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Heart Lesson for Kids

Instructor: Rachel Torrens
In this lesson, we'll discuss the heart, that small but mighty muscle that pushes blood through your body. You'll explore the structure of the heart, including its main parts, and you'll learn why blood flows in one direction through the heart.

Heart Structure

Your heart is small, but it's a hard worker. It is about the size of your fist and beats roughly 2.5 billion times in a lifetime. It's also made up several smaller parts that work together to pump blood. The main parts of the heart are the chambers and valves, which we will discuss below.

Chambers: Atria and Ventricles

Close your eyes, and picture yourself standing in your bedroom. Now imagine walking to the bathroom. Did you go through another room or any doors?

Believe it or not, your heart is composed of parts much like the rooms and doors in your home. The heart has four chambers, which are like rooms, with two chambers sitting atop the other two. The upper chambers are known as the atria, and the bottom chambers are known as the ventricles. The atria and ventricles sit next to each other, and so there's a right atrium and ventricle as well as a left atrium and ventricle.

The heart has two atria and two ventricles separated by valves.
Diagram of the heart

Valves

The chambers are separated by valves. Like the doors in your home, valves open and close, controlling the flow of blood from one chamber to another and to the rest of the body. When a real door closes, it makes a 'thud.' Likewise, when valves open and close, they make a noise, similar to 'lub-DUB.' So, the sound of your heartbeat is really the sound of your valves opening and closing.

Also like most real doors in your home, heart valves only open in one direction. These one-way valves help to direct the flow of blood. So let's look more closely at the exact pathway the blood takes through the heart.

Heart Function and One-Way Blood Flow

In order to understand the pathway of blood, you need to know that blood has two forms: oxygen-poor and oxygen-rich. Part of blood's purpose in traveling through your body is to deliver oxygen to your tissues, and for this reason, the oxygen-poor blood must be turned into oxygen-rich blood.

So, oxygen-poor blood from the body flows into the right atrium. The blood passes through a valve into the right ventricle. The right ventricle pumps the blood through another valve to the lungs. Just like stopping to refuel the car on a road trip, your blood swings by the lungs to pick up oxygen.

Blood flows in one direction through the heart.
Flow of blood through the heart diagram.

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