If we looked inside the chest cavity,
we would see the lungs
and pericardium,
which is the fibrous covering of the heart.
We could also see the heart beating.
Here are the left and right coronary arteries.
They supply blood to specific regions of the heart.
If either is damaged or blocked,
it could injure the heart wall.
In a healthy artery,
red blood cells flow through unimpeded.
But if the inner wall is damaged,
cholesterol plaque can build up.
This progressively narrows the space
through which blood flows.
Eventually,
the artery may become too narrow
for clotted blood to pass through.
If it does,
the artery could become completely blocked.
That would cause a lack of oxygen,
or ischemia,
in the part of the heart the artery supplies.
The result is a heart attack,
known as a myocardial infarction.