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Structure and function of the heart.

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the heart is part of our circulatory system

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which is one of the three main systems responsible for our
cellular respiration.

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Those three systems are; the circulatory system, respiratory and digestive.

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So with cellular respiration, we need oxygen and glucose
which then gives energy and carbon dioxide and water as our waste product.

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So the circulatory respiration is responsible for providing oxygen to our cells
and then removing that waste product of carbon dioxide.

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So looking at the diagram of the heart, we can see that it is split up
into four major sections internally

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and then we've got these four vessels aswell.

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So it is a case of identifying which of these vessels we are looking at.

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With the heart then, adove the heart we have our lungs 
and below we have representing the body's cells. 

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So we breathe in oxygen to the lungs so we have oxygenated blood
coming down to the heart.

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This is known as the pulmonary system.

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Between the heart and the rest of the body's cells
is known as the systemic system.

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Internally to the heart then, we've got these 4 chambers

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The upper chambers known as the atrium
and the lower chambers, the ventricles.

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You will also notice when you look that with the muscle mass
that it actually changes.

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So on the left hand side we have a larger muscle mass
so we have the left atrium and the left ventricle.

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And then with less muscle mass, we've got the right atrium
and the right ventricle.

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So of these four vessels we have veins and arteries.

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So a good way of remembering, vein -when you spell 'vein'
I-N 'in'

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veins bring blood into the heart.

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With arteries, beginning with 'A' it brings blood away from the heart.
Or as I like to say, we go out of the heart.

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So when we've got this lovely oxygenated blood
coming down from the lungs into the heart, this is our pulmonary vein.

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Blood goes through the atrium, down to the ventricle and then
out our heart through the artery

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in the largest artery so it is also known as the 'Aorta'

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Bringing that oxygenated blood to the rest of your body's cells
as part of cellular respiration.

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So carbon dioxide is a waste product, de-oxygenated blood now
coming away from the body's cells back to the heart.


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So we are going in the heart, so we have another vein
but this time this our largest vein so it is known as the 'Venacava'

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Through the atrium, down the ventricle and back out our heart.
But this time we are coming up to the lungs so it is known as the 'Pulmonary Artery'

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Deoxygenated blood into the lungs so we breathe out the carbon dioxide

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So when we look at the heart and it's external structure
you can see this lovely, really thick cardiac muscle.

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And when we look at the top of the heart we can also see the four vessels.

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One, two, three and four.

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So we are now going to perform the heart dissection so we can see these chambers inside,

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the route of bloodflow and then correctly identify each of these vessels.

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So in order to perform the heart dissection, the best way to start 
is that we need to find that central point that separates the left and right hand side.

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And this is a section that we call the septum.

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So feeling around the heart you should be able to feel those
hollowed chambers the atrium and ventricle.

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And then that lovely, muscular septum right down the centre of the heart.

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And what I'd like us to do, using the surgical scissors is going in through
one of the vessels, we are going to cut down the outer of the septum.

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Always checking yourself that you are not cutting through the septum
and that we are staying within those chambers.

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You really get to start to see just how thick this cardiac muscle is.

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It is the only muscle in your body that never stops contracting.
Obviously until the day that you die.

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So we can see then that we've got the septum, 
the wall of the heart and we have opened up into those chambers.

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These tendons then are what also contribute to the contraction of opening and closing 
between the atrium and the ventricle for the bloodflow.

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So I want to do the same again but this time down the other side of the septum
so we're kind of opening the heart up like a book.

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And you'll see with the way I am cutting it can be really quite tough.
Which you'd imagine it has to be.  

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Again just checking yourself, that you are not going into the septum.

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And once again, we've got it nice and open now.

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Ventricle, atrium

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ventricle and atrium, and you can really see the structural difference
between each of the chambers aswell.

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FInding a blood clot is also not uncommon when it comes to dissection,
so you just move that out of the way.

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Hopefully you can see then as I mentioned at the beginning, the cardiac wall,
the difference in its thickness.

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So we can really see one side is incredibly thicker than the other.
So we know now, this is our left hand side and the right hand side.

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So, left atrium, left ventricle, the right atrium and the right ventricle.

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And again, we can see the tendons in either side.

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So in order to identify our vessels, so what I want to do first then,
is I am going to turn the heart around.

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So that it is facing us the right way up

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and we are going to imagine now, the bloodflow from the lungs to the heart 
and then from the heart to the rest of your body's cells.

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Left hand side oxygenated blood, you breathe oxygen in through the lungs
oxygenated blood coming from the lungs to the heart.

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Through into the atrium. So if it is from the heart into the atrium,

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This vessel here that I have cut into has to be the pulmonary vein.

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We are going in the heart

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Down the ventricle and then we go out of the ventricle

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Just getting through the tendons. You know what I am just going to cut those.

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So then down the ventricle, out through and we can see then, we are coming away from the heart.

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So this must be the arorta, the largest artery in your body.

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So all this oxygenated blood is being fed to your body's cells.

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They use that for cellular respiration, so the waste product of carbon dioxide
comes back to the heart, 

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in the heart through the atrium. So this vessel that I cut through here must be a vein,
the largest vein, so this is the venacava,

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down the ventricle and then coming out

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finding the root, there we go. 
Out of the ventricle, out of this vessel here, 

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bringing that deoxygenated blood back to the heart,
so this has to be the pulmonary artery.

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To summarise, the heart then is part of our circulatory system
which provides us with the oxygen to our body's cells for cellular respiration.

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As a by product, our carbon dioxide to have been removed from the body.

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So as we breathe in oxygen, the oxygenated blood leaves the lungs,
comes down towards the heart, coming in, so it has to be a vein,

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from the lungs the pulmonary vein into the atrium, down to the ventricle
and then leaving the heart via this vessel.

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So if we are coming out of the heart, it has to be an artery,
being the largest artery, it is known as the aorta.

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Feeding your body with that oxygenated blood, cellular respiration takes place
and as the waste product, the carbon dioxide, we have deoxygenated blood

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leaving the body's cells back to the heart into, so again, it has to be a vein,
the largest vein, so it is the venacava into the atrium,

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down to the ventricle and again coming out of the heart,
we see this vessel here, going towards the lungs so it is the pulmonary artery.

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And then the deoxygenated blood to the lungs you now breathe out the carbon dioxide.