GCSE · Biology · AQA · Spec 8461

The heart

On every trip round your body, your blood passes through your heart twice. Follow one drop to find out why — and why one 'artery' carries blood low in oxygen.

Follow one drop of blood

Rebuild the route, then break it

4 stages are missing. Use the rest of the loop to work out which goes where.

  1. Stage 1: Vena cava

    The large vein that brings deoxygenated blood back from the body.

  3. Stage 3: Pulmonary artery

    Carries deoxygenated blood to the lungs.

  4. Stage 4: Lungs

    Gas exchange: the blood takes up oxygen and gives up carbon dioxide.

  8. Stage 8: Body organs

    Cells take oxygen from the blood and add carbon dioxide to it, so the blood leaves them deoxygenated.

…and stage 8 leads back to stage 1.

Biology · Anatomy

Inside the heart
rightatriumleftatriumrightventricleleftventricleRIGHT sideLEFT sidevena cavafrom bodypulmonary arteryto lungsaortato bodypulmonary veinfrom lungs

Showing 4 layers: Chambers, Main blood vessels, Coronary arteries, Pacemaker cells

Layers

Explore

tap a part of the heart

Four chambers: two atria on top, two ventricles below. Blue marks deoxygenated blood, on the right side of the heart; red marks oxygenated blood, on the left side. The vena cava and pulmonary vein bring blood in; the pulmonary artery and aorta carry it out.

Drawn as if you are facing the person, so their right side is on your left.

Four vessels

Which vessel does what?

Tick every property each vessel has. Leave a box empty for 'no'. Then check your grid.

Aorta
Vena cava
Pulmonary artery
Pulmonary vein

Where the blood collects oxygen

The lungs: built for gas exchange
the lungsclose-up: alveoli

Showing 2 layers: Lungs and airways, Capillary network

Layers

Explore

tap a part of the lungs

Air travels down the trachea, into the two bronchi, and on through ever-smaller branches to millions of tiny air sacs: the alveoli.

Gas exchange happens here: the blood takes up oxygen and gives up carbon dioxide.

Keeping the beat

What sets the resting heart rate?

At rest, your heart beats at a steady natural rate. Some people's heart rate becomes irregular, and they are fitted with an artificial pacemaker.

Which idea is closest to what you think right now?
How sure are you?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Blood is pumped to the lungs, comes back to the heart, and only then is pumped out to the rest of the body.

What you need to know

  • The heart pumps blood round two loops: the right ventricle to the lungs, the left ventricle to the rest of the body.
  • Five vessels join or serve the heart: vena cava, pulmonary artery, pulmonary vein, aorta and coronary arteries.
  • A group of cells in the right atrium sets the resting heart rate; an artificial pacemaker corrects an irregular rate.
  • Alveoli and their capillary network are adapted for fast gas exchange.

The big picture

The heart pumps blood round a double circulatory system. The right ventricle pumps deoxygenated blood through the pulmonary artery to the lungs for gas exchange; it returns through the pulmonary vein, and the left ventricle pumps it through the aorta to the body, and it returns through the vena cava. The coronary arteries feed the heart muscle itself. A group of cells in the right atrium sets the resting rate, and an artificial pacemaker corrects an irregular one. In the lungs, alveoli and their capillaries are built for fast gas exchange.

Key points

1Double circulatory system: blood passes through the heart twice for every complete circuit of the body.
2Right side: vena cava → right atrium → right ventricle → pulmonary artery → lungs. Left side: pulmonary vein → left atrium → left ventricle → aorta → body.
3Arteries carry blood away from the heart and veins carry it towards the heart — so the pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood.
4The right ventricle pumps blood to the lungs, where gas exchange takes place; the left ventricle pumps blood around the rest of the body.
5Five blood vessels are associated with the heart: the aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries.
6The natural resting heart rate is controlled by a group of cells in the right atrium that act as a pacemaker; artificial pacemakers are electrical devices that correct irregularities in heart rate.
7Gas exchange takes place in the lungs, at the alveoli and the capillary network surrounding them.

Worked example

Problem

The pulmonary artery and the aorta are both arteries. Explain why the pulmonary artery carries deoxygenated blood but the aorta carries oxygenated blood.

⚠ Watch out

Saying the pulmonary artery carries oxygenated blood 'because arteries carry oxygenated blood'. Arteries are defined by direction — they carry blood away from the heart. The pulmonary artery carries deoxygenated blood away from the heart to the lungs, where it will pick up oxygen.

🧠

Memory hook

A for Away: arteries carry blood Away from the heart. The pulmonary artery is going away to collect its oxygen — which is how an artery can carry deoxygenated blood.

✓

Check yourself

Cover the page. Blood has just left the right ventricle. Name the vessel it enters, where it goes, and the chamber it returns to — then say why it must pass through the heart again.

Flashcards

(8)
What does 'double circulatory system' mean?
Blood passes through the heart twice on each complete circuit: the right ventricle pumps it to the lungs, it returns, and the left ventricle pumps it to the rest of the body.
Which two vessels bring blood INTO the heart, and where does each come from?
Vena cava — deoxygenated blood from the body, into the right atrium. Pulmonary vein — oxygenated blood from the lungs, into the left atrium.
The pulmonary artery carries deoxygenated blood. How can an artery do that?
'Artery' means the vessel carries blood away from the heart. The pulmonary artery takes blood away from the heart to the lungs, before it has picked up oxygen there.
Name the five blood vessels associated with the heart.
The aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries.
What controls the natural resting heart rate, and where is it?
A group of cells in the right atrium that act as a pacemaker.
What is an artificial pacemaker?
An electrical device used to correct irregularities in the heart rate.
Which chamber pumps blood through the aorta, and where does that blood go?
The left ventricle; it sends the blood around the rest of the body.
Where in the lungs does gas exchange take place?
At the alveoli, which are surrounded by a network of capillaries.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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