Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want transport in mammals — heart structure, blood vessels and double circulation — to become reliable marks instead of a confused left-right diagram.
What query it owns: how to understand and revise transport in mammals in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the transport-in-mammals revision-guide angle, while Tutopiya’s Transport In Mammals subtopic page owns the learning resource and the free Transport In Mammals quiz owns the practice.

Transport in mammals uses the heart and blood vessels to carry oxygen, nutrients, hormones and waste around the body. Cambridge IGCSE Coordinated Science (0654) tests whether you can label the heart, trace blood flow through double circulation, and compare arteries, veins and capillaries. This guide covers the syllabus structures, the blood-flow sequence, and the question types that appear every year.

Key takeaways

• Mammals have double circulation — blood passes through the heart twice per complete circuit.
• The heart has four chambers; the left ventricle has the thickest wall.
• Arteries carry blood away from the heart; veins return blood to the heart; capillaries exchange materials with tissues.
• Valves prevent backflow — bicuspid, tricuspid and semilunar valves.
• Exam answers must trace blood flow with named vessels and oxygenation state.

What is transport in mammals in Cambridge IGCSE Coordinated Science?

The mammalian circulatory system is a closed double circulation. The right side of the heart pumps deoxygenated blood to the lungs; the left side pumps oxygenated blood to the rest of the body. Blood, tissue fluid and lymph transport substances; red blood cells carry oxygen, plasma carries dissolved substances, and white blood cells fight infection.

You can read the full explanation, labelled diagrams and notes on Tutopiya’s Transport In Mammals subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Double circulation	Heart → lungs → heart → body	”Explain what is meant by double circulation”
Four chambers	RA, RV, LA, LV	Label and function questions
Blood vessels	Artery, vein, capillary roles	”Compare arteries and veins”
Valves	Prevent backflow	”State the function of heart valves”
Blood components	RBC, WBC, platelets, plasma	”State the function of red blood cells”

Blood flow through the heart — step by step

The safest method works for every trace-the-blood-flow question.

1. Identify the starting point — usually body tissues (deoxygenated) or lungs (oxygenated).
2. Deoxygenated blood enters the right atrium from the vena cava.
3. Blood passes through the tricuspid valve into the right ventricle.
4. Right ventricle contracts → blood through semilunar valve into pulmonary artery → lungs.
5. Oxygenated blood returns via pulmonary vein to the left atrium.
6. Blood passes through bicuspid (mitral) valve into the left ventricle.
7. Left ventricle contracts → blood through semilunar valve into aorta → body.

Once you have traced the route a few times, test yourself with the free Transport In Mammals quiz — it tells you fast whether the sequence has actually stuck.

Arteries vs veins vs capillaries

Vessel	Direction	Wall	Lumen	Valves
Artery	Away from heart	Thick, muscular, elastic	Narrow	No
Vein	Towards heart	Thinner walls	Wide	Yes (prevent backflow)
Capillary	Links artery to vein	One cell thick	Very narrow	No

Transport in mammals in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical transport stem
Name	Identify structure or vessel	”Name the blood vessel that carries blood to the lungs.”
Describe	Sequence or structure	”Describe the route of blood through the heart.”
Explain	Cause and effect	”Explain why the left ventricle has a thicker wall.”
Compare	Similarities and differences	”Compare arteries and veins.”
State	Short factual answer	”State the function of capillaries.”

Worked exam-style stems (how to answer the wording)

1. “Name the blood vessel that carries oxygenated blood from the lungs to the heart.” Pulmonary vein. Mark-scheme reward: pulmonary vein (not pulmonary artery).
2. “Explain why the left ventricle has a thicker muscular wall than the right ventricle.” The left ventricle pumps blood to the whole body at high pressure; the right ventricle only pumps to the nearby lungs. Reward: distance/pressure link.
3. “Compare arteries and veins.” Arteries carry blood away from the heart, have thick muscular walls and no valves; veins carry blood to the heart, have thinner walls and valves to prevent backflow. Reward: direction + wall + valves.

When you can recognise the wording instantly, work the full set on the Transport In Mammals quiz to lock the blood-flow route in.

How transport in mammals connects to the rest of the syllabus

Transport links to Gas Exchange (oxygen uptake at lungs) and Respiration (oxygen use in cells). Compare with Transport In Plants. The Cambridge IGCSE Coordinated Science resource hub links every Transport subtopic.

Common mistakes students make

• Confusing pulmonary artery (to lungs, deoxygenated) with pulmonary vein (from lungs, oxygenated).
• Saying arteries always carry oxygenated blood (pulmonary artery carries deoxygenated blood).
• Forgetting valves prevent backflow in the heart and veins.
• Mixing up left and right sides of the heart on diagrams.
• Ignoring capillaries as the site of exchange with tissues.

When you need more support

If transport in mammals questions keep tripping you up — especially blood-flow traces — work through the Transport In Mammals quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is transport in mammals hard in Cambridge IGCSE Coordinated Science? The structures are logical once you learn the blood-flow sequence, but marks are lost when students confuse vessel names and oxygenation state.

What is double circulation? Blood passes through the heart twice in one complete circuit — once to the lungs and once to the body.

Why does the left ventricle have a thicker wall? It pumps blood to the entire body at high pressure, unlike the right ventricle which only pumps to the lungs.

How do I revise transport in mammals effectively? Trace blood flow step by step on a diagram, compare blood vessel types, then take the Transport In Mammals quiz.

Ready to master Cambridge IGCSE Coordinated Science transport in mammals?

Start with the Transport In Mammals subtopic page, then book a free trial with a Cambridge IGCSE Coordinated Science specialist to turn transport in mammals into guaranteed marks.

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