With each beat, your heart pumps oxygen-rich blood throughout your body. Arteries carry this blood to your organs and muscles. Veins return oxygen-poor blood to the heart. This cycle works well when the arteries and veins are healthy.
A Healthy Artery
An artery is a muscular tube. It has a smooth lining and flexible walls that allow blood to pass freely. Active muscles need more oxygen, requiring increased blood flow. Healthy arteries can meet this need.
A Damaged Artery
If an artery is damaged, blood flow may be slowed or blocked. This means your muscles and tissues don't get all the oxygen they need. Plaque (PLAK), a buildup of fat and other materials, can start to form within the artery wall. At this stage, blood flows normally, so you're not likely to have symptoms.
A Narrowed Artery
If plaque continues to build up, the space inside the artery narrows. The artery walls become less able to expand. The artery still provides enough blood and oxygen to your muscles during rest. But when you're active, the increased demand for blood can't be met. As a result, for example, your leg may cramp or ache when you walk.
When You Have a Blockage
As you age, your arteries become stiffer and thicker—often called "hardening of the arteries." In addition, smoking, high cholesterol, and other risk factors can damage the artery lining. Plaque forms within the artery walls, narrowing the space inside and sometimes blocking blood flow. This process is called atherosclerosis.
A Blocked Artery
Plaque or a blood clot lodged in a narrowed section can block an artery. When this happens, oxygen can't reach the muscle below the blockage. Then you may feel pain when lying down (rest pain). This is especially common at night when you're lying flat. In time, the affected tissue can die, leading to the loss of a toe or foot.