In today's video, with the help of the cadavers here in the lab, we're going to discuss the
formation of blood clots and see exactly what it is that makes them so incredibly dangerous.
Let's do this.
[Intro]
A blood clot or what's more properly known as a Thrombus actually has three different
components to it.
The first is going to be platelets or thrombocytes.
Now, these are going to be sticky cells that are going to be very integral to the blood
clot structure itself.
You're also going to have red blood cells.
With red blood cells, we're probably all familiar with - these are going to carry oxygen and
carbon dioxide.
You're also going to have a very tough protein called fibrin and we'll go into more detail
of fibrin in just a second.
Now, blood clots can happen for you in a good way or a bad way.
So, the good way is what's called hemostasis.
Hemostasis, you could think of as your body's process, the natural process that's trying
to stop bleeding from occurring.
So, let's say you get cut in the arm, right?
When you cut through the blood vessel and blood starts spraying everywhere, that's obviously
a problem.
So, what happens is those platelets are just flowing, right?
They're naturally circulated in your bloodstream.
Well, they run into that injury and as they run into it, they get stuck the wall and that
actually causes them to become activated and when they become activated, they start secreting
chemicals that will also go into your bloodstream that will alert other cells, like your immune
cells and several other things that first off, we've been injured and second, this is
where the injury is at.
Then, more and more platelets are just running into the ones that are already stuck there
as well as red blood cells and it creates this traffic jam at this location that is
going to help stop the bleeding and we call this the Platelet Plug but this isn't all
of the blood clot because what's also going to be circulating in your bloodstream are
thrombin proteins and they are just waiting for their moments because when they run into
the platelets, they actually go onto the cell membrane and they will then start grabbing
other substances inside of your bloodstream called Fibrinogen and when they grab that
fibrinogen, they convert the fibrinogen into fibrin.
I know that's pretty wordy but just think of it as platelet gets stuck, thrombin goes
to it, thrombin creates fibrin and now you have these tough proteins that start in meshing
themselves in the red blood cells, in the platelets and you get this, which was already
sticky, now really structurally sound blood clot.
We call this the fibrin mesh clot.
All of that is perfectly normal.
You want that to happen because that's how you stop the bleeding.
However, it can happen even if you're not bleeding and this is that bad way that I mentioned.
We call this process Thrombosis.
Thrombosis is basically blood clotting without bleeding.
This can happen in a wide variety of different ways.
Maybe you're smoking.
If you needed another reason to not smoke, there it is.
You can get blood clots.
If this wasn't funny enough, birth control and pregnancy.
So, whether you're trying to prevent the pregnancy from occurring or it happens, either way you're
getting blood clots but another really big contributor is going to be prolonged immobility.
So, this could be something like being confined to a wheelchair or maybe you're on bed rest
or maybe you're just on a really long flight, you know, like 13 plus hours.
What's happening is you're sitting or immobile, you're compressing blood vessels and as you
compress the blood vessel, you're increasing the likelihood that red blood cells and platelets
are going to form that traffic jam and creating a blood clot.
So, if you needed another reason to not just lounge around and get up and move, it helps
prevent blood clots but regardless and those are only a few.
There are many other ways that blood clots can form.
If it has formed though inside of an intact vessel that's not bleeding, well, now things
can actually get pretty scary.
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Alright, let's get back to it.
It's possible for you to find different descriptions and definitions of thrombi in the various
medical text and literature.
It really just depends on who's teaching it and for me, I've always taught that there
are two primary forms of thrombi.
You have what's called a Mural Thrombus and then an Occlusive Thrombus.
So, I want us to take a look at this heart here to understand a mural thrombus.
So, you're looking at an anterior view of the heart.
You can see blood vessels up here like this massive one called the aorta and you can also
see like pulmonary trunk here and then we've also made an incision into the heart wall
that we can open up and you can see inside of the heart itself.
Now, a mural thrombus, Mural just means wall, like a mural painting.
So, in this case, the blood clot would be forming, say if we open up this aorta here,
inside the blood vessel on the wall, right?
So, blood flow is still traveling past it but the blood clot has formed.
That could happen in the aorta although typically happens in the descending aorta but that doesn't
really matter right now or it could happen inside of the chambers of the heart.
So, let's say it were to form right here where my finger is.
You can see there's a lot of space in the chamber.
That means it could potentially create a very massive mural thrombus.
Now, an occlusive thrombus, Occlusive just means obstruction, right?
It's blocking blood flow.
So, what can happen is that it naturally forms that way.
Let's say you're sitting for a prolonged period of time and as you're blocking off the blood
vessel, you naturally create an occlusive blood clot, right?
