In this video I want to discuss the structures and the features and the blood vessels of
one of our smaller heart models.
Now this is a pretty good heart model for some structures.
Some of the others are a little misleading.
So I'll talk about the misleading things as we go through.
Again as we've seen in the other heart models we are going to have four chambers.
And this is an anatomical view, so we're looking mostly at right ventricle and right atrium
with the right auricle.
And we see a little bit of the left ventricle.
So keep in mind the heart is laying on the right ventricle on top of the diaphragm.
Now if I turn this heart around we can see that the left atrium is actually a posterior
structure of the heart, with its one, two, three, four pulmonary veins entering into
the atrium.
Let's go back to the right atrium and start with the blood flow through the heart.
On this model we can see the superior vena cava coming into the top of the right atrium.
And if we tilt it a little we can see and inferior vena cava coming into the bottom
of the right atrium.
Collecting blood to send it to the right ventricle so that we can go to the lungs.
Now if I open is right atrium and right ventricle we can see inside the right atrium.
And we see that the posterior aspect of this right atrium is very smooth.
But on this model they show us a little bit, in color but not in actual texture, rough
texture to the front of this right atrium.
The rough textured muscle in the front of the right atrium is known as pectinate muscle,
or musculi pectinati.
The other features we should be able to see inside this right atrium, on this model this
white spot here represents the fossa ovalis, and this dark spot here represents the opening
of our coronary sinus.
Also notice how thin the wall of the right atrium is.
Because it is only going to pump the blood down to the right ventricle.
On this model we have good representation of the right atrioventricular valve.
Also known as the tricuspid valve.
That tricuspid valve is connected to tendinous cords called chordae tendineae.
And those tendinous cords come down and attached to projections coming up from the ventricular
wall known as papillary muscles.
Here we see a papillary muscle.
Should be a papillary muscle attached here, but we removed that part of the model so that's
the papillary muscle here.
Another papillary muscle back in the distance.
Now keep in mind inside the ventricle the wall is a fairly rough texture and if I hold
up the anterior portion of this heart and we look inside, a rough texture to the ventricular
walls.
That rough texture is known as trabeculae carneae.
Trabeculae carneae.
One last feature I want to point out inside this right ventricle before we head out to
the lungs is this feature right here.
This is a special piece of the trabeculae carneae.
It's been cut off right here.
We can actually see the other portion of it on this part of the model right there.
It is spanning from the interventricular septum and it will go across to the wall of the right
ventricle.
It is known as the septomarginal trabeculae.
Named because it goes from the septum to the margin of the heart.
And it's part of the trabeculae carneae.
So the septomarginal trabeculae.
Also known as the moderator band.
Very important in conduction impulses for contraction of this right ventricle.
Remember blood in the right ventricle is going to be pumped to the lungs.
So the right ventricle has a thicker wall that the right atrium.
And as we go up out of the right ventricle into our pulmonary trunk we are going to pass
through a smooth area of the right ventricle known as the conus arteriosus.
That will lead us to a valve in the pulmonary trunk known as the pulmonary semilunar valve.
So here we see the pulmonary semilunar valve.
Then we pass up through the pulmonary trunk.
The pulmonary trunk will divide to go to both the right and left lungs as pulmonary arteries.
So let me put the front of the heart back on, and I’ll pivot this around and you can
see the pulmonary truck came up and divided into left and the right pulmonary arteries.
Now along the way, remember we talked about fetal life, the pulmonary trunk is associated
with a structure that shunted blood between pulmonary trunk and the aorta in the fetus.
That was the ductus arteriosus.
But remember in the adult it dries up and becomes a ligaments structure that we can
find between the pulmonary trunk and the arch of the aorta.
On this model it is right here.
This is a ligamentum arteriosum.
The ligamentum arteriosum.
Pass through the pulmonary arteries, we go to the lungs.
We pick up oxygenated blood, or we oxygenate the blood, we blow off the CO2, and then we
return to the left atrium of the heart through one, two, three, four pulmonary veins.
Remember, veins because they are returning to the heart.
But in this case they are red because they are carrying oxygenated blood to the left
atrium.
We bring this back around to the front we can now see the auricle which projects off
of the left atrium.
Now I'm going to open his heart back up again and we can look inside that left atrium.
The left atria the inside is fairly uneventful.
You can see the backside of the fossil ovalis.
But we don't name it in the left atrium.
And then you can see the opening of these pulmonary veins.
Between the left atrium and the left ventricle we have another valve known as the left atrioventricular
valve.
Also known as the mitral valve.
Also known as the bicuspid valve.
That valve is very similar to what we saw on the right side of the heart.
It's going to have chordae tendineae.
Those chordae tendineae are going to pass down and attach to these smooth muscle projections.
I don't want to imply they are made of smooth muscle.
They are smooth looking, they are still made of cardiac muscle, known as papillary muscles.
We still see trabeculae carneae.
