How Does Atherosclerosis Occur

Scientists believe that an initial injury must occur to the cell wall lining an artery to kick things off. Then a continual insult must occur to allow for

Figure 13.2 Injury to the wall of an artery allows LDLs and monocytes access to the intima. Monocytes become macrophages and smooth muscle cells also migrate into the intima. Both macrophages and smooth muscle cells engulf LDLs, especially after it is oxidized. Smooth muscle cells produce connective tissue proteins and calcium becomes deposited in the intima as well.

Figure 13.2 Injury to the wall of an artery allows LDLs and monocytes access to the intima. Monocytes become macrophages and smooth muscle cells also migrate into the intima. Both macrophages and smooth muscle cells engulf LDLs, especially after it is oxidized. Smooth muscle cells produce connective tissue proteins and calcium becomes deposited in the intima as well.

atherosclerosis to progress. The injury allows for monocytes to leave the blood and enter into the wall. The injured cells lining the artery release chemicals that signal monocytes to come in. Platelets arriving on the scene to patch the artery wall also release chemicals. Some of the chemicals encourage the relocation of smooth muscle cells from the media to the intima. More and more LDLs also move through the injury opening. So what we have is a mixture of stuff arriving in the intima and in excess of normal operations.

The monocytes, which are soon transformed into insatiably hungry macrophages, begin to ingest the LDLs in the intima. LDL can become modified (oxidized LDLs) by free radicals from cigarette smoke, environmental pollutants, foods, or produced in the body and macrophages find oxidized LDL most delicious. The ingestion of oxidized LDLs by macrophages gives them a foamy appearance when seen with a microscope and they are often referred to as foam cells. Furthermore, smooth muscle cells begin to release fibrous proteins into the area, and calcium-rich complexes also begin to accumulate. While all this is happening, new mono-cytes and LDLs continuously arrive on the scene from the blood and smooth muscle cells migrate from the media. So the process continues.

Atherosclerosis occurs within the walls of arteries and slowly reduces blood flow.

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