that dissolve the blood clot.
Here is an example of atheroma under the microscope.
You can see all these little what look like
needles and little, round holes. All of those
are accumulation of cholesterol in the artery,
and mixed in there is lots of scar tissue.
And you can see that this material is under
the tunica intima—that is, the top layer
of the arterial wall that's right up against
the channel. In this picture, you can actually
see the little white needles where there had
been cholesterol crystals collected in this
atherosclerotic plaque. Now, sometimes, an
embolus will travel in the bloodstream and
get stuck at a point where there is atherosclerotic
narrowing of the blood vessel, and when that
embolus causes obstruction, again, you can
start to have death of tissue beyond that.
So there's two kinds of pathophysiology here
(abnormal physiology): the atherosclerotic
process and then the blood clot process. And
the two of them often interact to cause a
lot of symptoms and even fatal illness.
So let's take an example of atherosclerosis.
Let's take the carotid artery. Here, in this
little cartoon, you see narrowing, or constriction,
of the inner surface, the lumen—that is,
the channel of the carotid artery. And this
is almost always caused by atherosclerosis.
This accounts for 25% of all strokes, and
the stroke can also be the result of embolization
from the left atrium in atrial fibrillation,
as we said. That's also a common cause of
stroke. Detection by physical exam of the
narrowing is very poor. I mentioned before:
Sometimes you'll hear a bruit or a turbulent
blood flow, a sort of "ch—ch—ch" when
you put your stethoscope over the neck. But
often, there's no sound, and the only way
to detect it is with, usually, an ultrasound
And you can see, in this little cartoon, there
is a narrowing in the carotid artery which,
if that became severe, patients might start
to have symptoms: brief symptoms where they
lose their ability to speak, or where their
hand becomes lame or numb and then it gets
better. Eventually, when there's a complete
blockage in that artery, the stroke won't
get better. So in the lower extremity, that
in the legs, as I mentioned before in the
basic series, patients develop so-called intermittent
claudication—that is, intermittent pain
and cramping while walking that goes away
with rest. Why does that happen? Because during
walking, the muscle requires more blood flow.
And then, when not enough blood flow gets
through, the muscle starts to give a signal
of pain. When the patient stops, the blood
flow gets through again, the muscle demand
goes down, and the pain goes away. When the
atherosclerotic narrowing in the legs is severe,
you can start to get some severe changes in
the leg, such as hair loss or shiny, thin
skin. And eventually, you may even have death
of tissue, usually of the toes—blackened
areas—and I'll show some pictures later
of areas of gangrene on the toes and the fingertips.