And you are in luck because we are about to go on a "Magic School Bus" journey where we
go into the heart, and see those valves as if we're flowing through with blood.
And where we want to start is in this structure, called the right atrium...
Welcome to the anatomy lab everyone!
Today we're going to talk about your heart strings.
Yes — you do have these little strings inside your heart.
Although you may have someone metaphorically tugging on those strings this coming Valentine's
Day, we need to figure out what's literally tugging on these inside your heart, and
what happens if they snap or even break — which is kind of the same thing...
I'm Jonathan with the Institute of Human Anatomy, and we're going to use
these very clean and non-goopy hearts, to learn about your heartstrings.
So... let's do this!
First some basic ideas about the heart.
Most of you have felt it's in the center of the chest or close to the center of the chest.
Specifically we'll use Geoffrey and say posterior to this bone that we call the sternum.
Two-thirds of the mass of the heart is slightly left to the midline or the sternum.
Now, Geoffrey is super cool, and cool to learn anatomy from, but you want to see it on the actual
real deal — or the cadaver here — so let's do that, but maybe put gloves on first — this time...
So what you're seeing here is the thoracic cavity.
You can see the diaphragm here, just this dome-shaped muscle.
Then up here you're seeing the cut edge of the sternum.
Obviously you can see the lungs on either side — those will be for a future video...
Then you see the heart in the center of the chest,
again, more biased over here on the left side, but sitting in a sac.
The sac has a name though.
The sac that you can see this tissue here is called the pericardial sac.
It's kind of like we've cut it so it's like a little bit of a
Valentine's present that you could open up and see what's inside, so... are you ready?
Let's do this!
[Jonathan makes a strange attempt at an epic sound...]
That was a shameless sound effect...
But anyway...
You can see the heart truly sitting in the sac — it's so awesome!
You can see a couple of things that I want to point out here.
All this yellowy tissue here is referred to as the epicardium.
It's primarily made up of what we call epicardial fat.
This can vary in thickness based upon a person's body habitus — or composition if you will.
You can see the cool aorta here...
I mean, that's got some recoil to it...
Biggest artery in the human body!
This gives us the basic idea of where it is — just some outside or external structures, but the
valves are inside, so we need to get a dissection where we can see the inside of the heart.
So, to the heart dissections!
We know that the heart is a pump,
and it's extremely important for this heart — or this organ — that when it does pump blood,
it does it efficiently in one direction, or what we say unilateral blood flow.
It's really important that that blood doesn't flow back where it originally came from.
In order for the heart to accomplish this the heart has four valves to stop
this back-flow of blood, and two of those valves have the heart strings on them.
You are in luck, because we are about to go on a "Magic School Bus" journey where
we go into the heart and see those valves as if we're flowing through with blood.
And where we want to start, is in this structure called the right atrium.
So if you take a look, I've got two hearts here — I just want to orient you.
We're going to use either one based upon which anatomy we're going to talk about
because they're slightly dissected differently.
You can see this one's a little more yellowish and
that's just because it still has some of the epicardial fat on it,
where this one we've removed all the epicardial fat that was originally on the heart.
So like I said, let's take a look at this right atrium.
So some quick details on this right atrium before we dive in.
This is receiving deoxygenated blood — and I'm opening up the
chamber here — from the entire body.
Essentially this blood is deoxygenated because it's got a lot of carbon dioxide,
other metabolic waste products.
The whole job of this right side of the heart is to get that blood to the lungs
so we can get rid of the carbon dioxide and bring in new oxygen.
You can see this hollow chamber, but also some really cool muscle here that we call
the pectinate muscle — these these are little muscle fibers for a little bit of contraction.
It's receiving this blood.
And now... zoom into the "Magic School Bus"!
So you can see we have entered this right atrium.
There's that pectinate muscle on the right, and you can see this valve
called the tricuspid valve, because it's got three cusps that we're about to pass through.
And here we go...
You can see there's this cool muscle called trabeculae carneae,
which means little beams of meat — essentially — that you're seeing there.
And then we turn upside down to look at the valves and... freeze there!
Can you see those white strings?
Those are the heart strings, and those are called the chordae tendineae.
Let's zoom out and take a look at where we are.
So that was super awesome, but I want you guys to take a look at these hearts here,
specifically this one over here.
Where we left off in our little "Magic School Bus",
we were all "sitting down" right here, looking up at two valves.
The valve we came through was the tricuspid valve, and look how freaking awesome this is!
These — if I can hook them properly — are your heart strings, that I mentioned
are called the chordae tendineae, or sometimes pronounced tendin-e-eye...
But those are the heart strings attaching to the cusps
right there, and again there'd be three of these cusps because it's the tricuspid valve.
In the beginning we posed this question, "what is tugging on your heart strings?"
Well take a look at this right here...
This is called the papillary muscle.
Papillary means "nipple-like projection".
So in other words... "what's tugging on your heart string?"
A nipple-like projection, which is this muscle that can contract here...
Just real quick since we're here, I want to mention — I mentioned those
little beams of meat there... those were called the trabeculae carneae.
Those are pretty awesome because they help the ventricle contract.
Now take a step back before we go back into the "Magic School Bus".
We talk about these valves being like one-way saloon doors.
For those of you who love the saloon doors of the
old west — those are fun because they flop back and forth either direction.
Think of these as modified...
We've got those strings or those chordae tendineae coming on either
little flap here — and I only have two because I don't have three hands for this tricuspid
valve — and when we enter in from the right atrium to the right ventricle, that just puts
slack on those chords, no big deal and they just passively allow the blood to come in.
But when things start to contract and the doors start to swing back the other way... because of
those cords and that papillary muscle, it stops it from pulling back, like so.
