CIE iGCSE Co-Ordinated Science B9.3 Blood vessels Exam Style Questions Paper 4
Question
(a) Fig. 10.1 shows a cross-section through a vein when seen under a light microscope.
(i) On Fig. 10.1 draw two label lines to identify the:
- lumen
- wall of the vein.
▶️Answer/Explanation
Labeling instructions:
1. Lumen: Central empty space where blood flows
2. Wall: Outer layered structure surrounding lumen
Key features: • Vein walls are thinner than arteries • Lumen typically appears collapsed in microscope slides • Contains valves (though not visible in cross-section)
(ii) Name one structure of veins not visible in Fig. 10.1.
▶️Answer/Explanation
Valves
Valve function: Prevent backflow of blood, especially in limbs against gravity
(b) Explain why the wall of an artery is much thicker than the wall of a vein.
▶️Answer/Explanation
1. Pressure: Arteries withstand higher blood pressure from heart contractions
2. Elastic tissue: More smooth muscle/elastin to accommodate pulse surges
3. Structural need: Maintain shape under pressure (veins can collapse)
Physiological difference: Arterial blood pressure ~120/80 mmHg vs venous ~10 mmHg
(c) Coronary heart disease is caused by a blockage in the coronary arteries. State two lifestyle factors that increase the risk of coronary heart disease.
▶️Answer/Explanation
Primary risk factors: 1. Smoking (damages artery linings)
2. High-fat diet (leads to atherosclerosis)
3. Lack of exercise
4. Chronic stress
5. Obesity
Mechanism: These promote plaque buildup (atheroma) in coronary arteries
(d) Hormones are released into blood.
(i) Name the hormone that
- is released in stressful situations
- decreases the glucose concentration of the blood.
▶️Answer/Explanation
Stress hormone: Adrenaline (epinephrine)
Glucose-lowering hormone: Insulin
Physiological roles: • Adrenaline – “fight or flight” response from adrenal medulla
• Insulin – promotes glucose uptake by cells from pancreas
(ii) Auxin is a plant hormone. State the effect of auxin on plant cells.
▶️Answer/Explanation
Primary effect: Promotes cell elongation (in shoots)
Additional roles: • Apical dominance • Phototropism/gravitropism • Root initiation • Prevents leaf abscission
Mechanism: Softens cell walls by activating proton pumps