A pump, a network and a living transport fluid
Core + labelled SupplementB9.1–B9.4Two 45-minute sessions + optional consolidationResponses save in this browser when storage is available. Download a copy before changing device. Nothing is submitted to MSH or a teacher.
Suggested pacing: Session 1: starter 5 min, learn/watch 25 min, activities 15 min. Session 2: retrieval 5 min, quiz 10 min, exam practice 25 min, exit ticket 5 min. Pause or split further to suit your class.
Many cells are far from exchange surfaces. Bulk transport delivers oxygen and nutrients and removes wastes; diffusion still occurs over short distances between blood and tissues.
The heart provides the pumping action, blood vessels carry blood, and valves keep flow in the correct direction. An artery carries blood away from the heart; a vein returns blood towards it. These names describe direction, not oxygen content.
| System | Route | Consequence |
|---|---|---|
| Fish: single | Heart → gills → body → heart | Blood passes through the heart once per complete circuit; pressure falls as it passes through gill capillaries. |
| Mammal: double | Right heart → lungs → left heart → body → right heart | Blood returns to the heart after the lungs and is pumped again before reaching body tissues. |
Double circulation allows relatively low pressure through delicate lung capillaries and higher pressure through the body. Oxygenated and deoxygenated blood are kept separate, supporting rapid oxygen delivery for aerobic respiration.
This is a schematic front view, not a realistic anatomical drawing. The person’s right appears on your left. Atria receive blood; ventricles pump it out. The septum separates the right and left sides. One-way valves prevent backflow. The left ventricle has a thicker muscular wall because it generates the higher pressure needed for the body circuit.
Coronary arteries run over the heart’s surface and supply the heart muscle itself with oxygen and nutrients. The heart muscle does not obtain all its oxygen simply from blood inside its chambers.
Atrial muscle contraction pushes blood into the ventricles. Ventricular contraction raises pressure, closing the atrioventricular valves and driving blood through the outlet valves into arteries. As the ventricles relax, the outlet valves prevent blood returning from the arteries. Valves open and close because of pressure differences; they do not actively pump.
| Vessel | Wall and lumen | Function / explanation |
|---|---|---|
| Artery | Thick muscular, elastic wall; relatively narrow lumen | Carries blood away at high pressure. Strong walls withstand pressure; elastic tissue stretches and recoils. |
| Vein | Thinner wall; larger lumen; valves in many veins | Returns blood at lower pressure. Wide lumen offers less resistance; valves help prevent backflow. |
| Capillary | Wall one cell thick; very narrow lumen | Exchange with tissues. Thin wall gives a short diffusion distance; extensive networks provide a large surface area. |
Structural descriptions are Core; explanations linking structure to pressure and exchange are Supplement. Capillaries allow oxygen and nutrients to reach cells and wastes to enter blood.
| Component | Identification clue | Main function |
|---|---|---|
| Red blood cell | Small biconcave disc; mature human cell has no nucleus | Haemoglobin binds oxygen for transport. |
| White blood cell | Nucleus visible; usually larger than a red blood cell | Defence through phagocytosis and antibody production. |
| Platelets | Tiny cell fragments | Help blood clot. |
| Plasma | Liquid surrounding cells | Transports cells, ions, nutrients, urea, hormones and carbon dioxide. |
A lymphocyte typically has a large, rounded nucleus occupying much of the cell; lymphocytes produce antibodies. A phagocyte often has a lobed nucleus and engulfs pathogens by phagocytosis. Blood clotting reduces blood loss and helps prevent pathogen entry.
Heart activity can be monitored by pulse rate, an ECG recording of electrical activity, and listening to the sounds of valves closing. During physical activity, heart rate usually increases.
Supplement explanation: working muscles respire faster, needing more oxygen and glucose and producing more carbon dioxide. Faster circulation supports delivery and removal.
Coronary heart disease involves narrowing or blockage of coronary arteries. Reduced blood supply limits oxygen delivery to heart muscle. Risk factors include diet, inactivity, smoking, stress, genetic predisposition, age and sex. Risk factors affect probability; one factor does not prove a person will develop disease.
A balanced diet, avoiding excessive saturated fat and excess energy intake, and appropriate regular activity can reduce risk. This is syllabus-level education, not an individual medical assessment.
Recognise the branching vessels on the heart’s surface. A blocked coronary artery can starve part of the muscular wall of oxygen, even while blood continues to pass through the heart chambers.
Cognito · Open on YouTube. Internet access is required. If your school blocks the player, use the written lesson below.
Cognito · Open on YouTube. Internet access is required. If your school blocks the player, use the written lesson below.
Follow one complete circuit. Blue and red are diagram conventions: human blood is never blue.
Use supplied data or a comfortable resting pulse count. Physical activity is optional and should only be undertaken under teacher guidance where appropriate. You can complete the entire lesson without exercising.
Heart rate = beats ÷ seconds × 60. A longer counting interval can reduce the effect of a one-beat counting error.
One mark per correct answer. Select all eight answers, then check. You may change answers and check again for practice.
Not yet checked
Original Cambridge-style practice, not copied past-paper questions. Write first, then reveal mark points and self-assess. Written answers are not automatically graded; self-scores are not official grades.
Suggested marking: one mark per valid point, up to 3.
Suggested marking: one mark per valid point, up to 3.
Suggested marking: one mark per valid point, up to 3.
Suggested marking: one mark per valid point, up to 3.
Illustrative supplied data for one volunteer. No exercise is required.
| Measurement | Heart rate / beats min⁻¹ |
|---|---|
| Resting | 72 |
| Immediately after activity | 132 |
| 1 min after activity | 108 |
| 2 min after activity | 90 |
| 3 min after activity | 78 |
| 4 min after activity | 72 |
Suggested marking: one mark per valid point, up to 2.
Suggested marking: one mark per valid point, up to 2.
Suggested marking: one mark per valid point, up to 2.
Suggested marking: one mark per valid point, up to 2.
Optional teacher-supervised work should offer a non-exercise alternative and respect health needs and privacy. Do not use these classroom data to diagnose fitness or disease.
This lesson follows Cambridge 0654 syllabus for exams in 2025–2027, B9.1–B9.4. The verified sequence after B6 is B7 Human nutrition, B8 Transport in plants, B9 Transport in animals. Check the examination-year syllabus for other cohorts.
Official topic order and video pages checked on 14 September 2026 (Bermuda). Embedded videos are hosted by YouTube and require internet access; playback depends on regional and school settings. All written learning, diagrams and activities work without a network connection.
Independent MSH teaching resource; not endorsed by Cambridge International. Scientific diagrams are original schematics, not to scale. Supplement labels identify Extended work; application boxes may include supporting explanation beyond the specified minimum.
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Continue the series: B7 Human nutrition · B8 Transport in plants · B9 Transport in animals