Explain how atherosclerosis develops and how it leads to coronary heart disease (8)

-Atherosclerosis: hardening of blood vessels (specifically those that withstand high blood pressure, ie arteries.)

• Blood vessels are composed of three layers: the tunica intima, tunica media and tunica adventitia. In a diet excessive in fats and LDL cholesterol, fat accumulates in the tunica intima. Macrophages (signalled by endothelial cells in the artery) are stimulated to engulf this fatty acid tissue. The macrophages will accumulate in this specific area and grow larger and larger. This is called an atheroma. Smooth muscle cells form a tough protective cap over the atheroma and the blood vessel lumen gets severely narrowed.

-Coronary arteries are the arteries supplying the heart muscle itself (which is working very hard to pump blood around the body hence requires large amounts of nutrients and oxygen). In coronary heart disease, the fibrous cap covering the atheroma will rupture (due to increased blood pressure- hypertension) in the coronary arteries. This will stimulate an immune response and many platelets will accumulate in the wound area and begin to form a clot so as to heal the wound. This clot completely blocks blood supply to the heart- the heart muscle is deprived of nutrients & oxygen, there is an accumulation of lactic acid which is toxic (from anaerobic respiration) and the heart muscle cells begin to die.