Name the main blood vessels to and from the heart, lungs, liver and kidneys.

Transport in Humans – Blood Vessels (IGCSE Biology 0610)

Learning objectives

• Describe the organisation of the human circulatory system (single vs double circulation) and the pressure differences between the two circuits.
• Identify the four chambers of the heart and the four main heart valves (tricuspid, mitral, pulmonary and aortic).
• Explain the structural differences between arteries, arterioles, capillaries, venules and veins and why these differences are important for blood pressure and exchange.
• List the main blood vessels that carry blood to and from the heart, lungs, liver and kidneys.
• Recall the major components of blood and one key function of each.
• Understand a simple clinical link (coronary heart disease) and basic preventive measures.
• Plan and interpret a basic practical investigation involving heart rate, pulse or blood pressure.
• Use the formula CO = HR × SV to calculate cardiac output from given data.

1. Overview of the circulatory system

The circulatory system is a closed network of vessels that transports blood, nutrients, gases and waste products throughout the body.

• Single circulation – found in fish: blood passes through the heart once per circuit (heart → gills → body → heart).
• Double circulation – found in mammals, birds and reptiles: the circuit is split into two loops.
  • Systemic circuit: oxygen‑rich blood leaves the left side of the heart, supplies body tissues and returns deoxygenated blood to the right side. High blood pressure is generated by the thick muscular walls of systemic arteries.
  • Pulmonary circuit: deoxygenated blood is pumped from the right side to the lungs, becomes oxygenated and returns to the left side. Low blood pressure is maintained by the thin walls of pulmonary arteries and the large capacitance of pulmonary veins.

2. The mammalian heart – structure and function

• Atria (right & left) – receive blood; walls are thin.
• Ventricles (right & left) – pump blood; walls are thick and muscular.
• Septum – divides right and left sides, preventing mixing of oxygenated and deoxygenated blood.
• Heart valves
  • Atrioventricular (AV) valves: tricuspid valve (right side) and mitral (bicuspid) valve (left side) – prevent back‑flow into the atria.
  • Semilunar valves: pulmonary valve (right side) and aortic valve (left side) – prevent back‑flow into the ventricles.
• Coronary arteries – supply oxygen‑rich blood to the heart muscle itself.

3. Blood‑vessel types – structure, function and relation to pressure

4. Main blood vessels to and from key organs

• Aorta – largest artery; carries oxygen‑rich blood from the left ventricle into the systemic circulation.
• Superior & Inferior vena cava – large veins; return deoxygenated blood from the body to the right atrium.
• Pulmonary artery (pulmonary trunk) – carries deoxygenated blood from the right ventricle to the lungs.
• Pulmonary veins – return oxygen‑rich blood from the lungs to the left atrium.
• Hepatic portal vein – transports nutrient‑rich blood from the gastrointestinal tract and spleen to the liver for processing.
• Hepatic veins – drain deoxygenated blood from the liver into the inferior vena cava.
• Renal arteries – branch from the abdominal aorta to supply each kidney with oxygenated blood.
• Renal veins – return deoxygenated blood from each kidney to the inferior vena cava.

5. Summary table – vessels “to” and “from” each organ

6. Blood – components and functions

7. Clinical link – coronary heart disease (CHD)

CHD occurs when atherosclerotic plaques narrow the coronary arteries, reducing the supply of oxygen‑rich blood to the heart muscle. Common risk factors include:

• High‑fat, high‑sugar diet
• Smoking
• Physical inactivity
• Obesity and high blood pressure
• Family history of heart disease

Prevention: balanced diet, regular aerobic exercise, avoiding tobacco, maintaining a healthy weight and regular health checks (blood pressure, cholesterol).

8. Practical/experimental skills (AO3)

Investigation – Effect of exercise on pulse rate and blood pressure:

1. Measure each student’s resting pulse (beats per minute) and blood pressure (mm Hg) using a sphygmomanometer.
2. Students perform a 5‑minute moderate‑intensity activity (e.g., jogging in place).
3. Immediately after exercise, re‑measure pulse and blood pressure.
4. Record data in a table, calculate mean values and discuss the physiological reasons for any changes observed (e.g., increased sympathetic activity, vasoconstriction of arterioles).

Key skills practiced: use of a stopwatch, sphygmomanometer, accurate data recording, calculation of averages, and drawing evidence‑based conclusions.

9. Mathematical requirement (AO2)

Cardiac output (CO) is the volume of blood the heart pumps each minute.

Formula: CO = HR × SV

• HR = heart rate (beats per minute)
• SV = stroke volume (≈70 mL per beat for an average adult)

Example: HR = 75 bpm → CO = 75 × 70 ≈ 5 250 mL min⁻¹ (≈5 L min⁻¹).

10. Suggested diagram

Quick revision checklist

1. What artery leaves the left ventricle? Aorta
2. Which veins return blood to the right atrium? Superior & Inferior vena cava
3. Which vessel carries blood to the lungs? Pulmonary artery
4. Which vessels return blood from the lungs? Pulmonary veins
5. What is the special vein that supplies the liver? Hepatic portal vein
6. Which veins drain the liver? Hepatic veins
7. Identify the artery and vein of each kidney. Renal artery & renal vein
8. Recall the three main components of blood and one function for each.
9. State one major risk factor for coronary heart disease and one preventive measure.
10. Write the formula for cardiac output and explain each term.