원문 - 영어 - how the heart works

How the heart works

Today, we talk about the object of his work. The heart is a complex organ that starts beating a few weeks after conception. At this point the heart is a tube. In the coming days, it grows and bends into the shape or the heart.

Later, it divides into four parts. As the heart beats, it pumps blood through these chambers and the blood vessels in the body. The body is estimated to have at least ninety six thousand kilometers of bloods vessels.