Explain the effect of a partly blocked coronary artery on the human body.

The coronary arteries are the blood vessels that supply the heart muscle itself with oxygen and glucose. 1. **Reduced Blood Flow:** A blockage (caused by a build-up of fatty material, called an atheroma) narrows the lumen of the artery, restricting blood flow to the cardiac (heart) muscle. 2. **Reduced Supply of Reactants:** This means the heart muscle cells receive less oxygen and glucose. 3. **Impact on Respiration:** Oxygen and glucose are the reactants for aerobic respiration. With a reduced supply, the rate of aerobic respiration in the heart muscle cells decreases. 4. **Energy Deficiency:** Since aerobic respiration is the process that releases energy (in the form of ATP), less energy is available for the heart muscle to contract. 5. **Consequences:** To compensate, the heart muscle may start to respire anaerobically. This is less efficient and produces lactic acid, which can cause chest pain (angina). If the artery becomes completely blocked by a blood clot forming on the atheroma, the cells are completely starved of oxygen and will die. This is a heart attack (myocardial infarction) and can be fatal.