Atherosclerosis

• atherosclerosis: a disease of the arteries characterised by the deposition of fatty material on their inner walls.
• myocardial infarction is the death of cardiac muscle tissue due to a lack of oxygen (heart attack)
• ischemia is a condition in which blood flow (and thus oxygen) is restricted or reduced in a part of the body. Cardiac ischemia is decreased blood flow and oxygen to the heart muscle.
• angina: a condition marked by severe pain in the chest, often also spreading to the shoulders, arms, and neck, owing to an inadequate blood supply to the heart
• hypertension is high blood pressure
• stroke: a very serious condition where the blood supply to part of your brain is cut off
• atheroma (plaque) is a fatty material that builds up inside your arteries. (made of cholesterol, proteins and other substances that circulate in your blood)
• positive feedback occurs to increase/change the results.
• thrombosis: formation of a blood clot which either partially or fully block the blood vessels.
• atherosclerosis leads to myocardial infarction or stroke
• Atherosclerosis Stage 1:

  The endothelium becomes damaged and dysfunctional.

  The endothelial damage can result from high blood pressure, which puts an extra strain on the layer of cells.
• Atherosclerosis Stage 2:

  Once the inner lining of the artery is breached, there is an inflammatory response. White blood cells leave the blood vessel and move into the artery wall. These cells accumulate chemicals from the blood, particularly cholesterol. A fatty deposit builds up called an atheroma.
• Atherosclerosis Stage 3:

  Calcium salts and fibrous tissue also build up at the site, resulting in a hard swelling called plaque on the inner wall of the artery. The build up of fibrous tissue means that the artery wall loses some of its elasticity and hardens.
• Atherosclerosis Stage 4:

  Plaques cause the lumen of the artery to become narrower - making it more difficult for the heart to pump blood around the body and can lead to a rise in blood pressure. There is now a dangerous ‘positive feedback’ building up: Plaques lead to raised blood pressure and raised blood pressure makes it more likely for plaques to form, as damage to endothelial tissue in other areas becomes more likely.
• fibrin: a tough protein substance that is arranged in long fibrous chains.
• prothrombin: a protein produced by the liver that converts fibrinogen to fibrin
• platelets: small, colourless cell fragments in our blood that form clots and stop or prevent bleeding.
• fibrinogen: plasma glycoprotein synthesised by the liver and is the major structural component of a clot.
• plasma: a yellowish liquid in your blood that carries platelets, red blood cells and white blood cells around the body.
• thrombin: a protease that plays a physiological role in regulating homeostasis and maintaining blood coagulation.
• thromboplastin: the protein that activates the blood clotting system by binding to, and activating, the plasma serine protease.
• platelet plug: an aggregation of platelets formed during early stages of homeostasis in response to one or more injuries to blood vessel walls.
• Blood Clotting Step 1: Platelets stick to damaged wall and to each other, forming a platelet plug
• Blood Clotting Step 2: Thromboplastin is released from damaged tissues and platelets. This release triggers the clotting cascade.
• The Clotting Cascade:

  Step 1: Platelets and damaged tissue release a protein called thromboplastin.

  Step 2: Thromboplastin activates an enzyme that catalyses the conversion of the protein prothrombin into an enzyme called thrombin. A number of other protein factors, vitamin K and calcium ions must be present in the blood plasma for this conversion to happen.

  Step 3: Thrombin catalyses the conversion of the soluble plasma protein fibrinogen into the insoluble protein fibrin

  Step 4: A mesh of fibrin forms that traps more platelets and red blood cells to form a clot