In this lecture, you are going to learn about
the histological structure of the heart.
Hopefully at the end of this lecture, you’ll have
a very good understanding of what endothelium
is. That you’ll understand the structure of
the heart and how blood flows through the
heart. And how the pumping of the heart is
controlled by the impulse conducting system,
and how Purkinje fibres are able to distribute
impulses through the heart muscle.
It’s important that you understand the difference
between Purkinje fibres which are normal cardiac
muscle fibres but specialized for conduction,
how to distinguish those fibres from cardiac
muscle that specialize to pump, to contract,
and move blood through the heart. It’s also
important you understand the difference
between the structure of cardiac muscle and
smooth muscle and skeletal muscle. Now, it’s very,
very important that you understand endothelium.
Endothelium has an enormous number of functions
throughout the body. And each of these functions
will be dealt with in more detail in other
parts of the body systems. But endothelium
forms a very thin lining of all the blood
vessels in our body. It has a very important
function of being a barrier, and only allowing
certain substances to pass across the wall
of this very, very small thin epithelial lining
of all blood vessels. Of course, the heart
is structured in such a way that it’s able
to pump blood, first of all, to the lungs
to be oxygenated, to then receive that blood
back and pump that oxygenated blood to the
rest of the body. So the structure of the
heart is a very important concept structure
to understand. It’s also very important to
understand the sequence of blood flow through
the heart because as I said a moment ago,
the heart is structured in such a way that
the sequence of blood flow through the heart
is highly coordinated. And without that proper
sequence of blood flow from the heart, then
we would not have the ability to oxygenate
our blood and to carry oxygenated blood to
the rest of the body. First of all, let’s
explain or let’s clearly understand what
we mean by the term endothelium.
Endothelium is a very special name given to the
epithelial lining throughout the cardiovascular system.
It’s the thin epithelium that is in contact
with the lumen of the blood vessels and even
the lumen of the heart, that consists of a
very flattened squamous epithelial cell.
And they’re also very tightly bound to each
other because one of the jobs of endothelium
is to be a selective barrier for transport
across the epithelial surface. But endothelial
cells also have an enormous number of other
functions. Some of those functions I’ve
listed on the left-hand side of this slide.
And I’ll refer to these functions in later
lectures when I deal with their function in
different organ systems.