11 Surprising Facts About the Respiratory System

Pulmonary circulation is the process by which blood travels from the heart to the lungs and then back to the heart. This flow keeps the heart supplied with oxygen, which the blood picks up from the lungs.

In 1243, the Arab physician Ibn al-Nafis became the first person to describe this complicated process, when he detailed it in his work, "Commentary on Anatomy in Avicenna's Canon."It wasn't until 300 years later that European scholars came to the same conclusion, according to a 2008 article in the Journal of Applied Physiology.