The human circulatory system is composed of blood, blood vessels, and the heart, working together to meet the metabolic demands of active tissues.
During prolonged physical exercise, blood plasma plays a vital role in transporting metabolic substrates and waste products. Name two substances, other than carbon dioxide, that are transported in the blood plasma during exercise.
Mature erythrocytes (red blood cells) are highly specialized for gas exchange. Describe two structural adaptations of an erythrocyte and explain how each adaptation maximizes the efficiency of oxygen transport.
The diagram below shows cross-sections of Vessel A (an artery) and Vessel B (a vein).
Using the diagram and your own knowledge, compare the structure of Vessel A (an artery) with the structure of Vessel B (a vein).