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. As always, please support our channel! Like, subscribe, ring the bell so you
know when our next videos are coming! And until next time, be careful
with those heartstrings. Only allow certain people
to tug on those things...