In order to understand Deep Vein Thrombosis and the other things that can cause clots in the veins, we must have some understanding of how the blood flows around the body.
The 2 sorts of blood vessels that carry blood around the body are the Arteries and the Veins.
Blood containing oxygen is pumped out of the Heart into Arteries.
The arteries are thick walled vessels that take the blood from the heart to the extremities - down the arms and legs to the hands and feet.
The walls of the arteries have 3 main layers and a special lining that is contact with the blood.
The most important layer for us to note is the Media which is a thick muscle layer. It is the Media give the arteries the "bounce" that let them return to their normal shape after the heart has pumped blood through them at high pressure.
You can feel this "bounce" in some areas of the body such as at the wrist - this is called the "Pulse" (see the animations below to understand how the pulse comes from the heart pumping blood through the arteries).
The Endothelium is the innermost part of the layer called the Intima. The Endothelial cells are as single layer of cells that are in contact with the blood.
They have special substances on their surface that stop the blood from clotting on them in normal circumstances.
