In this video I want to cover some of the features and the blood supply of one of our
older heart models.
This is actually a very good heart model.
It has had a little bit of abuse over the years, but a very good heart model especially
in the vasculature.
First I want to just go over the major features of the heart.
We know that it has four chambers.
And this is an anatomically correct anterior view of the heart where we see that the heart
is lying mostly on the right ventricle.
The apex of the heart, the tip of the left ventricle, is to the left and down.
And we can see here the right atrium with its right auricle, the ear like appendage.
A little bit of left ventricle, and from this true anatomical position you really shouldn't
be able to see the left atrium.
It is hidden behind the pulmonary trunk and the rest of the heart.
But you can see a little bit of the left auricle coming over that left side.
Now if I turn this heart around so that we can see the backside, now you can see this
entire pink area, from here to here, is the left atrium.
So anatomically it is actually on the posterior aspect of the heart when viewed in anatomical
position.
Now keep in mind with the heart all deoxygenated blood is returning into this chamber.
The right atrium.
So here we can see the superior vena cava entering into this right atrium.
And if I turn it around here a little we can see the inferior vena cava are entering into
that right atrium.
Here's the right atrium with it’s right auricle, superior vena cava, inferior vena
cava it.
If I turn this and open this right atrium a little bit, we can see inside the right
atrium and the features that we discussed in the video where we did the lecture of the
heart.
Here we can see the representation of the fossa ovalis.
The fossa ovalis, remember it is a feature of the right atrium.
And down here we can see this red spot is supposed to be on this heart, the opening
of the coronary sinus.
Now if I tilt this heart a little bit forward you can see that that opening of the coronary
sinus is located fairly near where the inferior vena cava opens into that right atrium.
We put this back on the stand.
Keep in mind that we leave this right atrium and we’re are going to go into the right
ventricle.
The right ventricle of the heart is separated from the right atrium of the heart by an atrioventricular
valve.
The right atrioventricular valve.
Also known as the tricuspid valve.
However on this model it has been somewhat abused over the years so the valve itself
is missing.
If I turn it this way you should be able to see the three cusps of the valve in this opening.
However those cusps have been long since removed from this heart.
However, we learned in class that those valves attached to tendinous cords called cordae
tendineae.
And that is represented by the strings here on the model that would have gone up to the
valve cusps had they still been here.
And the other end of those cordae tendineae are attached to these little pink like projections
leaving the wall of the ventricle, known as papillary muscles.
Also we see that the inside wall of this ventricle and we can see it here as well, is a rough
texture.
That rough textured wall inside the ventricles is known as trabeculae carnae.
Now this model doesn't show it well but we have the same thing inside the atria, however
there it is known as pectinate muscle, or musculi pectinati.
We will see that on another model.
So on this model so far we have looked at the right side of the heart.
The right atrium and it's various features.
Keep in mind it has a very thin muscle wall.
It only has to pump blood down into the right ventricle.
Right ventricle has a much thicker wall than the right atrium.
We see the trabeculae carnae.
We see the papillary muscles.
And we see the tendinous cords, cordae tendineae.
This right ventricle is going to pump blood up through the pulmonary semilunar valve.
And if I tilt this model slightly you should be able to see in here a pulmonary semilunar
valve.
We will see it from above in a moment.
As we reach the top of that right ventricle we reach a smooth area that leads into this
structure, the pulmonary trunk.
That smooth area is known as the conus arteriosus.
So we have collected the deoxygenated blood in the right atrium.
Sent it to the right ventricle.
We've learned the features of both.
From this right ventricle we go up through the pulmonary trunk.
Keep in mind this is now an arterial structure, but its blue because of our pulmonary circuit.
And then it will divide to go to both the right lung and the left long as the pulmonary
arteries.
So if I close these chambers and rotate this model around we can see here this pulmonary
trunk heading out this way as the left pulmonary artery and on this side as the right pulmonary
artery.
After we have been through the left side of the heart and through the lungs we then become
oxygenated blood.
Remember oxygenated blood is bright red.
So the oxygenated blood will return to the heart via one, two, three, four pulmonary
veins.
Remember in this case the veins are red because they are oxygenated blood, but veins because
they are going toward the heart.
And we already discussed that this is the left atrium of the heart.
So here's the left atrium receiving those four pulmonary veins.
And here we can see, on top of the left atrium, the left auricle.
From the left atrium the blood will go down into the left ventricle.
We're going to open this for just a second so we can look into the left atrium.
You should inside the left atrium be able to see the opening of the four pulmonary veins,
one, two, and on this side three, four.
Otherwise the left atrium is fairly uneventful for us.
And then we go down through the left atrioventricular valve, which would have been here between
the left atrium and ventricle, but again on this model has been long since removed.
The left atrioventricular valve, also known as the bicuspid or mitral valve.
And then inside the left ventricle we will see again the rough textured muscle wall,
the trabeculae carnae, papillary muscles and cordae tendineae going up to the valve cusps.
Keep in mind that this left ventricle is going to pump blood to the entire body so it needs
a very thick muscle wall.
They've done a pretty good job on this model of showing this thick muscle wall of the left
ventricle.
From the left ventricle we will pump up through the aortic semilunar valve.
So if I tilt the model you can look upward into where we are going to head into the aorta.
But now if I bring it down this way we can see the top of the aortic semilunar valve
in the beginning of the ascending aorta.
And here we can see the top of the pulmonary semilunar valve in the pulmonary trunk.
