In this video I want to discuss the structures and the vessels of our large heart model.
And this is a very very good heart model.
It has much more information on it than your average introductory A and P student or even
human anatomy student would want to know.
But we don't have to list everything.
It's very good because it shows some things that the other models don't show.
But I've started a little differently on this one because I want to get across the four
chambers of the heart.
I have them open and then we will go back and retrace our steps.
Right ventricle, left ventricle.
Right atrium, left atrium.
Notice the thickness of the right ventricle versus the left ventricle.
Left ventricular wall much thicker than right ventricular wall.
Right ventricle has to pump blood to the lungs.
Left ventricle has to pump blood to the entire body.
Notice the walls of the atria, not thick at all.
They only have to pump the blood down into the ventricles.
Let's close the various chambers on this heart.
And I want to discuss the blood flow through the heart and the structures necessary to
follow that blood flow.
One thing good about this model, although they haven't necessarily colored arteries
and veins red and blue, they have put arrows indicating the direction of flow of the blood
and they have color-coded those arrows.
So you can see here there are blue arrows coming down toward the heart.
This is deoxygenated blood coming into the right atrium.
So if I hold this more in anatomical position we can see the right ventricle forms most
of the front of the heart.
And the heart is actually laying mostly on the right ventricle.
Above that, the right atrium with its auricle.
A little bit of the left ventricle forming the apex of the heart.
Notice we don't get to see the left atrium from an anatomical view.
You can see a little bit of the left auricle.
But we have to rotate this around to see the left atrium.
Now this heart is a little bit more realistic than the others.
Granted it is much too large but the heart is actually covered with a good amount of
fat.
And so this model represents the fat covering the heart.
And actually it probably doesn't have enough fat on it.
So when you are looking for the vessels on a real heart you do have to dig through the
fat.
Let's start with the blood flow into the right atrium, follow the blood flow through and
look at the various structures.
Blood entering the right atrium, we should know comes through the superior vena cava,
the inferior vena cava, and then through the coronary sinus system which we will outline
soon enough.
Right atrium with its right auricle.
If I open the right atrium we can look in the right atrium and we can see that the posterior
wall of the right atrium is very smooth.
Again that is embryologically venous tissue.
It is cardiac muscle but it is smooth wall.
Whereas the anterior wall of that right atrium is a very rough textured structure, and that
is called the pectinate muscle.
Or musculi pectinati.
Now if we look inside this right atrium we should be able to see the coronary sinus which
would be on this model, let me get the pointer in, down here, number 83.
The coronary sinus.
The opening of the coronary sinus.
Notice how close it is to the opening of the inferior vena cava.
We should also be able to see, in this region, the fossa ovalis.
Remember the adult structure left from the fetal remnant of what was the foramen ovale.
And we should be able to look down on the right atrioventricular valve.
Also known as the tricuspid valve.
We will pass into the right ventricle.
Let's look inside this right ventricle.
Now here we can see better the valve cusps of the right atrioventricular valve.
And those valve cusps are connected to these cords called chordae tendineae.
And those cords attach to papillary muscles.
On this model we've opened it up, but we have a good representation here of the papillary
muscles.
Remember inside the ventricle we have a latticework of cardiac tissue forming trabeculae carnae.
So this represents our trabeculae carnae.
And we have one special piece of the trabeculae carnae known as the septomarginal trabeculae.
On this model it is represented by number 63.
You can see it here and here.
If you use your imagination, if I put those two back together there would be a walkway
from the septum of the heart out to the margin of the heart, hence the name septomarginal
trabeculae.
Also known as the moderator band.
And as we leave this right ventricle we're going to go up through this smooth area known
as the conus arteriosus and into the pulmonary semilunar valve.
Once we pass through the pulmonary semilunar valve we are in the pulmonary trunk.
Let me close this portion of the model.
The pulmonary trunk is carrying blood, deoxygenated blood, out to the lungs.
And it will split into the left and the right pulmonary arteries.
Now the right pulmonary artery is going to pass behind the arch of the aorta.
So from an anterior view we cannot see that.
But I'll turn this around and we can see here the left, and the right pulmonary arteries.
Taking blood away from the heart, hence arteries.
But painted blue because they are carrying deoxygenated blood.
Once in the lungs we will unload the CO2 and we will oxygenated the blood.
The blood will turn a bright red color.
And we will return to the left atrium.
I going to turn this heart around so we can look at the left atrium.
Here's the left atrium in the back.
And we can see one, two, three, four pulmonary veins.
Again colored red because they are carrying oxygenated blood, but veins because they are
returning to the heart.
So here is our left atrium.
Remember from an anterior view you can't see the left atrium.
But I'm going to open the left atrium and with it we will take part of the pulmonary
trunk, and we can look inside the left atrium and we will see that is essentially smooth.
We can see a little bit of the backside of the fossil ovalis.
However, if I hold this at a different angle you can see there is some pectinate muscle
associated with this chamber.
It is not in the atrium itself.
It is rather up inside this earlike flap, the left auricle.
So there is some pectinate muscle associated with this chamber.
But not in the atrium itself.
Up inside the auricle.
From the left atrium we will pass down to the left ventricle.
We talked about the left ventricle a little bit earlier.
But here we can see the left atrioventricular valve.
Also known as the mitral valve or the bicuspid valve.
We can see the chordae tendineae.
