Normal Blood Flow

In order to understand DVT, it is important to have some understanding of the normal blood flow around the body.

Many people get confused between the arterial circulation (blood flowing from the heart to the capillaries) and venous circulation (blood flowing back to the heart).

In in animation to the right, the human (or mammalian) circulatory system is shown.

Starting at the heart, and looking at the red blood on the right side of the picture:

Oxygenated blood (red) is pumped from the heart through the Aorta and then the arteries to the tissues.

The tissues use the oxygen and exchange it for carbon dioxide and the blood turns blue - deoxygenated blood.

The blue deoxygenated blood is pumped up the veins into the vena cava and then the heart.

Here it is then pumped into the lungs.

The lungs exchange the carbon dioxide for oxygen and the blood turns red again.

The newly oxygenated blood is pumped back to the heart and the process starts again.

Of note - all vessels taking blood AWAY from the heart are called Arteries.

All blood vessels taking blood towards the heart are called veins.

Therefore in the vessels going to and from the lungs (called the pulmonary circulation),
the arteries carry deoxygenated blood (blue) and the veins carry oxygenated blood (red).

This is the reverse from the normal situation.