Atrium (heart) facts for kids

Quick facts for kids Atrium
Front view of heart showing the atria
Latin	Atrium

The atrium (say: AY-tree-um) is an important part of your heart. It's like an entry room or a waiting room for blood. Your heart has two atria (that's the plural of atrium). They are the upper chambers of the heart.

The atria collect blood before it moves into the lower chambers, called ventricles.

How Atria Work

Your heart works like a pump, and the atria are a key part of this action.

Receiving Blood

• When your atria are relaxed, they fill up with blood. This relaxed phase is called diastole.
• The right atrium receives blood that has traveled all over your body. This blood is low in oxygen. It comes back to the heart through large veins called vena cavae.
• The left atrium receives blood that has just come from your lungs. This blood is rich in oxygen and ready to be pumped to the rest of your body.

Pumping Blood

• Once the atria are full, they squeeze or contract. This squeezing phase is called systole.
• When the atria contract, they push the blood down into the ventricles, which are the next chambers in the heart.
• From the ventricles, the blood is then pumped out to either the lungs or the rest of the body.

Atria in Animals

Many animals have a closed circulatory system, just like humans. This means their blood stays inside blood vessels. Most of these animals have at least one atrium in their heart. Humans, and many other animals, have two atria.

Images for kids

• 

  Right heart anatomy

• 

  left atrial appendage shown at upper right

• 

  CT scan of the chest showing a thrombus in the left atrial appendage (left: axial plane, right: coronal plane)

See also

In Spanish: Aurícula (corazón) para niños