In this video I want to discuss the features and the vessels of our medium size heart model.
This is a pretty good model for most of the structures.
Again we are looking at this model from an anterior view, a good anatomical view.
So we see that the heart is mostly resting on the right ventricle.
A little bit of left ventricle down here, and the interventricular septum.
We can see the right atrium.
And of course we have to pivot the heart around to the backside, because we've seen in the
other videos, that the left atrium is actually a posterior structure of the heart.
And we'll talk about that left atrium more a little bit later.
Let's go back to the anterior view of the heart and follow the blood flow as it comes
into the heart.
Remember the right side of the heart responsible for collecting the deoxygenated blood from
the body.
So here we can see the superior vena cava entering into the right atrium.
If I rotate this, down here we can see inferior vena cava entering into the right atrium.
We have the right atrium, and a little ear like appendage on the top known as the right
auricle.
If I open this right atrium we should be able to look inside and we should be able to see
that in the wall between the right and the left atrium there is a depression known as
the fossa ovalis, and we also see down here by the opening for the inferior vena cava,
the opening of the coronary sinus.
This model depicts it very well.
Notice the posterior portion of this right atrium is very smooth.
That is because embryologically it was venous tissue.
But the anterior surface of the atrium is made of a rough textured surface that is known
as pectinate muscle or musculi pectinati.
Also if I turn this medially you should be able to see, slightly from this view, the
top of the valve that separates the right atrium and the right ventricle.
That is known as the right atrioventricular valve.
I will remove the anterior surface of this heart and we can take a look inside the right
ventricle.
Here we can see the valve cusps of that right atrioventricular valve, also known as the
tricuspid valve.
We can see that those valve cusps attach to tenderness chords known as chordae tendineae.
And those cords in turn attach to little projections of muscle arising from the ventricle wall
known as papillary muscles.
Also notice on this model that the ventricular wall is made of a latticework of meat like
tissue, and I can hold up the other portion and we can see this woven latticework.
That is called the trabeculae carneae.
Trabeculae carneae literally means a latticework of meat.
On one of our other models we have already seen it, but notice this structure right here
that appears to be cut off.
Coming from the interventricular septum of the heart and its heading this way out towards
margin of the heart.
On the other half of this model here is where it would attach.
So this connects to this.
Put it back on and it makes sort of a walkway across that right ventricle.
That is known as the septomarginal trabeculae.
We talked about it in another video, but going from the septum of the heart out to the margin
of the right ventricle, so septomarginal, and it's part of our trabeculae carneae, so
septomarginal trabeculae.
Also known as the moderator band.
Very important in the conduction of impulses through the heart for ventricular contraction.
Now notice on this model, I'm going to skip forward just a little bit, the thickness of
the right ventricle versus the thickness of the wall of the left ventricle.
The right ventricle is thicker than the right atrium because it has to pass blood all the
way through the lungs.
Not a long distance, but about 3000 miles worth of capillaries.
Whereas this left ventricle is going to pump to the entire body, about 60,000 miles worth
of capillaries.
So it needs a much thicker muscular wall.
Going back to this right ventricle, as we leave the right ventricle we are going to
go up and out.
And we are going to go through a smooth area of the right ventricle known as the conus
arteriosus.
And that will lead us into our pulmonary trunk.
There is a valve at the beginning of the pulmonary trunk known as the pulmonary semilunar valve.
That prevents blood from coming back from the pulmonary trunk into the heart.
Once you leave the heart you want to that blood to stay out of the heart.
This pulmonary trunk will divide into right and left pulmonary arteries.
Now keep in mind they are blue on this model because they are carrying deoxygenated blood.
But we call them arteries because they are going away from the heart.
So here's pulmonary trunk.
At this point it divides, and we’ll turn this around and follow, into the left and
the right pulmonary arteries.
Now if we think back to our fetal circulation, remember that between the pulmonary trunk
and the arch of the aorta there was a structure in the fetus known as the ductus arteriosus.
It dries up in the adult and forms a ligamentum arteriosum.
And on this model here you can see this little white structure, ligamentum arteriosum.
The remnant of the fetal ductus arteriosus.
We've gone out to the lungs.
We collect oxygen and we get rid of CO2.
And we return to the heart via one, two, three, four pulmonary veins.
Now keep in mind these are veins because they are headed back toward the heart but they
are red on this model because they are carrying oxygenated blood.
Now if I open this left atrium we can see the openings for the pulmonary veins in this
left atrium and we can see the backside of the fossa ovalis.
