Cambridge IGCSE Biology (0610) · Transport in animals
Mini-Lesson
Transport in animals
This mini-lesson walks you through Cambridge IGCSE Transport in animals: the circulatory system, the structure of the heart, the three blood vessels (artery, vein, capillary), the components of blood, and the double circulation.
Work through each screen, answer the questions as you go (some wordy, some calculations) and collect ⭐ stars. Watch for the Key term flags. Press Start when you're ready.
Transport · the circulatory system
The circulatory system & double circulation
Mammals have a double circulation — blood passes through the heart twice for each complete trip around the body. There are two separate loops:
Pulmonary circulation — heart → lungs → heart. Here blood picks up oxygen and drops off carbon dioxide.
Systemic circulation — heart → rest of the body → heart. Here oxygen is delivered to the tissues.
Double circulation gives blood a high pressure again after the lungs, so it reaches the body faster.
Why double? After the lungs, blood pressure is low. Returning to the heart lets it be pumped out again at high pressure, so oxygen reaches body cells quickly and efficiently.
Transport · the heart
The heart
The heart is a muscular pump with four chambers: two atria (top) and two ventricles (bottom). The right side handles deoxygenated blood; the left side handles oxygenated blood — the two are kept apart by the septum.
The left ventricle has the thickest wall — it pumps blood at high pressure all around the body.
Atria receive blood; ventricles pump it out.
Valves stop backflow so blood only flows one way.
The left ventricle wall is thicker than the right because it pumps to the whole body; the right only pumps to the nearby lungs.
Quick check
Why the thick wall?
?The left ventricle has a much thicker muscular wall than the right ventricle. What best explains why?
Transport · blood vessels
Arteries, veins & capillaries
There are three types of blood vessel, each suited to its job:
Arteries carry blood away from the heart at high pressure. They have thick, elastic, muscular walls and a small lumen. (All carry oxygenated blood except the pulmonary artery.)
Veins carry blood back to the heart at low pressure. They have thin walls, a large lumen and valves to stop backflow. (All carry deoxygenated blood except the pulmonary vein.)
Capillaries are one cell thick, so substances (oxygen, glucose, CO₂) can diffuse quickly between blood and cells.
Exam trap: arteries carry blood away (A for Away), veins carry it back. Direction is defined by the heart, not by whether the blood is oxygenated.
Sort it
Which vessel?
Tap a feature, then tap the vessel it belongs to. (Some are shared by all.)
🔁 All vessels
🔴 Artery
🔵 Vein
Transport · the blood
The components of blood
Blood is made of a liquid called plasma carrying three kinds of cell/fragment:
Red blood cells — carry oxygen using the red pigment haemoglobin. They have no nucleus and a biconcave shape (more room + surface area for oxygen).
White blood cells — part of the immune system; some engulf pathogens (phagocytes), others make antibodies (lymphocytes).
Platelets — cell fragments that help blood clot at wounds.
Plasma — the straw-coloured liquid that transports CO₂, digested food, urea, hormones and heat.
Quick check
What carries oxygen?
?Which component of the blood carries oxygen, and what makes it well adapted for the job?
Calculate
Your turn — heart rate
1A heart beats 18 times in 15 seconds. Calculate the heart rate in beats per minute.