Grade 8 · Science · 2 minutes
How your heart moves your blood
Two pumps, two loops, one-way valves.
Key terms
- Atria
- The two upper chambers of the heart, which collect blood as it comes in.
- Ventricles
- The two lower chambers of the heart, which squeeze blood out.
- Double circulation
- Blood making two loops, one through the lungs and one through the body, both passing through the heart.
- Capillaries
- Tiny blood vessels so thin that blood cells squeeze through in single file, handing oxygen to cells.
- Valves
- Flaps in the heart that open to let blood through and snap shut to stop it flowing backward.
- Arteries and veins
- Arteries carry blood away from the heart, and veins carry blood back to it.
Transcript
Put your hand on your chest. That thump is your heart, and it beats about a hundred thousand times every single day. So where is all that blood going?
Your heart is really two pumps, side by side. It has four chambers. The two on top, called atria, collect blood as it comes in. The two on the bottom, called ventricles, squeeze it out.
The right side pumps blood that's low in oxygen up to your lungs. There, it drops off carbon dioxide, and picks up fresh oxygen.
That blood, now rich in oxygen, flows back to the left side, the stronger pump. It pushes blood out to your whole body, and then back to the right side again. Two loops, one heart. That's double circulation.
Blood travels through three kinds of blood vessels. Arteries carry blood away from the heart. Veins carry it back. And in between are capillaries, so thin that blood cells squeeze through in single file, handing oxygen to your cells.
So what stops blood from flowing backward? Valves. These flaps swing open to let blood through, then snap shut behind it. That snapping shut is the lub dub sound of your heartbeat.
At rest, an adult's heart beats about sixty to a hundred times a minute. But when you exercise, your muscles need more oxygen, fast. So your heart beats faster and harder, to deliver it.
So, your heart is two pumps with four chambers. The right side sends blood to the lungs, and the left side sends it to the body. And valves keep it all flowing in one direction.
Sources
Every fact in the video, and where it comes from.
- 1health.clevelandclinic.org/facts-about-the-heart
- The heart beats about 100,000 times a day.
- 2webarchive.library.unt.edu/eot2008/20080916154956/http:/www.nhlbi.nih.gov…
- The heart has four chambers: two atria (upper, receive blood) and two ventricles (lower, pump blood out).
- 3webarchive.library.unt.edu/eot2008/20080922155727/http:/www.nhlbi.nih.gov…
- The heart has two sides separated by the septum: the right side pumps blood to the lungs to pick up oxygen; oxygen-rich blood returns to the left side, which pumps it to the body.
- Four valves (tricuspid, pulmonary, mitral, aortic) open to let blood through and shut to stop it flowing backward.
- 4thenational.academy/teachers/programmes/biology-secondary-ks4-high…
- Blood passes through the lungs (pulmonary loop) for gas exchange before circulating around the body (systemic loop): a double circulatory system.
- 5my.clevelandclinic.org/health/body/21704-heart
- The left ventricle is the strongest chamber; it pumps blood out to the whole body.
- 6academickids.com/guides/blood-vessels-for-kids
- Arteries carry blood away from the heart; veins carry blood back to the heart; capillaries are the smallest vessels, connecting them, where oxygen moves into cells and carbon dioxide moves into the blood. Red blood cells pass through capillaries in single file.
- 7med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and…
- The 'lub-dub' heart sounds are made by valves closing (lub: AV valves; dub: aortic and pulmonary valves), not by the muscle contracting.
- 8mayoclinic.org/healthy-lifestyle/fitness/expert-answers/heart…
- A normal resting heart rate for adults is 60 to 100 beats per minute.
- 9heart.org/en/healthy-living/fitness/fitness-basics/targe…
- During exercise working muscles need more oxygen, so the heart beats faster and pumps more blood per beat.
Image and sound credits
- Diagrams drawn in code (no stock images)
- Heartbeat sound synthesised in code
- Music: generated with ACE-Step
- Voice: Gemini TTS
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