00:00
So, again, let’s talk a little bit about
one of the other structures in the heart that’s
important- the coronary arteries. The coronary
arteries are like the fuel line in your car.
00:10
If you don’t have a good open fuel line
and gasoline doesn’t get in or diesel fuel
doesn’t get in your motor, you know what
happens- the motor doesn’t function. The
same is true about the heart. It needs oxygenated
blood to nourish it and to enable it to continue
to do its mechanical activity. And the heart
is a remarkable organ. Remember it beats constantly,
has to continue beating of course, if you
want to stay alive. Sometimes for many, many
years, 80, 90 years, sometimes even a 100 years.
It’s a remarkable, strong muscle that is
very resistant to injury except when certain
diseases occur, but in fact, often tries to
do its best job even when injured. So, there
are, of course, two main coronary arteries
- there is the left coronary artery and the
right coronary artery. You say to me, “Wait…
wait… wait a minute, my uncle had a triple
coronary bypass. Where is the third coronary
artery?” The third coronary artery occurs
because the left coronary artery branches
early on after its origin. It branches into
the left anterior descending coronary artery
and the left circumflex coronary artery. So,
what are we talking about here? We are talking
then about two main arteries that start, but
one very quickly divides into two main branches
so that’s how we have the three coronary
arteries that are talked about.
01:32
We are going to come back and talk more about
the coronary arteries and I am going to show
you some pictures from a CAT scan, but let’s
take a look inside the heart for a moment.
01:41
I wanted to just reiterate the return of venous
blood to the heart. What you are seeing here
is a little diagram of the inside of the right
atrium and you will notice that there are
three circles, and these three circles represent
the venous drainage coming into the heart.
02:00
The highest one, the one that’s up top,
is the entrance of the blood from the superior
vena cava, that blood enters the right atrium
and drains the venous blood from the upper
part of the body. Now, if you look at the
second one just below that, that’s the one
from the inferior vena cava that’s draining
blood from the bottom of the body. So, what’s
the opening there on the right hand side?
That’s the coronary sinus, that’s the
heart’s venous system coming back in, because
of course the heart’s getting oxygenated
blood, it has to have venous return to the
heart so it returns also to the right atrium.
02:37
So, upper part of the body, the lower part
of the body and the heart all drain into the
right atrium and then of course, they pass
through the tricuspid valve into the right
ventricle, they are pumped to the lung where
the blue blood becomes red as it takes on
oxygen and gives off carbon dioxide.
02:55
So, here we are back to the coronary arteries-
and this is actually a CAT scan that shows
you… it’s colorized by the way. These
are artifical colors put in to make it look
realistic. But in fact, you can see very clearly
the coronary arteries here. You can see the
right coronary artery, the left anterior descending,
and the left circumflex. The right coronary
artery supplies the right ventricle, part
of the septum- the wall between the left and
right ventricles and part of the back of the
heart. The left anterior descending coronary
artery supplies the front of the heart and
part of the septum. And the left circumflex
coronary artery supplies the lateral wall
of the heart and also part of the back of
the heart. And of course, blockage in any
one of these can cause a myocardial infarction
or a heart attack. Here you see, the CT in
its natural state- not colorized artificially,
but you can see very clearly the coronary
arteries coming off the left, the right, the
anterior descending and the circumflex.
03:58
So, we have reviewed the heart anatomy. The
one thing we haven’t talked about is the
pericardium. The pericardium, of course, is
the constraint. It’s the plastic bag, if
you will, that keeps the heart nicely shaped
within the chest, doesn’t allow it to over
expand and protects the heart as well. It’s
filled with a little bit of fluid so that
the heart is able to move smoothly within
the pericardium. When disease happens to the
pericardium and it becomes thickened or weeps
fluid into that space, then of course we can
have restriction of heart function and we
are going to talk about pericardial diseases
as we go along.
04:37
Well, that was a quick run through cardiac
anatomy. You see a few references here that
can help you to read a little more about it.
I would like to reiterate what I have done
here is given you a very quick view, if you
will, like in an airplane from 35,000 feet. If
you want to have a little more detailed look
at the ground, you need to do some more reading
to… more fully understand the cardiac anatomy.
We are looking forward now to the next lecture,
where we are going to talk about the function
of the heart, that is it's physiology.