Circulation

Question 1

Principles of Circulation

Answer 1

High surface area : volume ratio = diffusion is too slow alone
Blood transports substances (e.g., oxygen, nutrients, waste)
Circulatory system = heart + blood vessels + blood

Question 2

Roles of Blood

Answer 2

Transport: oxygen, carbon dioxide, nutrients, hormones
Protection: immune response (white blood cells, antibodies)
Regulation: body temperature, pH balance
Clotting: prevents blood loss (platelets, fibrin)

Question 3

Transporting Oxygen

Answer 3

Oxygen carried by haemoglobin in red blood cells
Forms oxyhaemoglobin in lungs (high O₂)
Dissociates in tissues (low O₂) to release oxygen
Affinity for oxygen changes depending on partial pressure

Question 4

Transporting Carbon Dioxide

Answer 4

CO₂ transported three ways:
- Dissolved in plasma
- As carbaminohaemoglobin (bound to haemoglobin)
- As hydrogen carbonate ions (HCO₃⁻)

Question 5

Blood Circulation

Answer 5

Double circulatory system:
- Pulmonary circulation: heart → lungs → heart (oxygenate blood)
- Systemic circulation: heart → body → heart (deliver oxygen)
Maintains high pressure for efficient transport

Question 6

The Human Heart

Answer 6

Right side = pumps deoxygenated blood to lungs
Left side = pumps oxygenated blood to body (thicker walls)
Valves (atrioventricular & semilunar) prevent backflow
Flow: vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta

Question 7

Tissue Fluid and Lymph

Answer 7

Tissue fluid: plasma without proteins, surrounds cells for exchange
At arterial end of capillary: high pressure forces fluid out
At venous end: lower pressure + osmosis draws fluid back in
Excess tissue fluid = drained into lymphatic system