Learn · Biology · Class 10

Transport in Humans

The double pump, the pipes, and why the left side of your heart is thicker.

8 parts
Scroll to begin ↓
📘 DefinitionWhy a transport system is neededPart 1 of 8
The heart — a double pumpright atriumright ventricleleft atriumleft ventriclethickest wallto the lungsto the whole bodyfrom bodyfrom lungs
Four chambers. The left ventricle wall is thickest because it pumps to the whole body.
🔍 In detailThe three vesselsPart 3 of 8
✏️ Worked exampleWhat blood is made ofPart 4 of 8
🌍 In the real worldHeart disease, and what causes itPart 5 of 8
⚠️ Common mistakesWhere marks get lostPart 6 of 8
✅ SummaryWhat to rememberPart 7 of 8
✏️ Worked exampleWatch one worked throughPart 8 of 8
1📘 DefinitionPart 1 / 8

Why a transport system is needed

A single cell can rely on diffusion. A human cannot, the distances are far too great and the surface-area-to-volume ratio far too small.

So we have a circulatory system: a pump, a network of vessels, and a fluid to carry things.

It is a double circulation, blood passes through the heart twice for each complete circuit: once to the lungs, once to the body. That keeps the pressure high enough to reach every cell.

2🧩 The partsPart 2 / 8

The heart

Four chambers: two atria on top receive blood, two ventricles below pump it out.

  • Right side, receives deoxygenated blood from the body, pumps it to the lungs.
  • Left side: receives oxygenated blood from the lungs, pumps it to the whole body.

The left ventricle wall is much thicker, because it must generate enough pressure to reach your toes and your brain. The right only has to reach the lungs, which are next door.

Valves prevent backflow, so blood moves one way only.

3🔍 In detailPart 3 / 8

The three vessels

  • Arteries: carry blood away from the heart. Thick muscular elastic walls, narrow lumen, high pressure, no valves.
  • Veins: carry blood towards the heart. Thin walls, wide lumen, low pressure, and valves to stop backflow.
  • Capillaries: one cell thick, so substances diffuse in and out. This is where exchange actually happens.

Define arteries and veins by direction, not by oxygen. The pulmonary artery carries deoxygenated blood, and the pulmonary vein carries oxygenated blood, the exceptions that catch people out.

4✏️ Worked examplePart 4 / 8

What blood is made of

Red blood cells: carry oxygen using haemoglobin. Biconcave for surface area, and with no nucleus so there is more room for haemoglobin.

haemoglobin + oxygen ⇌ oxyhaemoglobin

The reaction is reversible: it picks oxygen up where concentration is high (lungs) and releases it where concentration is low (respiring tissue).

White blood cells, defence. Phagocytes engulf pathogens; lymphocytes produce antibodies.

Platelets: trigger clotting, sealing wounds and keeping pathogens out.

Plasma: the straw-coloured liquid carrying dissolved food, CO2, urea, hormones and heat.

5🌍 In the real worldPart 5 / 8

Heart disease, and what causes it

Coronary heart disease begins when fatty deposits narrow the coronary arteries that supply the heart muscle itself. Less blood means less oxygen; a complete blockage causes a heart attack.

Risk factors are largely modifiable: a diet high in saturated fat, smoking, lack of exercise, obesity and high blood pressure. South Asian populations have a notably higher genetic risk, which makes the modifiable factors matter more, not less.

Treatments range from stents that hold an artery open, to bypass surgery using a vessel from elsewhere in the body.

Exercise strengthens the heart muscle, so it pumps more blood per beat and the resting pulse falls, which is why a trained athlete has a low resting heart rate.

6⚠️ Common mistakesPart 6 / 8

Where marks get lost

  • "Arteries carry oxygenated blood." Usually, but the pulmonary artery does not. Define by direction.
  • Saying the heart is on the left. It is roughly central, tilted left.
  • Left/right confusion on diagrams. They are labelled from the patient's view, so the right atrium appears on your left.
  • "Red blood cells have no nucleus because they are dead." They lose it to carry more haemoglobin.
  • Forgetting valves are in veins, not arteries.
7✅ SummaryPart 7 / 8

What to remember

  • Double circulation: through the heart twice per circuit.
  • Right side → lungs · left side → body · left ventricle thickest.
  • Arteries away, veins towards; veins have valves.
  • Capillaries are one cell thick for exchange.
  • Haemoglobin + oxygen ⇌ oxyhaemoglobin.
8✏️ Worked examplePart 8 / 8

Watch one worked through

Here is one done slowly, with the reason for every move. Then one for you.

Watch one first

Explain why the wall of the left ventricle is much thicker than the wall of the right ventricle.

  1. Say where each one pumps blood to.
    right ventricle → lungs left ventricle → whole body
    Always start a structure question by naming the job. The difference in structure follows from the difference in job.
  2. Compare the distances involved.
    lungs: short trip body: head to toes
    Distance means resistance. Blood has to be pushed through far more vessel to reach a foot than to reach a lung.
  3. More distance needs more pressure, and pressure comes from muscle.
    more pressure → more muscle → thicker wall
    The chain from job to pressure to muscle to thickness is the answer. Stating only the first and last loses the middle marks.
  4. Note why the right one must stay thin.
    lung capillaries are delicate too much pressure → damage
    It is not that the right ventricle is weak. A thicker right wall would burst the lungs, so thin is correct for its job.

Answer: The left ventricle pumps blood around the whole body, which needs much higher pressure and therefore more muscle; the right only pumps to the nearby lungs, whose delicate capillaries would be damaged by high pressure

Now you try

Which vessel carries blood from the heart to the lungs? Two words.

Show the answer

pulmonary artery

Practise Transport in Humans

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🧠 5 quizzes on Transport in Humans (2 easy, 2 medium, 1 hard)

Work up from easy to hard: the hard quiz asks the Class 10 exam-style questions on Transport in Humans.

🖨️ Printable worksheet

Transport in Humans on paper for Class 10, with room to write the working out. Preview the first page free.

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