanted to put syrup in water.
- If you just put syrup straight into water,
- what's going to happen?
- The water's going to become a little syrupy, a little bit
- more viscous and not flow as well.
- So what's the solution if you wanted to
- transport syrup in water?
- Well, you could put the syrup inside little containers or
- inside little beads and then let the beads flow in the
- water and then the water wouldn't be all gooey-- and
- that's exactly what's happening inside of our blood.
- Instead of having the hemoglobin sit in the plasma
- and make it gooey, it sits inside these beads that we
- call red blood cells that allows the flow to still be
- non-viscous.
- So I've been all zoomed in here on the alveolus and these
- capillaries, these pulmonary capillaries-- let's zoom out a
- little bit-- or zoom out a lot-- just to understand, how
- is the blood flowing?
- And get a better understanding of pulmonary arteries and
- veins relative to the other arteries and veins
- that are in the body.
- So here-- I copied this from Wikipedia, this diagram of the
- human circulatory system-- and here in the back
- you can see the lungs.
- Let me do it in a nice dark color.
- So we have our lungs here.
- You can see the heart is sitting right in the middle.
- And what we learned in the last few videos is that we
- have our little alveoli and our lungs.
- Remember, we get to them from our bronchioles, which are
- branching off of the bronchi, which branch off of the
- trachea, which connects to our larynx, which connects to our
- pharynx, which connects to our mouth and nose.
- But anyway, we have our little alveoli right there and then
- we have the capillaries.
- So when we go away from the heart-- and we're going to
- delve a little bit into the heart in this video as well--
- so when blood travels away from the heart, it's
- de-oxygenated.
- It's this blue color.
- So this right here is blood.
- This right here is blood traveling away from the heart.
- It's going behind these two tubes right there.
- So this is the blood going away from the heart.
- So this blue that I've been highlighting just now, these
- are the pulmonary arteries and then they keep splitting into
- arterials and all of that and eventually we're in
- capillaries-- super, super small tubes.
- They run right past the alveoli and then they become
- oxygenated and now we're going back to the heart.
- So we're talking about pulmonary veins.
- So we go back to the heart.
- So these capillaries-- in the capillaries we get oxygen.
- Now we're going to go back to the heart.
- Hope you can see what I'm doing.
- And we're going to enter the heart on this side.
- You actually can't even see where we're
- entering the heart.
- We're going to enter the heart right over here-- and I'm
- going to go into more detail on that.
- Now we have oxygenated blood.
- It's red.
- And then that gets pumped out to the rest of the body.
- Now this is the interesting thing.
- When we're talking about pulmonary arteries and veins--
- remember, the pulmonary artery was blue.
- As we go away from the heart, we have de-oxygenated blood,
- but it's still an artery.
- Then as we go towards the heart from the lungs, we have
- a vein, but it's oxygenated.
- So that's this little loop here that we start and I'm
- going to keep going over the circulation pattern because
- the heart can get a little confusing, especially because
- of its three-dimensional nature.
- But what we have is, the heart pumps de-oxygenated blood from
- the right ventricle.
- You're saying, hey, why is it the right ventricle?
- That looks like the left side of the drawing, but it's this
- dude's right-hand side, right?
- This is this guy's right hand.
- And this is this dude's left hand.
- He's looking at us, right?
- We don't care about our right or left.
- We care about this guy's right and left.
- And he's looking at us.
- He's got some eyeballs and he's looking at us.
- So this is his right ventricle.
- Actually, let me just start off with the whole cycle.
- So we have de-oxygenated blood coming from the rest of the
- body, right?
- The name for this big pipe is called the inferior vena
- cava-- inferior because it's coming up below.
- Actually, you have blood coming up from the arms and
- the head up here.
- They're both meeting right here, in the right atrium.
- Let me label that.
- I'm going to do a big diagram of the heart in a second.
- And why are they de-oxygenated?
- Because this is blood returning from our legs if
- we're running, or returning from our brain, that had to
- use respiration-- or maybe we're working out and it's
- returning from our biceps, but it's de-oxygenated blood.
- It shows up right here in the right atrium.
- It's on our left, but this guy's right-hand side.
- From the right atrium, it gets pumped
- into the right ventricle.
- It actually passively flows into the right ventricle.
- The ventricles do all the pumping, then the ventricle
- contracts and pumps this blood right here-- and you don't see
- it, but it's going behind this part right here.
- It goes from here through this pipe.
- So you don't see it.
- I'm going to do a detailed diagram in a second-- into the
- pulmonary artery.
- We're going away from the heart.
- This was a vein, right?
- This is a vein going to the heart.
- This is a vein, inferior vena cava vein.
- This is superior vena cava.
- These are veins.
- They're de-oxygenated.
- Then I'm pumping this de-oxygenated blood away from
- the heart to the lungs.
- Now this de-oxygenated blood, this is in an artery, right?
- This is in the pulmonary artery.
- It gets oxygenated and now it's a pulmonary vein.
- And once it's oxygenated, it shows up here in the left--
- let me do a better color than that-- it shows up right here
- in the left atrium.
- Atrium, you can imagine-- it's kind of a room with a skylight
- or that's open to the outside and in both of these cases,
- things are entering from above-- not sunlight, but
- blood is entering from above.
- On the right atrium, the blood is entering from above.
- And in the left atrium, the blood is entering-- and
- remember, the left atrium is on the right-hand side from
- our point of view-- on the left atrium, the blood is
- entering from above from the lungs, from
- the pulmonary veins.
- Veins go to the heart.