That can happen but another option if we go back to the heart here is let's say the mural
thrombus that was growing here in the left ventricle detache, and as the heart contracts
and pushes it, it's now travelling through the aorta and travelling through many different
blood vessels that are branching off of the aorta and at that point, once it gets to a
small enough blood vessel that it can't fit, it now becomes an occlusive thrombus.
So, it's possible for mural thrombi to become occlusive thrombi but it's also possible that
the mural thrombus stays that way, never dislodges and it's also possible that the blood clot
grows to be occlusive right off the bat.
Now, when that blood clot has dislodged and is now travelling through your bloodstream,
we give it a new name.
It's now defined as an Embolus but blood clots aren't the only form of emboli.
In fact, anything that's travelling inside of your bloodstream that has the potential
to cause a blockage at some point down stream, that's a embolis.
So, it could be fat that's traveling in your blood.
It could be amniotic fluid.
It could even be air.
All of those have the potential to cause what's called an embolism, right?
So, the embolis is the thing travelling, an embolism is the area has suffered an embolism
if the blood flow has been restricted in that area.
The main types that I want to focus on for our video are going to be known as Venous
Thrombo Embolism and Arterial Thrombo Embolism.
Basically, that's just saying a blood clot that caused an embolism in your venous system
or your arterial system.
However, there also can be micro clots.
These are clots that form in capillaries, which are blood vessels that are so small
that red blood cells sometimes have to go through single files.
So, those are really really small clots but to best understand this, I want to start off
by discussing what's called a deep vein thrombosis.
You are now looking at a cross section of the mid thigh.
So, as I kind of move the leg like this you can see exactly what we're looking at.
Now there's a lot to look at here.
So I want to quickly orient you - this is the femur and that makes this the anterior
side of the thighs.
So, you're looking at the quadriceps which makes this the posterior and medial aspect
but we want to focus our attention here to these blood vessels.
So, this thicker one right here that I'm pointing to, that's the femoral artery and then right
next to it - let's see if I can get my probe in there.
It's a little difficult for me to do - that's going the femoral vein right next to it and
over here you're also going to see the deep femoral artery and deep femoral vein.
So, we're talking about deep vein thrombosis.
This is going to occur surprise surprise in the deeper veins.
I mean, if you look at this, there are going to be superficial veins all over the place
but it's these deep veins that we're really concerned with especially when it gets into
the lower leg here.
But this can happen in the arms but it's almost always going to happen in the pelvis and in
the legs.
Now, what you can experience with the deep vein thrombosis is going to be pain, tenderness
because there's swelling.
It's going to be red and that pain can actually increase when you're putting more weight on
it and so people tend to not want to stand up or move much when they have this.
But you're also going to get often times what's called pitting edema and that's where there's
so much swelling that when you poke it, it actually creates a pit.
Again, surprise surprise.
Now, the risk here is that this will actually embolize and if it detaches and embolizes,
it's then going to travel up the cardiovascular system because if you remember, veins take
blood back to the heart.
So, now that it's inside of the venous system and it's embolized, that means it's headed
towards the heart and that sets it up to create something very problematic which we call a
Pulmonary Embolism.
A pulmonary embolism happens when there is a sudden blockage or occlusion of a pulmonary
artery.
Now, just remember, the DVT, right?
It's dislodge, it's now embolized and now you have this embolis travelling through your
venous system on its way back to the heart.
And as it goes back to the heart, which again, we have right here, this is going to be the
anterior view the heart, this is going to be the right ventricle.
What will happen is it will make its way into this right ventricle and I know it doesn't
really look like much, but we've cut this little window to allow you to see in there.
Once it gets into the right ventricle, right ventricle contracts and attempts to send it
the lungs.
This is going to be a right lung.
Now, if we look at it from this medial side, you can see where the bronchial tubes, right?
The respiratory tract is branching but if you look closely, you should also be able
to see a bunch of little blood vessels on either side, right?
You're going to see pulmonary arteries and pulmonary veins.
Arteries take blood away from the heart.
Meaning that the blood is going to the lungs.
Veins bring blood back to the heart.
So, we now have oxygenated blood heading back to the heart.
Well, if this - depending on size of the embolis, it could cause a pretty massive blockage or
maybe it's a more minimal blockage because I want you to understand, these vessels will
just get smaller and smaller and smaller as they permeate the lung tissue but that can
also mean if you have a blockage that the lungs themselves are starting to get deprived
of blood.
So, you can start to accumulate lung damage.
This also means that the lungs aren't able to oxygenate the blood as efficiently.
