---
title: "Heart Structure & Double Circulation"
description: "Describe the structure of the heart (four chambers, valves, coronary arteries) and explain how it pumps deoxygenated blood to the lungs and oxygenated blood to the body in a double circulatory system"
canonical: https://lightmysky.com/learn/science/heart-structure-and-double-circulation-mt_TR2oTy9c2M
source: https://lightmysky.com/learn/science/heart-structure-and-double-circulation-mt_TR2oTy9c2M.md
retrieved: 2026-10-19
---

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# Heart Structure & Double Circulation

Describe the structure of the heart (four chambers, valves, coronary arteries) and explain how it pumps deoxygenated blood to the lungs and oxygenated blood to the body in a double circulatory system

Subject: Science · Area: Organisms & Life Processes · Ages 12 to 13
Page: https://lightmysky.com/learn/science/heart-structure-and-double-circulation-mt_TR2oTy9c2M

## Ready when they can

- Labels a diagram of the heart showing atria, ventricles, valves, aorta, vena cava, and pulmonary vessels
- Traces the route of blood through the double circulatory system
- Explains the role of valves in preventing backflow
- Compares arteries, veins, and capillaries

## Lesson: Heart Structure & Double Circulation

Your heart is really two pumps joined side by side, a right pump and a left pump. Each side has two chambers: an atrium on top that receives blood, and a ventricle below that pumps blood out. A thick wall called the septum keeps the two sides separate, so blood on the right never mixes with blood on the left.

*(drawing: Blood low in oxygen enters the right atrium through the vena cava, drops into the right ventricle, and gets pumped to the lungs.)*

*(drawing: Blood full of oxygen comes back from the lungs into the left atrium, drops into the left ventricle, and gets pumped out through the aorta to the whole body.)*

**Tip.** Valves sit between each atrium and ventricle, and where blood leaves the ventricles. They work like one-way doors: blood pushes through, then the valve snaps shut so it cannot slosh backward when the heart squeezes.

**Example.** Even the heart muscle needs its own blood supply. Coronary arteries branch off the aorta and wrap around the heart, feeding the muscle that never gets to rest. Arteries like these have thick, muscular walls built for high pressure. Veins carry blood back at low pressure and have their own valves to stop it sinking backward. Capillaries are the thinnest vessels of all, so thin that oxygen and nutrients can pass straight through into cells.

**Recap.** The heart is two pumps in one: the right side sends blood to the lungs, the left side sends blood to the body, and valves make sure it only ever flows one way.

## Practice

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

## Needs first

- [The Circulatory System](https://lightmysky.com/learn/science/the-circulatory-system-mt_BX4D8cCFtQ)
- [Gas Exchange & Breathing](https://lightmysky.com/learn/science/gas-exchange-and-breathing-mt_V9SQS9gLFw)
- [Nutrient Transport in Animals](https://lightmysky.com/learn/science/nutrient-transport-in-animals-mt_YSyjTZfjvv)

## Opens up

- [Blood Components and Blood Vessels](https://lightmysky.com/learn/science/blood-components-and-blood-vessels-mt_aWZ2sGXGMn)