3: EXCHANGE SYSTEMS AND MASS TRANSPORT - CARDIOVASCULAR DISEASE

Question 1

Describe the process of atherosclerosis

Answer 1

• damage occurs to the endothelium (inner lining of the artery)
• fatty streak forms (deposits of lipids and leucocytes clump under lining)
• atheroma forms (further leucocytes, lipids and connective tissue deposit and harden, forming a fibrous plaque
• atheroma blocks lumen, restricting blood flow and causing hypertension (high blood pressure)

Question 2

What is coronary heart disease?

Answer 2

a cardiovascular disease that occurs when atheromas form in the coronary arteries which restricts blood flow to the heart muscle

Question 3

Aneurysm

Answer 3

• balloon-like swelling of the artery
• starts with atheroma formation
• atheroma plaques damage and weaken arteries
• they also narrow arteries, increasing blood pressure
• when blood travels through a weakened artery at high pressure, it may push inner layers of the artery through the outer elastic layer to form an aneurysm
• the aneurysm may burst causing a haemorrhage (bleeding)

Question 4

Thrombosis

Answer 4

• formation of a blood clot
• starts with formation of an atheroma
• an atheroma plaque can rupture the endothelium of an artery
• this damages the artery wall and leaves a rough surface
• platelets and fibrin accumulate at the site of damage and form a blood clot (a thrombus)
• the blood clot can cause complete blockage of the artery/can become dislodged and block another vessel elsewhere in the body
• debris from the rupture can cause another blood clot to form elsewhere in the body

Question 5

Myocardial infarction (heart attack)

Answer 5

• if a coronary artery becomes completely blocked off, an area of the heart muscle will be completely cut off from its blood supply, receiving no O2 causing a myocardial infarction/heart attack
• can cause damage/death of the heart muscle
• if large areas of the heart muscle are affected, complete heart failure can occur which is often fatal

Question 6

What are the symptoms of a myocardial infarction?

Answer 6

• pain in chest and upper body
• sweating
• shortness of breath

Question 7

What are the risk factors for cardiovascular disease?

Answer 7

• high blood pressure
• high blood cholesterol and poor diet
• cigarette smoking

Question 8

Why is high blood pressure a risk factor for cardiovascular disease?

Answer 8

• increases risk of damage to artery walls
• increased risk of atheroma formation
• atheromas could also cause blood clots to form
• this could block blood flow
• anything that increases blood pressure increases the risk of CVD (eg: being overweight, excessive alcohol consumption etc.)

Question 9

Why is high blood cholesterol and poor diet a risk factor for cardiovascular disease?

Answer 9

• if blood pressure is too high (above 240 mg per 100 cm^3) the risk of CVD is increased
• this is because cholesterol is one of the main constituents of the fatty deposits that form atheromas
• increased risk of atheroma formation
• atheromas could also cause blood clots to form
• this could block blood flow

Question 10

Why is cigarette smoking a risk factor for cardiovascular disease?

Answer 10

• both CO and nicotine found in cigarette smoke increase risk of CVD
• CO combines with Hb and decreases amount of O2 available to tissues
• if the heart muscle doesn’t receive enough O2, it can lead to a heart attack
• smoking also decreases the amount of antioxidants in the blood which are important for protecting cells from damage
• fewer antioxidants means that cell damage in coronary artery walls is more likely which can lead to atheroma formation