Circulation and Blood Vessels

IGCSE Edexcel Biology
2.68-2.69 Blood Vessels and Circulation
Key Concept: Arteries, veins, and capillaries are adapted for their different roles in circulation.

Section A: Comparing Vessels

1. Compare arteries, veins, and capillaries (structure and function). [6]
2. Explain why capillaries have thin walls. [2]

Section B: System Overview

3. Describe the general structure of the circulatory system. [3]
Total marks: 11

Mark Scheme

1. Arteries: thick, elastic walls, high pressure; veins: thinner walls, valves, low pressure; capillaries: one cell thick for exchange (any six points) [6]
2. Thin walls shorten diffusion distance for gas and nutrient exchange [2]
3. Heart pumps blood through arteries to capillaries then returns via veins (pulmonary and systemic circuits) [3]