So, typically, someone with a pulmonary embolism will experience chest pain and shortness of
breath.
Just makes per sense but you also have to think that the heart is going to have to start
working harder because if there's a blockage, the heart - the blood comes back to the heart,
right?
It's not able to do it.
It's going to be like, "oh well, I'm going to just work harder here" and it starts to
increase its rate and its strength of contraction in a desperate attempt to get the blood there.
That can result in cardiac arrest, stress, and strain on the heart, can cause heart failure.
In severe cases of pulmonary embolism, sure, you can die from cardiac arrest and that's
obviously a pretty massive problem but depending on the size of this - the duration of it because
sometimes these pulmonary embolisms can be dragged on for weeks to months of treatments.
When you're getting treated with anticoagulants that are attempting to just slowly break that
clot down and so then it's non problematic but if it's massive enough, someone could
possibly die within hours or possibly even minutes.
It really depends.
Pulmonary embolisms are very, very scary.
Now, That's if it's a - if it's a vein, right?
But if we have a clot in an artery, it is now possible for it to head to the brain.
Now, we're going to do an entire video on strokes.
So, I'm probably going to be relatively brief here because there is a ton to go in with
strokes but I want to be very clear about something from the start and that is that
blood clots like we've been talking aren't the main or primary cause of most strokes.
Instead, that's typically going to be fatty deposit that are going to be in things like
arteries.
So, think like atherosclerosis or arteriosclerosis.
So, maybe from poor diet or genetic factors and those fatty deposits because if you remember,
anything that's traveling in the bloodstream can be an embolis.
So, that's going to be the main or primary cause.
However, it's still is definitely possible if you have a - say a mural thrombus that
forms inside of the heart or maybe inside of the beginnings of the aorta before it starts
splitting and going to other parts of the body.
So, what I want you to picture is that there is this mural thrombus that exits the heart
and then go straight up towards the neck and to the brain.
Now, what you have in front of you here is going to be the two cerebral hemispheres of
the brain.
Now, if you'll notice, there are some incisions here.
This was removed by a student of ours during a dissection course.
So, all in all, though I think she did a really good job but what I want you to focus on are
going to be all of these blood vessels here on the surface of the brain.
Now, these are meningial blood vessels and again, I want to be very clear.
These are not typically the blood vessels that are affected during a stroke.
However, they give you a really good visual of just how vascular the brain is and what
I want you to think about is just how much more vascularization is on the inside of the
brain and what is typically going to happen as I rotate and you can see that posterior
side so you're now looking at the back of the brain, the occipital lobes.
So, what's going to happen is the aorta which comes off of the heart is going to branch
into the carotid arteries and then the carotid arteries are going to branch into the cerebral
arteries and this is gonna branch and branch and branch.
Well, what can happen is let's say you had a mural thrombus that dislodges and it goes
straight up the carotids, depending on how massive it is, it could block one of the carotids
like the internal carotid artery or maybe it blocks the one of the cerebral arteries
and that would cause a stroke.
A stroke is simply going to be lack of blood, lack of oxygen going to the brain tissue itself.
Now, if it's a smaller thrombus, it could make it farther away from that and who knows?
Maybe it actually could get into the meningial system.
All things are definitely possible.
It's more so about what's going to be probable but like I said, strokes, we're going to do
an entire video on them because there is so much more to cover but at least you now understand
that a blood clot could potentially result in one.
Now, when it comes to treating just pretty much all blood clots, the standard care is
going to be anticoagulants and I also want to be very clear because I think I might have
misrepresented or misspoke earlier when I discussed anticoagulants.
When you have a pulmonary embolism, yes, you treat with anticoagulants but I want you to
know, anticoagulants don't necessarily break down a pre-existing blood clot.
Instead, anticoagulants are what most people would refer to as a blood thinner are there
to prevent more blood clots from forming.
Instead, if say like with a pulmonary embolism, if you were to try and break it down itself,
there are medications and enzymes that are designed for that that don't technically classify
as an anticoagulant but still, if you suffer from DVT or you have in the past, what they
will typically give you is anticoagulants.
However, depending on where your blood clot is, they could go in surgically.
They can enter in through blood vessels and actually break the blood clot apart it can
actually take it out.
It really depends on where it is.
However, surgically trying to remove one from the lung is not - that's not something they
do these days.
They used to do that but now they've shifted away from that.
However, it's fairly common to go for it if it's in your arms or your legs because it's
just going to be far less damaging to the surrounding area but treatment, again, typically
is going to be anticoagulants but they do have several other methods that they can pursue.
Thanks for watching everybody.
I really hope you enjoyed today's video.
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