History of the Human Body
Doctors have been trying to figure out how the human body works since the Stone Age, and there are still many things we don't know about the human body even today. Medical researchers all over the world have contributed bits of knowledge, and learned from one another. Some things they figured out were right; other times their ideas turned out to be wrong.
In Ancient Egypt, about 2000 BC, doctors knew that people had a stomach, a small intestine, a large intestine, an appendix, a liver, a spleen, two kidneys, and a bladder. They knew women had a uterus, and that babies grew there. Egyptian doctors figured out that your pulse was related to your heartbeat, though they didn't know exactly why. They knew that your heart was connected to your arteries (blood vessels). They knew that your bronchial tubes connected your throat to your lungs.
Egyptian doctors thought that air came in through your mouth and went to your lungs and your heart, and from there the air went through your arteries all over your body. That's right as far as it goes. But they - like Chinese, Indian, American and Australian doctors at the same time - thought that a lot of illnesses were caused by demons.