---
title: "Heart & Blood Circulation"
description: "Describe the circulatory system in detail: the heart has four chambers (two atria, two ventricles) that pump blood in a double loop — one to the lungs for oxygen and one to the rest of the body to del"
canonical: https://lightmysky.com/learn/science/heart-and-blood-circulation-mt_g_M4Vh_pK7
source: https://lightmysky.com/learn/science/heart-and-blood-circulation-mt_g_M4Vh_pK7.md
retrieved: 2026-10-19
---

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# Heart & Blood Circulation

Describe the circulatory system in detail: the heart has four chambers (two atria, two ventricles) that pump blood in a double loop — one to the lungs for oxygen and one to the rest of the body to deliver it — through arteries, veins, and tiny capillaries

Subject: Science · Area: The Human Body · Ages 9 to 11
Page: https://lightmysky.com/learn/science/heart-and-blood-circulation-mt_g_M4Vh_pK7

## Ready when they can

- Name the four heart chambers and describe the double-loop pathway (heart → lungs → heart → body)
- Distinguish arteries (carry blood away from heart), veins (carry blood back to heart), and capillaries (tiny vessels where exchange happens)
- Name the components of blood: red blood cells (carry oxygen), white blood cells (fight infection), platelets (help clotting), plasma (liquid)

## Lesson: The Heart's Double Loop

Put your hand on your chest and feel your heartbeat. That beat comes from two pumps working side by side. Each side has two chambers: an atrium on top and a ventricle below it. That makes four chambers in all: right atrium, right ventricle, left atrium, and left ventricle.

*(drawing: Blood leaves the heart, picks up oxygen in the lungs, comes back to the heart, then heads out to the body.)*

Blood travels through three kinds of vessels. Arteries carry blood away from the heart. Veins carry blood back to the heart. Capillaries are the tiniest vessels, so thin that oxygen and nutrients can pass right through their walls into your cells.

Blood has four parts. Red cells carry oxygen. White cells fight germs. Platelets help blood clot at a cut. Plasma is the liquid that carries them all.

**Example.** Follow one drop of blood. It leaves the right side of the heart and travels to the lungs, where it picks up fresh oxygen. It flows back into the left side of the heart, then gets pumped out through arteries to your muscles and organs. There, capillaries let the oxygen slip into your cells, and the drop heads home through veins to start again.

**Tip.** Think A for arteries and away. Arteries carry blood away from the heart. Veins carry it back.

**Recap.** Blood makes two loops through the heart's four chambers: one to the lungs and back, one to the body and back, through arteries, veins, and capillaries.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Cells, Tissues & Organs](https://lightmysky.com/learn/science/cells-tissues-and-organs-mt_C7FNeIDGc6)
- [The Heart & Blood](https://lightmysky.com/learn/science/the-heart-and-blood-mt_lp1eTsQen7)

## Opens up

- [The Circulatory System](https://lightmysky.com/learn/science/the-circulatory-system-mt_BX4D8cCFtQ)
- [Circulation & Breathing Together](https://lightmysky.com/learn/science/circulation-and-breathing-together-mt_QK-ZZb7UUN)