We can see that they would attach to the papillary muscles.
We see that it's got a thick muscular wall, and it does still have the trabeculae carnae.
As we leave this left ventricle we're going to go up through the aortic semilunar valve.
Once we pass through that aortic semilunar valve we are going to be in the ascending
aorta.
I'm going to open this again and we will look at it from a different view.
I will try and hold the model so that it doesn't close itself.
We can look down, and I’ll tilt it a little bit, here is the pulmonary semilunar valve
and here we should be looking down on the aortic semilunar valve.
Notice the proximity to each other.
Now when we pass through the aortic semilunar valve we are then the ascending portion of
the aorta.
So right here we can see ascending aorta, then aortic arch, then the descending aorta.
And we can see nerve plexuses associated with it in the white.
We can see lymph nodes associated in the green and a few other structures that we will talk
about in just a second.
Last one I want to talk about before going into the coronary circulation is the other
fetal remnant.
Remember, pulmonary trunk, aortic arch.
In fetal life there was a ductus arteriosus connecting those two.
You don't need that after you are born.
It dries up.
It becomes the ligamentum arteriosum.
The ligamentum arteriosum.
The only thing left to cover on this heart is the blood supply to the heart.
The coronary circulation.
This model does an excellent job of depicting the coronary circulation.
I'm going to open the right ventricle so that we can just get a better view.
And I'm going to open the left atrium for a better view.
Coming from the ascending aorta, the very first branch of the ascending aorta, is the
right coronary artery.
Notice it circles around the right side of the heart in the sulcus between the right
ventricle and the right atrium.
Bring this back up.
And as it's passing along, we don't see it real well on this heart, there should be muscular
branches going down onto this right ventricle.
They are there but they are embedded in the fat pad.
As this right coronary artery circles around the right side of the heart it sends a branch
down along the margin of the right ventricle.
This is called the marginal artery.
Some books call it the marginal branch of the right coronary artery.
Hard to see because it is embedded in the fat pad.
Now this right coronary artery will continue to circle around in the sulcus, going around
the backside between the right atrium and the right ventricle and ultimately it will
come to the middle where it will join, or anastomose, with the circumflex coronary artery
to make a posterior interventricular artery, which passes between the right and the left
ventricle on the posterior aspect of the heart.
Now there are other branches and they are depicted on this model.
We don't generally discuss them in class but there are some branches that do go out onto
the atria and the auricle, but we're not going to talk about them.
Now let's follow the left coronary artery.
The left coronary artery is the second branch of the ascending aorta.
And on this model we can see here's ascending aorta, so here is the left coronary artery
passing behind the pulmonary trunk.
That's why I had to remove this portion.
As we get just past the pulmonary trunk that will branch.
It will become the anterior interventricular artery which supplies blood to the anterior
portion of both the right and the left ventricles.
And it will become the circumflex artery, some books call it the coronary circumflex
artery, which circles around the left side of the heart and eventually passes deep to
the great cardiac vein.
But it will travel around to anastomose with the right coronary artery to again help form
the posterior interventricular artery.
Along the way it sends out muscular branches.
Clinicians will have different names for these branches.
There is the left anterior descending and the right anterior descending.
We don’t teach the clinician terminology in our classes, we go with the anatomical
terminology.
So those are the blood vessels going out to the heart.
The coronary arteries.
The right coronary artery and its associated branches.
The left coronary artery branching into the anterior interventricular artery and the circumflex
artery and their associated branches.
The last thing I want to talk about is the venous return, the cardiac veins.
We start near the apex of the heart and travel upward and around the left side of the heart,
collecting blood from both the right and the left ventricles as the great cardiac vein.
And keep in mind veins run like rivers.
They get larger as they run because they pick up more and more tributaries.
So here we see the great cardiac vein running up and circling around the left side of the
heart in the sulcus between the left ventricle and the left atrium.
And it's getting larger as it runs.
As it passes the left side of the heart, and I will rotate the heart now, it will pick
up the marginal vein.
The marginal vein.
And then it continues to run.
There are some other veins that we don't teaching in class but if you're curious, this is the
oblique vein of the left atrium.
Great cardiac vein, marginal vein.
As it gets near the back of the heart, will pick up the middle cardiac vein and then head
toward the coronary sinus.
There is another vein coming in from the right side of the heart.
I will till this model just a little bit.
Here we can see it circling around passing very near the inferior vena cava.
This is the small cardiac vein.
It will pass by that inferior vena cava and join in with the great cardiac vein to form
this coronary sinus.
And then we return that venous blood into the right atrium of the heart.
On this model if we look at this right ventricle, now back in anatomical position, here we can
see the beginning of that small cardiac vein, buried within the fat pad.
And it will travel around and enter this sulcus and travel around the backside of the heart.
The last structures we talked about in the other videos are the anterior cardiac veins.
And I said that there are typically two anterior cardiac veins.
All of our other models have only shown one.
But here we can see one, and two anterior cardiac veins.
And if you look carefully you see that they cross over the sulcus between the right atrium
and right ventricle.
And they do not turn and run in that sulcus but rather go straight across superior to
the right coronary artery to enter directly into the right atrium.
These are the anterior cardiac veins.
So as I said before there are a lot of other things that we could learn on this model,
associated vessels, and things.
So this is a very good model, but I think we have covered most of the structures you
would be held responsible for.