Ibn al-Nafis (Ala al-Din al-Qurashi)

Ala al-Din Ibn al-Nafis (1213–1288 CE), born in Damascus, studied at the famous Bimaristan al-Nuri before moving to Cairo, where he served as chief physician to Sultan Baibars and head of the prestigious Al-Mansuri Hospital. In his 1242 treatise Commentary on Anatomy in Avicenna's Canon, he made one of the greatest anatomical discoveries in medical history.

Directly refuting Galen's 1,000-year dogma that blood passes through invisible pores in the cardiac ventricular septum, Ibn al-Nafis proved that the septum is solid and non-porous. He demonstrated that venous blood must flow from the right ventricle of the heart through the pulmonary artery to the lungs, where it mingles with air, before returning via the pulmonary vein to the left ventricle.