00:00
right chest, little bit upper left chest,
lower right chest and lower left chest.
00:01
So, let’s talk a little bit about the parts
of the heart. The heart, of course, is a muscle
pump. So, that’s the most important part
but that’s not the only part. Of course,
you have to have valves to keep the blood
flowing in the right direction. If in fact,
you didn’t have valves, all the blood would
just slosh back and forth within the heart.
00:22
You have to have the valves to keep the blood
flowing in the right direction. You also have
electrical wiring, we are going to talk a
lot more about this, but in fact, what triggers
the contraction of the heart is an electrical
signal that starts high in the right atrium
of the heart with a little automatic pacemaker
and passes right down through the heart muscle
and results in contraction of the heart muscle
when the electrical signal gets there. Of
course, you also have to have arteries to
supply the heart with oxygen and nutrients
so it can work. In other words, the fuel line
for the heart to put the fuel into the heart
cells so that they can contract. The veins are also
important because they carry the
tired blood- the blood that’s lost its oxygen
and some of its nutrients and is carrying
waste products, it returns to the right atrium
along with the superior and inferior vena
cava to be circulated again from the right
ventricle into the lungs to gain oxygenation
and to give up its carbon dioxide. And then,
of course, the entire heart is contained in
a membrane, a very tough membrane called the
pericardium that protects the heart, particularly,
for example, from infections in the lungs,
should they occur and it also keeps the heart
in a nice shape so that it doesn’t expand
too much when it’s working.
01:39
The important lesson here in anatomy is that
the heart is a muscle pump, that it’s going
to continue to pump blood in a continuous
circle through the body and that it is meticulously
and beautifully adapted to do this. We will
be talking about more detail of the various
ways that the heart does this. So, here is
the diagram again that you saw before, once
more to reiterate, venous blood comes back
to the right atrium through the tricuspid
valve to the right ventricle, out the pulmonary
artery, back. Oxygenated blood comes back
to the left atrium through the pulmonary veins
through the mitral valve and then pumped out
the aortic valve to the body.
02:24
Well, let’s look in a little more detail
inside these various chambers. Here you see
a diagram inside the right ventricle and you
can see… of course, it shows you the blood
is blue, that’s the deoxygenated blood.
You can see the right atrium above the right
ventricle and you can see the pulmonary artery
and the pulmonary valve below it. There are
a variety of abnormalities that the heart
can be found in… in infants. For example,
the pulmonary valve can be stenotic or closed,
has to be fixed at the… early in life, there
can be holes in the heart, for example, a
connection between the right and left ventricle
where there should be none. All of these are
the area of the pediatric cardiologist who
can make those diagnoses very early in life
and often these days, infants are operated
on and have these abnormalities corrected.
But, the normal right ventricle, remember,
will be separated from the left ventricle
with a muscle septum that will prevent blood
from the right side from getting on to the
left side. When blood from the right side
gets onto the left side, the patient actually
has a faintly bluish tinge to themselves and
you… we will talk about that when we talk
about physiology and diagnosis.
03:46
Here we see a diagram of the right ventricle
contracting and as I said before, the right
ventricle is working like a bellows, you will
see in the diagram on the left, that’s the
contracted right ventricle and then on the
right, you can see the filling right ventricle.
04:01
It looks like a bellows, right? Just like
the blacksmith’s bellows that’s used to…
to heat up the fire beneath the horseshoes
that the blacksmith is working on. The right
ventricle again, is thin walled and much
thinner walled than the left ventricle because
it pumps at a much lower pressure than the
left ventricle.
04:22
Here we see a diagram of blood that is passing
through the heart and the different pressures
in the different chambers. We are going to
be talking a lot more about this when we come
to the physiology component, but its important
to see right here on the left hand side of
the diagram, low pressure in the right atrium,
then periodic high pressure followed by low
pressure in the right ventricle. Then we see
in the pulmonary artery, high pressure followed
by not such low blood pressure, and then the
pulmonary capillaries which are a reflection
of left atrial pressure, also a low pressure
about the same as the minimal pressure in
the pulmonary artery. We see that the blood
passes through the heart starting at a very
low pressure in the right atrium, the tricuspid
valve opens, blood flows into the right ventricle
and it squeezes and then you see the pressure
going up for the right ventricle. And then
when the… the pulmonary valve closes, the
pressure falls again down to the baseline
where the righ-… the tricuspid valve opens
again and the blood flows into the right ventricle.
05:31
Out in the pulmonary artery, when the pulmonary
valve closes, the pressure no longer falls
anymore and you see a… a sort of baseline
pulmonary artery pressure that’s transmitted
across to the pulmonary capillaries and eventually,
to the pulmonary veins and the left atrium.