We don't usually name it in the left atrium.
It is a feature of the right atrium.
But here we see a real good view looking down on the left atrioventricular valve.
Also known as the mitral valve or the bicuspid valve.
Now if I turn this back around to a somewhat anterior view we can see that that atrioventricular
valve also has tendinous chords, the chordae tendineae, which attach to papillary muscles.
And we also see the trabeculae carneae.
We do not see a septomarginal trabeculae in the left ventricle.
Remember the left ventricle is going to pump blood to the entire body out through the aorta.
Here we can see the beginning of the ascending aorta at the aortic semilunar valve.
So we'll pump from the left ventricle through the aortic semilunar valve through the ascending
aorta, aortic arch, descending aorta.
Let's talk about a few of the blood vessels associated with the aorta, and then the cardiac
circulation.
Off of the aortic arch we have three vessels.
The first branch of the aortic arch is called the brachiocephalic trunk.
That vessel will branch to supply the right side of the head and neck and the right upper
extremity.
The second branch of the aortic arch is the left common carotid artery.
It will supply the left side of the head and neck.
The third branch of the aortic arch is the left subclavian artery.
It supplies blood to the left upper extremity.
Now I want to talk about the circulation to the heart itself.
Coronary arteries.
Cardiac veins.
There are two coronary arteries.
And on this model we only actually see one.
The very first branch from the ascending aorta, right here, is the right coronary artery.
Notice the right coronary artery is going to travel in the sulcus between the right
atrium and the right ventricle, and travel around to the posterior side of the heart
on the right.
Along the way that right coronary artery will send out some muscular branches.
So here's some muscular branches.
And as it is passing the right edge of the heart or margin of the heart it sends out
what is called the marginal artery.
The marginal artery.
Some books call it the marginal branch of the right coronary artery.
Then this right coronary artery will continue around the right side of the heart where it
may form, by itself, the posterior interventricular artery.
Or it may anastomose with the circumflex coronary artery which has also formed a posterior interventricular
artery.
So that is the pathway of the right coronary artery.
Now on this model we don't get to see the left coronary artery.
It passes posterior to the pulmonary trunk.
So it's hidden behind the pulmonary trunk, not removable on this model.
But right about at this point, at the tip of my pointer, it divided, and it became the
anterior interventricular artery, supplying blood to both the right and left ventricles.
The other branch was the coronary circumflex artery.
Some books just call it the circumflex artery.
It circles around left side of the heart.
And as it is circling it sends out muscular branches.
And ideally it will circle around and join with the right coronary artery to form the
posterior interventricular artery.
So that's blood supply out to the heart tissue.
Now we need to have venous return from the heart tissue back to that right atrium, where
all venous return goes.
The largest vein of the heart is called the great cardiac vein.
It starts near the apex of the heart and runs upward and toward the left on the heart following
the interventricular septum.
And it is draining blood from a little bit of the right ventricle and a lot of the left
ventricle.
It will then circle around the left side of the heart.
Keep in mind this is the great cardiac vein.
And like a river, the further it flows the more tributaries it picks up the larger it
gets.
The great cardiac vein circling around the left side of the heart.
As it's passing the left border of the heart it will pick up what is known as the marginal
vein.
So the great cardiac vein going around the left side of the heart picking up the marginal
vein.
Then it continues, continues and it will pick up in the middle cardiac veins.
And it is not uncommon to have two veins rather than one.
So on this model they indicate the two middle cardiac veins.
And then it heads into coronary sinus.
But before it becomes coronary sinus it picks up one other vein.
We need to go back and talk about that.
We've seen it on some of the other models.
Draining the lower portion of the right ventricle we have the small cardiac vein.
The small cardiac vein looks as though it is headed toward the right atrium but just
before it gets to that right atrium it will turn and travel in the sulcus between the
right atrium and the right ventricle past the inferior vena cava and enter into that
coronary sinus system.
So here we have the great cardiac vein, it has already picked up the marginal vein.
Picks up the middle cardiac veins, the small cardiac vein, from that point on we are coronary
sinus going into the right atrium.
The only other vessel we need to discuss on this model then is what is known as anterior
cardiac veins.
I'm going to open the right atrium on this model and you can see draining the upper portion
of the right ventricle a vein that goes over the top of the right coronary artery and directly
into the right atrium bypassing the system of the coronary sinus.
This is called the anterior cardiac vein.
This model shows one.
In most people there are two anterior cardiac veins.
Those should be all of the structures that you should be able to find on this model.