Because those chords have tension on them or the heart strings.
If we need that papillary muscle to contract, it pulls and puts tension on so it won't flap
back the other direction, and allow blood to go back in the wrong chamber.
We need it to go out the other valve where, we left off in the "Magic School Bus."
So let's jump right back to where we were, if you remember,
we were down in this sequence — or this area — of the heart looking up.
So you can see as one valve is closed the other one's open and vice versa.
You can see we're about to move up to this really cool little valve, called the pulmonary valve.
We're about to go through this pulmonary valve — it's named after the lungs,
and that's what pulmonary refers to — and poof!
We enter into the pulmonary trunk, and again, zoom back out!
So if you take a look
at this heart, we went up and instead of going back where we came from we exited out a different
valve and went out this structure called the pulmonary trunk that you can see right here.
It's a tube, like so.
I'm going to show you another dissection on the other heart, but
this is going to take blood to the right lung and the left lung,
so we can get rid of the carbon dioxide and get more oxygen coming in.
This is, again, just the same view of the heart, just a smaller heart.
The pulmonary trunks opened up, and you can see the pulmonary valve that I mentioned.
These ones are a lot more simplistic — or this valve — and it doesn't actually have
heart strings, and it just needs to let blood passively pass out.
If any blood tries to come back in, you can see these little cups
will actually catch the blood before it would go back into the right ventricle.
So of course we're going to finish our journey through the heart on the "Magic School Bus".
Remember we left off by taking blood to the lungs — it was deoxygenated
blood — to get rid of the carbon dioxide, bring in more oxygen,
it diffuses into the blood, and now we bring that back to the left side of the heart.
A couple of things I want to mention before we go back on "the bus"...
One is, remember I mentioned there's two of the four valves that have the heart strings on it.
We're gonna see the second valve on the left side.
Also, I asked earlier "what happens if the heart strings break or snap?"
Well often that damage occurs on the left side,
in this valve that we call the mitral valve, also known as the bicuspid valve.
So let's keep that in mind as we go through this journey.
Let's just orient ourselves back to this heart here.
Here is the back side of the heart.
That was the right atrium, here.
I'm going to turn it over to the left here, and this is
the opening into the left atrium of the heart.
So... let's enter "the bus"!
As you can see we've entered in.
You can see the pectinate muscle on the left, but look at that valve — only two cusps!
We're heading through that valve... you can see those little beams of muscle, again called the
trabeculae carneae — and we're gonna get in and probably turn around and look up again.
There we have it.
Let's freeze the frame here!
So you can see there's the valve — only two cusps.
You can see the heart strings there, and the other valve on the left that we need to exit.
Okay! So... let's orient ourselves on the actual heart again.
Instead of being in the right ventricle we're now in the left ventricle,
but we're in the same kind of lower region of the ventricle looking up at those two valves.
You can see right here we've got the chordae tendineae, or what we call the
heart strings — and here, but the poor little papillary muscles pulled away from the wall.
So speaking of damage — that's the papillary muscle being damaged, which can happen.
But let's talk about what happens if the chord snaps or ruptures.
That's a big deal!
Think about our saloon door analogy.
Remember, opening up no problem because we got slack in the cords but when we closed the door
those cords stopped it from flapping back the other direction.
So imagine [weird Jonathan noise] — because great
sound effects for snapping cord — [another weird Jonathan noise]
door opens, blood's now able to flow back where it originally came from,
which we don't want to occur.
When a valve flops back the other direction that it's not supposed to in the case that I
just mentioned there, that's called prolapse, or in this case bicuspid valve prolapse or mitral
valve prolapse, because that left sided valve is called the bicuspid or the mitral valve.
Now that increases the load or the work that the heart has to do because it already pumps the blood
into that chamber and now it's re-pumping it back into the chamber,
which is no fun for the poor little heart.
Let's finish the journey and leave the left side of the heart and go to the whole body.
So here we go!
You can again see the valves open and close separately.
Because that's a functioning mitral or bicuspid valve,
we're going to go out the right direction through this valve called the aortic valve — because
crazy... it's in the aorta — and then we go down the aortic arch like a roller coaster ride....
[yet another strange Jonathan noise...] Yes!
If you couldn't tell by that, I have this fantasy of creating
an amusement park of the inside of the human body.
I mean, could you imagine like going over the aortic arch
and then... [yet another... strange Jonathan noise....]
like on a roller coaster?
We'd be at an amusement park AND be learning anatomy!
It would be like, awesome!
Disneyland for bodies!
Anyway, back to the deed at hand here — some things that can cause
damage to the chordae tendineae —or your heartstrings — are things like infections,
like endocarditis or rheumatic heart disease.
Also things like connective tissue disorders that affect collagen production, because those little
heart strings use collagen to create their tensile strength when they're pulling on those cusps.
So hopefully that doesn't happen because we really love just metaphorically tugging on
our heartstrings, and just the papillary muscle or those nipple-like projections
tugging on them, appropriately.
Thanks for watching everyone!
Hopefully we learned some new information on the heart with our "Magic School Bus" journey.
And, if you liked the "Magic School Bus" journey, you might have noticed that cool software we used.
That was brought to you by ShareCare YOU.
They're an affiliate of ours, so we'll put the link below.
These guys have an awesome software platform for students, for teachers,
for anyone who wants to learn about the human body.
You can go on tours of organs... the digestive system, more on the heart,
reproductive anatomy... you name it!
They've got so many things for you to do, and different types of platforms.
If you're a student, they have one option.
If you're more of an educator and you want to do presentations, they've got another option.
They're offering some discounts, so go ahead and take a look at the link below.
Like I said we'll put that in the description.
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And until next time, be careful with those heartstrings.
Only allow certain people to tug on those things...