Bio HW

Egyptions

15,000 BCE

The earliest known writings on the circulatory system are found in the Ebers Papyrus by the Egyptions. In the papyrus, it acknowledges the connection of the heart to the arteries. The Egyptians thought air came in through the mouth and into the lungs and heart. From the heart, the air travelled to every part of the body through the arteries.

Ancient India

6000 BCE

The knowledge of circulation of vital fluids through the body was known to the Ayurveda physician Sushruta in ancient India. He also seems to have possessed knowledge of the arteries, described as 'channels'.

Hippocrates

4000 BCE

The valves of the heart were discovered by a physician of the Hippocratean school. However their function was not properly understood then. Because blood pools in the veins after death, arteries look empty. Ancient anatomists assumed they were filled with air and that they were for transport of air.

Greece

2000 BCE

Greek anatomist Erasistratus observed that arteries that were cut during life bleed. He ascribed the fact to the phenomenon that air escaping from an artery is replaced with blood that entered by very small vessels between veins and arteries.

Galen

2

The Greek physician Galen knew that blood vessels carried blood and identified venous (dark red) and arterial (brighter and thinner) blood, each with distinct and separate functions. Growth and energy were derived from venous, while arterial blood gave vitality by containing pneuma (air) and originated in the heart. Blood flowed from both creating organs to all parts of the body where it was consumed and there was no return of blood to the heart or liver.

Avicenna

Sep 26, 1025

Persian physician, Avicenna, accepted the Greek notion regarding the existence of a hole through which the blood traveled between the ventricles. Despite this, Avicenna correctly provided the first explanation of pulsation: "Every beat of the pulse comprises two movements and two pauses. Thus, expansion : pause : contraction : pause. The pulse is a movement in the heart and arteries ... which takes the form of alternate expansion and contraction."

Ibn al-Nafis

Sep 26, 1242

Arabian physician, Ibn al-Nafis, became the first person to accurately describe the process of pulmonary circulation stateing that "the blood from the right chamber of the heart must arrive at the left chamber but there is no direct pathway between them. The thick septum of the heart is not perforated and does not have visible pores as some people thought or invisible pores as Galen thought."

Leonardo da Vinci

Sep 26, 1490

Leonardo made a number of advances in the understanding of blood flow and showed that the heart is indeed a muscle and that it does not warm the blood (a common belief at the time), found it has four chambers, connected the pulse in the wrist with contraction of the left ventricle, deduced that currents in the blood flow that were created by structures in the main aorta artery help heart valves to close and suggested that arteries "fur" up over a lifetime, creating a health risk.

William Harvey

Sep 26, 1628

William Harvey, performed a sequence of experiments, which showed that there had to be a direct connection between the venous and arterial systems throughout the body, and not just the lungs. Most importantly, he argued that the beat of the heart produced a continuous circulation of blood through minute connections at the extremities of the body. This is a conceptual leap that was quite different from Ibn al-Nafis' discription of the anatomy and bloodflow in the heart and lungs."