Blood delivers nutrients and oxygen to the tissues and carries metabolic waste products away from the tissues. Healthy arteries are usually elastic and have clear, smooth internal surfaces. However, under certain conditions the arteries, including the coronary arteries, become thickened and stiff and the internal surface becomes lined with fatty deposits. These deposits called plaque start as early as childhood and become thicker as an individual ages. To understand the process which causes the arteries to become blocked by developing plaque, it is essential to know about cholesterol and how it travels in the bloodstream.
Cholesterol is a normal part of all body tissue, and is essential for life.
Cholesterol travels to body tissues in the bloodstream in tiny droplets, surrounded with a protein shell or coat. These droplets, called lipoproteins, transport cholesterol to and from body tissues. It is normal to have some LDL in the bloodstream. However, when the level of these lipoproteins become excessive, the cholesterol they contain will be deposited on the arterial walls. This causes plaque formation and a narrowing of the vessels.