6 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
LESSON B8 · EXPLAINER
Transport Systems and the Human Heart
Your heart beats about 100 000 times a day without you ever telling it to. How is it built for the job?
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Explore in 3D
The human heart in 3D
Watch the heart in 3D. Find the four chambers, the valves, and the vessels that enter and leave the heart.
Step 2 · Read
Key notes
Copy these into your notebook in your own words — that is how they stick.
Need for transport
Small SA:V ratio and large distances in multicellular organisms make diffusion too slow.
Thickest wall — generates high pressure to pump blood around the whole body.
Double circulation
Pulmonary (heart ↔ lungs) and systemic (heart ↔ body).
Arteries
Away from heart; thick elastic muscular walls; high pressure; no valves (except at base).
Veins
To heart; thin walls; wide lumen; valves.
Capillaries
One cell thick; site of exchange; form tissue fluid.
Pulmonary vs hepatic artery
Pulmonary artery: deoxygenated blood to lungs. Hepatic artery: oxygenated blood to the liver.
EXAM TIPS & COMMON MISTAKES
When drawing artery vs vein, show thicker muscle/elastic layer and narrower lumen in the artery.
Why the left ventricle is thicker: it pumps blood farther (whole body) at higher pressure — two clear points.
Hormones and amino acids are transported in animals; sucrose is transported in plants (P1 trap).
Step 2 · Learn from examples
Worked examples & study resources
The kind of support a teacher gives after the lesson: worked examples to attempt first, a board illustration, key terms, common misconceptions and memory aids.
Worked example 1
The path of blood through the heart
Trace the path of a red blood cell from the vena cava to the aorta, naming each chamber, valve and blood vessel in order.
Try it in your notebook first, then reveal the solution one step at a time.
Deoxygenated blood from the body enters the right atrium through the vena cava.
It passes through the tricuspid valve into the right ventricle.
The right ventricle pumps it through a semilunar valve into the pulmonary artery, to the lungs, where it picks up oxygen.
Oxygenated blood returns in the pulmonary vein to the left atrium, then through the bicuspid valve into the left ventricle.
The left ventricle pumps it through a semilunar valve into the aorta, to the whole body.
Answer. Vena cava → right atrium → tricuspid valve → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → bicuspid valve → left ventricle → aorta.
Examiner’s tip. Remember the diagram is drawn as if you are facing the person, so the heart’s left side is on the RIGHT of the page. Valves stop blood flowing backwards.
Worked example 2
Pulse rate before and after exercise
A student counts 18 pulse beats in 15 seconds at rest and 30 beats in 15 seconds just after running. (a) Calculate both heart rates in beats per minute. (b) Explain the change.
Try it in your notebook first, then reveal the solution one step at a time.
Beats per minute = beats in 15 s × 4.
At rest: 18 × 4 = 72 beats per minute.
After running: 30 × 4 = 120 beats per minute.
During exercise muscles respire faster and need more oxygen and glucose, and produce more carbon dioxide. The heart beats faster to deliver blood (oxygen and glucose) more quickly and to remove carbon dioxide.
Answer. (a) 72 bpm at rest; 120 bpm after running. (b) Muscles respire faster, so the heart pumps blood faster to supply more oxygen and glucose and remove more carbon dioxide.
Examiner’s tip. In “explain” questions link the heart rate to respiration in the muscles — that is the biological reason.
On the board · Arteries, veins and capillaries
Artery
Vein
Capillary
Direction of blood
Away from the heart
Towards the heart
Between arteries and veins, through tissues
Wall
Thick, muscular and elastic
Thinner, less muscle
One cell thick
Lumen
Narrow
Wide
Very narrow (one red cell wide)
Pressure
High, pulsing
Low
Falling
Valves
No (except at the heart exits)
Yes, to stop backflow
No
Job
Carry blood under pressure
Return blood at low pressure
Exchange of materials by diffusion
Arteries carry blood Away from the heart; veins bring it back; capillaries exchange materials with the cells.
Key terms
Atrium
Upper, thin-walled chamber that receives blood.
Ventricle
Lower, thick-walled chamber that pumps blood out of the heart.
Valve
Flap that keeps blood flowing in one direction.
Double circulation
Blood passes through the heart twice for every circuit of the body.
Pulmonary circulation
Heart → lungs → heart.
Systemic circulation
Heart → body → heart.
Capillary
Tiny vessel with walls one cell thick, where exchange takes place.
Common misconceptions
✗ Arteries always carry oxygenated blood.✓ The pulmonary artery carries deoxygenated blood. Arteries are defined by direction: away from the heart.
✗ Deoxygenated blood is blue.✓ It is dark red. Veins only look blue through the skin.
✗ The left ventricle is thicker because it pumps more blood.✓ Both ventricles pump the same volume. The left is thicker because it pumps blood all round the body at high pressure, not just to the nearby lungs.
Memory aid
LAB RAT: Left Atrium – Bicuspid; Right Atrium – Tricuspid. And Arteries go Away.
Real-life link
Hypertension (high blood pressure) is very common in the Caribbean. It makes the heart work harder and damages artery walls, raising the risk of heart attack and stroke — regular checks, less salt and exercise help control it.
Try this
Find your pulse at your wrist and at the side of your neck. Count beats for 15 seconds and multiply by 4. Compare with a family member.
Play & practise
Games
4 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness.
Step 3 · Practise
Paper 1 practice — multiple choice
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better.
Step 4 · Apply
Paper 2 practice — structured questions
Write full answers, then reveal the mark scheme and tick the points you earned (20 marks in total). Your answers are saved on this device.
Based on CSEC P2 January 2026 (hybrid), Question 1(c)–(d)
Question 1 [12 marks]
Arteries and veins differ in structure because they have different functions.
(a) Make large annotated drawings (or describe) the transverse sections of an artery and a vein, showing FOUR differences. [8]
MARK SCHEME — (a) (max 8)
(b) Explain why the pulmonary artery and hepatic artery are both arteries but function differently. [2]
MARK SCHEME — (b) (max 2)
(c) Explain why the left ventricle is much thicker than the right ventricle. [2]
MARK SCHEME — (c) (max 2)
Based on CSEC P2 May/June 2023, Question 4(a)
Question 2 [8 marks]
Organisms can be unicellular or multicellular.
(a) State ONE example of a unicellular organism and list THREE materials transported in multicellular organisms. [4]
MARK SCHEME — (a) (max 4)
(b) Explain why multicellular organisms need a transport system while unicellular organisms do not. Give TWO reasons. [4]
MARK SCHEME — (b) (max 4)
Your progress
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Sources
Where this topic appears in CSEC papers
Find these in your own past-paper booklets for extra timed practice. The practice above is adapted from them.
CSEC P1 May/June 2024 — Item 26 (artery vs vein for bypass surgery)