 In this video, I will describe the pathophysiology of atherosclerosis. Atherosclerosis is a specific subtype of arteriosclerosis. Arteriosclerosis refers to the hardening of arteries where it's more difficult for the arteries to stretch and recoil, which is a normal important function to be able to stretch out as they receive the blood coming from the heart and then recoil to continue to push the blood throughout the body. This elasticity of arteries does normally decline with age leading to some age-related arteriosclerosis, some hardening of the arteries, but atherosclerosis refers to a specific type of arteriosclerosis that involves the formation of plaques in the walls of the arteries. An atherosclerotic plaque includes a deposit of lipids in leukocytes and in minerals like calcium. The process of atherosclerosis is initiated with damage to the endothelium of a blood vessel. A variety of things could cause damage to the endothelium. Exposure to toxins is one of them. For example, we've learned that smoking tobacco increases the risk of atherosclerosis as the toxic chemicals from the inhaled smoke can damage the endothelium initiating this process of atherosclerotic plaque formation. Another risk factor that can damage the endothelium is hypertension and elevated blood pressure. As the endothelium becomes damaged, this is followed by inflammation. Inflammation will involve activation of leukocytes that come to the damaged endothelium and then they move into the wall of the endothelium. These leukocytes then will start to perform phagocytosis to engulf lipids. As the leukocytes are filled with lipids, they become trapped in the wall of the blood vessel contributing to the growth of the plaque. Then over time as the tissue of the endothelium and the surrounding smooth muscle is damaged, scarred tissue starts to form inside the plaque that is fibrous connective tissue is growing into replace the damaged muscle and epithelial tissue. Further lipids and leukocytes accumulate inside of the plaque as the plaque continues to grow and the plaque can also become mineralized and hardened. One of the minerals that's often found in atherosclerotic plaques at high concentration is calcium. Calcium can deposit within the plaque making the wall of the artery more stiff and rigid and hard. As the plaque continues to expand the lumen where blood flows through the artery is decreased or becomes more and more narrow, making it more difficult for blood to flow through the artery. Just having a narrowed artery as a result of atherosclerosis could contribute to increased blood pressure, making it more difficult for blood to flow through the blood vessels requiring a greater pressure to enable sufficient blood flow. This can also lead to an increased risk of blood clotting producing a thrombus or an embolism where a blood clot forms inside of a blood vessel and then it can break off and enter the circulation. So a thrombus forms inside of the blood vessel as a blood clot that starts to form and then as it breaks off and travels it's known as an embolus. Similarly, parts of the plaque could break off and travel as an embolist through the blood that then could get trapped in a smaller blood vessel forming an embolism that disrupts blood flow to an organ. If this occurs in a blood vessel carrying blood into the brain it could cause a stroke. Or if this restricts blood flow to the heart muscle by blocking one of the coronary arteries this could lead to a heart attack in myocardial infarct. So the risk factors for atherosclerosis include hypertension, high blood pressure, hyperglycemia, high blood glucose, infections, tobacco use, high blood lipid levels, especially cholesterol, but specifically it is LDL cholesterol, a specific subtype of the blood cholesterol known as low density lipoprotein cholesterol. And also obesity is a risk factor that contributes to atherosclerosis.