- Then it goes into-- and I'll go into more detail-- into the
- left ventricle and then the left ventricle pumps that
- oxygenated blood to the rest of the body via the
- non-pulmonary arteries.
- So everything pumps out.
- Let me make it a nice dark, non-blue color.
- So it pumps it out through there.
- You don't see it right here, the way it's drawn.
- It's a little bit of a strange drawing.
- It's hard to visualize, but I'll show it in more detail
- and then it goes to the rest of the body.
- Let me show you that detail right now.
- So we said, we have de-oxygenated blood.
- Let's label it right here.
- This is the superior vena cava.
- This is a vein from the upper part of our body from
- our arms and heads.
- This is the inferior vena vaca.
- This is veins from our abdomen and from our legs and the rest
- of our body.
- So it it first enters the right atrium.
- Remember, we call the right atrium because this is
- someone's heart facing us, even though this is on the
- left-hand side.
- It enters through here.
- It's de-oxygenated blood.
- It's coming from veins.
- the body used the oxygen.
- Then it shows up in the right ventricle, right?
- These are valves in our heart.
- And it passively, once the right ventricle pumps and then
- releases, it has a vacuum and it pulls more blood from the
- right atrium.
- It pumps again and then it pushes it through here.
- Now this blood right here-- remember, this one still is
- de-oxygenated blood.
- De-oxygenated blood goes to the lungs to become
- oxygenated.
- So this right here is the pulmonary-- I'm using the word
- pulmonary because it's going to or from the lungs.
- It's dealing with the lungs.
- And it's going away from the heart.
- It's the pulmonary artery and it is de-oxygenated.
- Then it goes to the heart, rubs up against some alveoli
- and then gets oxygenated and then it comes right back.
- Now this right here, we're going to the heart.
- So that's a vein.
- It's in the loop with the lungs so it's a pulmonary vein
- and it rubbed up against the alveoli and got the oxygen
- diffused into it so it is oxygenated.
- And then it flows into your left atrium.
- Now, the left atrium, once again, from our point of view,
- is on the right-hand side, but from the dude looking at it,
- it's his left-hand side.
- So it goes into the left atrium.
- Now in the left ventricle, after it's done pumping, it
- expands and that oxygenated blood flows
- into the left ventricle.
- Then the left ventricle-- the ventricles are what do all the
- pumping-- it squeezes and then it pumps the
- blood into the aorta.
- This is an artery.
- Why is it an artery?
- Because we're going away from the heart.
- Is it a pulmonary artery?
- No, we're not dealing with the lungs anymore.
- We dealt with the lungs when we went from the right
- ventricle, went to the lungs in a loop,
- back to the left atrium.
- Now we're in the left ventricle.
- We pump into the aorta.
- Now this is to go to the rest of the body.
- This is an artery, a non-pulmonary artery-- and it
- is oxygenated.
- So when we're dealing with non-pulmonary arteries, we're
- oxygenated, but a pulmonary artery has no oxygen.
- It's going away from the heart to get the oxygen.
- Pulmonary vein comes from the lungs to the heart with
- oxygen, but the rest of the veins go to the heart without
- oxygen because they want to go into that loop on the
- pulmonary loop right there.
- So I'll leave you there.
- Hopefully that gives-- actually, let's go back to
- that first diagram.
- I think you have a sense of how the heart is dealing, but
- let's go look at the rest of the body and just
- get a sense of things.
- You can look this up on Wikipedia if you like.
- All of these different branching points have
- different names to them, but you can see right here you
- have kind of a branching off, a little bit below the heart.
- This is actually the celiac trunk.
- Celiac, if I remember correctly, kind of refers to
- an abdomen.
- So this blood that-- your hepatic artery.
- Hepatic deals with the liver.
- Your hepatic artery branches off of this to get blood flow
- to the liver.
- It also gives blood flow to your stomach so it's very
- important in digestion and all that.
- And then let's say this is the hepatic trunk.
- Your liver is sitting like that.
- Hepatic trunk-- it delivers oxygen to the liver.
- The liver is doing respiration.
- It takes up the oxygen and then it
- gives up carbon dioxide.
- So it becomes de-oxygenated and then it flows back in and
- to the inferior vena cava, into the vein.
- I want to make it clear-- it's a loop.
- It's a big loop.
- The blood doesn't just flow out someplace and then come
- back someplace else.
- This is just one big loop.
- And if you want to know at any given point in time, depending
- on your size, there's about five liters of blood.
- And I looked it up-- it takes the average red blood cell to
- go from one point in the circulatory system and go
- through the whole system and come back, 20 seconds.
- That's an average because you can imagine there might be
- some red blood cells that get stuck someplace and take a
- little bit more time and some go through the completely
- perfect route.
- Actually, the 20 seconds might be closer
- to the perfect route.
- I've never timed it myself.
- But it's an interesting thing to look at and to think about
- what's connected to what.
- You have these these arteries up here that they first branch
- off the arteries up here from the aorta into the head and
- the neck and the arm arteries and then later they go down
- and they flow blood to the rest of the body.
- So anyway, this is a pretty interesting idea.
- In the next video, what I want to do is talk about, how does
- the hemoglobin know when to dump the oxygen?
- Or even better, where to dump the oxygen-- because maybe I'm
- running so I need a lot of oxygen in the capillaries
- around my thigh muscles.
- I don't need them necessarily in my hands.
- How does the body optimize where the oxygen is actually
- delivering?
- It's actually fascinating.
Be specific, and indicate a time in the video:
At 5:31, how is the moon large enough to block the sun? Isn't the sun way larger?
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