From the left ventricle we're going to pass the blood up through the aortic semilunar
valve and through the ascending aorta, the arch of the aorta, the descending aorta, and
the various branches out to the entire body.
That means that the wall of this left ventricle must be much more muscular than the other
chambers of the heart because it has to pump through about 60,000 miles worth of capillaries
in the human body.
So the left ventricle.
A thicker wall.
Still has the trabeculae carneae.
We see the papillary muscles and the chordae tendineae.
We see the aortic semilunar valve.
Then we are going to pass up through the ascending aorta, the aortic arch, and then the descending
aorta.
Off of the aortic arch we see three vessels that are going to supply everything head,
neck, and upper extremity.
The first branch of the aortic arch is called the brachiocephalic trunk.
It will supply the right side of the head and neck and the right upper extremity.
The second branch of the aortic arch is called 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 will supply the left upper extremity.
Those are the major features of this model.
Now I want to go back and look at the coronary circulation on this model, because it's a
little different than the other models.
Keep in mind, if you look at the other videos, the heart is supplied by two coronary arteries.
The right coronary artery and the left coronary artery.
The right coronary artery was the first branch off of the ascending aorta and it traveled
around the right side of the heart in the groove between the atrium and the ventricle.
So here we can see the right coronary artery and it's muscular branch.
And then it sends a branch down along the very edge of the right ventricle called the
marginal artery.
I'm going to remove this from the stand, we will circle around the backside of the heart,
still right coronary artery.
That right coronary artery will reach to the middle of the back of the heart where it will
be either join with the circumflex artery and make a single posterior interventricular
artery.
Or it may curve down and make a posterior interventricular artery on its own.
So here we see the right coronary artery comes around and circles down to form, on this heart,
one of two posterior interventricular arteries.
So a quick recap, right coronary artery from the ascending aorta.
Circling around the right side of the heart, with a muscular branch, then a marginal branch
and circling around the back to help form posterior interventricular artery.
Now on this model, I'll set us back on the stand briefly, we do not get to see the left
coronary artery, except for one very small portion.
Remember the left coronary artery is going to leave the ascending aorta, pass behind
the pulmonary trunk.
On this model the pulmonary trunk is not removable so we do not get to see that portion of this
vessel.
However if we remove the remainder of the heart, right here, this is what we get to
see of the left coronary artery as it was passing behind the pulmonary trunk.
At this point on this model it will divide.
And then we can go to this portion of the model and follow it.
We can see it, I'm going to turn this around, right here.
This matches this.
So this is left coronary artery.
This is left coronary artery.
Right here the coronary artery divides and becomes the anterior interventricular artery
and one that circles around the left side of the heart, the circumflex coronary artery.
So left coronary artery on this model passed behind the pulmonary trunk, branches right
here at this point into the anterior interventricular artery with it's muscular branches, and the
coronary circumflex artery, which circles around the left side of the heart, sends off
miscellaneous muscular ranches, and on this particular model, let's remove it from the
stand again, will come around the left side of the heart and ideally should join the right
coronary artery to form posterior interventricular artery.
But in this case turned and formed its own posterior interventricular artery.
That is not uncommon at all.
So most of this is laid out pretty well.
But there is some exceptions that I want to show.
This model does not represent them quite the way they should be.
Let me put the model back on the stand.
In a previous video we saw that there was an anterior cardiac vein draining blood from
the upper portion of the right ventricle directly into the right atrium.
And textbook wise there really should be two.
Well this one shows two going in there, however this is an anterior cardiac vein.
This one is a misrepresentation of the small cardiac vein.
The small cardiac vein comes toward that right atrium, appears to be headed toward the right
atrium but then when it gets to the groove between the atrium and ventricle it will run
in this groove, or sulcus, and it will run along with the right coronary artery and circle
around, and we’ll remove this again, and circle around, and they show it here passing
by the inferior vena cava to head toward the coronary sinus.
That is the small cardiac vein.
So here we had an anterior cardiac vein.
Here we have small cardiac vein.
But very much misrepresented on this heart.
It should come here and then turn and go around.
This almost implies that it is going into the right atrium.
That is not true.
Now the other vessels we need to see on this heart, we've seen before in the other video.
Great cardiac vein coming up along the anterior Interventricular septum, draining portions
of the right and left ventricle.
Then it will circle around the left side of the heart.
As it circles the left side of the heart it will pick up the marginal vein.
And it will continue in the groove or the sulcus between the left atrium and the left
ventricle.
Remove this from the stand again.
So great cardiac vein picks up the marginal vein as it's headed toward the coronary sinus.
It will pick up one or two middle cardiac veins, as well as the small cardiac vein that
came around from the right ventricle.
All of those enter the coronary sinus and then that carries the blood into that right
atrium so that all of the venous blood is returned to the right atrium either via the
coronary sinus or the anterior cardiac veins.
I believe that that is all of the structures that you would be held responsible for on
this particular model.