Tuesday, January 15, 2002

What is Arteriosclerosis?

Arteriosclerosis is such a big word, but if we break down the word, maybe we can understand what it means. Arterio is what doctors call anything that deals with arteries, or the blood vessels that carry blood away from the heart; doctors use the word sclerosis when talking about something hardening. So when a doctor says the word arteriosclerosis, they mean hardening of the arteries. An artery affected with arteriosclerosis has fatty streaks, which are white or yellow lines down the middle of the artery. By age 25 most Americans have a fatty streak present in one or more of their major arteries. Fatty streaks are typically larger and more numerous in individuals with high cholesterol diets. Anything high in animal fat is considered to be high in cholesterol.

Cholesterol needs to be carried in the blood so that cells throughout the body can get the cholesterol for their membranes and steroid production (a cell's surface is called a membrane.). Cholesterol mixes with blood like oil mixes with water. In order for it to be carried in blood, it must be carried by a lipoprotein, which is a combination of a lipid (like fat) and a protein. The lipoprotein can carry cholesterol because one side of the molecule likes blood and the other likes cholesterol so a bunch of these lipoproteins surround the cholesterol while it is carried in the blood. The process of getting the cholesterol-carrying lipoprotein to the cells goes wrong with arteriosclerosis.

To understand how arteriosclerosis affects an artery we must first look at what makes up an artery. Going from where the blood is in the artery and moving out, arteries are composed of special skin cells, muscle cells, and connective tissue with skin cells. The skin cells in your arteries are not the same as the skin cells on your arm, but they do protect and form a barrier just like the skin on your arm. The skin cells inside your blood vessels, scientifically known as endothelial cells, serve as a sort of filter between the blood and the cells. Part of the way they filter the blood is by taking in only specific components of the blood.

One of these components is the cholesterol-carrying lipoprotein called low-density lipoprotein, or LDL for short. The endothelial cell pushes the cholesterol out of the other side of the cell, away from the blood side. Cholesterol then gets 'stuck' in between the skin and muscle layer. Neighboring cells and other cholesterol-carrying LDL molecules join the stuck cholesterol and the fatty streak grows. In addition to other cells and cholesterol-carrying LDL molecules, calcium can deposit in the fatty streaks. The presence of calcium causes the arteries to become hard and rigid. Typically our arteries are elastic and can stretch to help keep our blood pressure constant. When arteries become hard and cannot stretch, our blood pressure can increase. This is one of the reasons why doctors, nurses, and physician assistants keep track of our blood pressure so they can tell when it has gone up.

As the fatty streak grows and the artery becomes more and more rigid, the opening for the blood to move through become smaller and smaller. Sometimes total blockage can occur arteries. The fatty streaks can also burst when they become large and broken off parts can block small arteries. When arteries are blocked, a stroke or heart attack can occur. This is why arteriosclerosis is a major health concern in America. The arteries most prone to fatty streaks are the ones that supply blood to the heart (coronary arteries) and to the head.

For more information on arteriosclerosis, visit the Vascular Disease Foundation's website at http://www.vdf.org.