you see in lymph vessels, lots and lots of lymphocytes.
Well, let me just summarize what we have looked
at in this lecture on arteries, veins, capillaries,
and lymph vessels. First of all, it’s important
you understand the structure of arteries and
veins and you know the components of the wall
of these vessels. That you understand the
importance of elastic arteries, the aorta
in its recoil ability to maintain pressure
and therefore, flow inside the vessel.
It’s important to understand the structure of capillaries,
the three types of capillaries even though
I will emphasize those structures when we
look at them in more detail in other
organ systems. And finally, I want to let you know
that veins and lymphatic vessels have valves.
These valves stop the retrograde flow of blood,
as the blood and lymph pass along these vessels
on their way back to the heart. Movement of
blood and lymph occurs through these veins
and lymph vessels by the action of skeletal
muscles, so they’re forcing the blood along
and up the veins. So they have valves. So
finally, let me show you a party trick, a
trick that you can go to a party with and
impress your friends about your knowledge
of histology. If you look at your hands, the
back of your hand, and it’s probably more
obvious in my hand and yours, you can see
veins running back towards your shoulder along
your skin. Well, pick out one of these veins
and get two fingers and squeeze on the vein,
say near your your knuckles. And close off that
vein, so there’s no blood flow through it.
Then with the finger that’s closest to your shoulder,
squeeze that finger along the vein, so you’re
squeezing the blood up the vein. Then take
that finger away and have a look at the vein,
and I can’t see it here at all, because
the blood hasn’t flow back due to the
presence of valves stopping that retrograde
flow of blood. Well now take away that
finger, and immediately, the vein fills up
with blood. So that’s the illustration of
valves in veins. And as I said, that’s a
pretty good party trick to go and show off
with your friends your knowledge of histology.
So thank you very much for listening to
this lecture. I hope you’ve enjoyed it.