We just learned about the pulmonary valve in the heart that opens for blood to go to the lungs for oxygen.
The walls of the heart are made up of different types of layers.
The inside wall of the heart is called the endocardium.
This is a thin layer that keeps the inside of the heart soft, smooth and wet, and also helps the heart send it's electrical signals all over that are part of what keeps it beating at the right time.
(from: wikipedia - endocardium)
Kid Facts - Blast from the past: Internal Thoracic Artery
