Your heart has four rooms. Atrial cells make up the walls of the two top rooms, and they give the blood a push down into the big rooms below.
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Your heart has two small top rooms called the atria (AY-tree-uh). One of them is called an atrium. Their walls are made of atrial cells.
Atrial cells are a kind of heart muscle cell. They are shaped like short, branching logs with stripes. Their ends hook onto the next cells with special joins, so a heartbeat signal can pass from cell to cell.
Scroll up to the 3D model and press Beat! to see the cells squeeze together.
Blood coming back to your heart fills the top rooms first. Then atrial cells squeeze and push the blood down into the two big bottom rooms. Those big rooms then pump it out to your body and lungs.
Atrial cells have a second job too. When too much blood stretches the top rooms, they let out a messenger chemical. It tells your kidneys to get rid of some extra salt and water.
That messenger chemical is a hormone. So your heart is not only a pump. It sends hormone messages too!
By Peekaboo Kidz. A fun video for kids.
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