If I put this structure back on we will then see the aortic arch passing up over the top
of the pulmonary trunk and mostly the right pulmonary artery and then down as descending
aorta.
So those are the main structures, features of the heart we can see on this model.
But what I want to cover next on this model is, this is probably one of the best models
we have for these structures, is the coronary circulation.
The blood vessels to the heart itself.
The blood to the heart actually comes from two vessels, the right coronary artery and
the left coronary artery.
And both of those come off of the ascending portion of the aorta.
So I'm going to open his right atrium again and show you here we have the ascending aorta
leading into the aortic arch.
The very first branch of the ascending aorta is the right coronary artery.
It travels in a sulcus between the right atrium and ventricle.
And it goes around the right side of the heart.
And as it is a passing the right side of the heart it is going to send some muscular branches
down onto the upper part of the right atrium.
Then it's going to circle around the right aspect of the heart.
And as it does so it is going to send an artery along the very edge of the right side of the
right ventricle.
That is called the marginal artery.
Here it is kind of hard to see because its laying right next to a vein.
We will address the vein here in a second.
Then that right coronary artery continues along the backside of the heart where it reaches
approximately the middle of the heart and forms what is known as the posterior interventricular
artery.
Now in different individuals it works a little bit differently.
Ideally the right coronary artery would meet with another artery called the circumflex
artery and form one posterior interventricular artery.
But often the right coronary artery will form a posterior interventricular artery, which
again is hard to see on this model because of the vein in the way.
And another posterior interventricular artery formed by the coronary circumflex artery.
So this is a variation on the theme.
So we follow the right coronary artery.
Let's recap right coronary artery for just a second.
It is the first branch of the aorta.
But keep in mind not the aortic arch, the ascending aorta.
So right coronary artery, muscular branches.
As it goes along of the very right edge of the right ventricle it sends off the marginal
artery.
Then it continues around the backside of the heart to help form the posterior interventricular
artery.
The left coronary artery also leaves the ascending aorta, maybe an eighth of an inch after the
right coronary artery.
So it is the second branch of the ascending aorta.
So here we can see our ascending aorta and our left coronary artery.
Notice on this model that left coronary artery actually passes behind the pulmonary trunk.
So had I not removed this piece of the model we could not see that left coronary artery.
It only runs for about an inch, then it splits into the anterior interventricular artery,
which will run downward on the front of the heart along the interventricular septum.
So dividing the right and left ventricles.
So here we see our anterior interventricular artery.
The other branch is called the circumflex artery.
Some books refer to it as the coronary circumflex artery.
It circles around the left side of the heart and ultimately will help form posterior interventricular
artery.
And along the way it has muscular branches that serve mainly the left ventricle.
Now there are some other branches that do serve the atria but most of these models do
not address those branches.
So that's the blood supply to the heart.
The right and the left coronary arteries and their various branches.
Now I want to address blood supply from the heart itself back to the heart.
The heart is living tissue.
It used oxygen.
It is going to have venous drainage.
Remember all of that venous drainage is heading toward the right atrium.
Near the apex of the heart we will start small, and as we flow, it's like a river, the further
it flows the more tributaries it picks up.
We will see the great cardiac vein.
So here we will see the great cardiac vein draining the anterior surfaces of the right
and left ventricles and then it travels up and circles around the left side of the heart.
It will travel in the groove between the left ventricle and the left atrium.
As it is traveling around the left side of the heart it picks up the marginal vein and
then it continues traveling along to the backside of the heart in the groove between the left
atrium and left ventricle.
As it passes along the left side of the heart and it circles around to the back it will
pick up a large vein on the posterior aspect of the left ventricle called the left posterior
ventricular vein.
Then it continues onward toward that right atrium.
Just before reaching the right atrium it is going to pick up a large vein which runs up
the backside of the heart, known as the middle cardiac vein, which is draining along the
interventricular septum on the posterior portion of the heart.
So getting blood from both right and left ventricles.
The middle cardiac vein.
So, so far we have seen the great cardiac vein picking up the marginal vein and then
picking up the middle cardiac vein.
And then we're going to become coronary sinus and go into the right atrium.
But we have another vein we're going to pick up before we get there.
So let me put this back on the stand for a second.
The other vein that we pick up along the way drains the lower portion of the right ventricle.
It is called the small cardiac vein.
Of all of the models we have in this lab this model is the best one for representation of
the small cardiac vein.
The small cardiac vein drains along the right margin of the right ventricle, enters the
sulcus between the right atrium and the right ventricle, and then turns and travels around
the back side of the heart passing very near, passing very near the inferior vena cava,
and then entering into that coronary sinus right next to this middle cardiac vein.
So at this point we have the great cardiac vein which has already picked up the marginal
vein and the posterior, the left posterior ventricular vein, the middle cardiac vein,
then the small cardiac vein.
Now we have coronary sinus which will go into that right atrium.
There is one last venous structure that I want to talk about on this model.
Because it's a little bit different than everybody else.
This is called the anterior cardiac vein.
There are usually two.
This model only shows one.
Anterior cardiac veins drain the upper portion of the right ventricle.
But they do not enter into this venous circulation that we have seen so far, but rather they
drain directly into the right atrium.
So here you can see this anterior cardiac vein passing across the top of the right coronary
artery to enter directly into this right atrium.
So it does not get involved in the system with the coronary sinus.
So those are the blood vessels of the heart you can see on this model.
This is one of the better models for the blood vessels of the heart.
I will show you blood vessels on the other models and we will discuss the discrepancies.