The Windkessel Effect refers to the waveform shape found in pulsing arterial blood vessels. Translated from German (wind = air, kessel = chamber), this concept was developed by the German physiologist Otto Frank – you may know him from the famous Frank-Starling law of the heart.
This effect occurs due to the interaction between stroke volume and the elastic nature of blood vessels, especially the large arteries. Since these large arteries (e.g. the aorta, common carotid, pulmonary arteries) contain elastin fibers, they distend during systole and recoil during diastole. The Windkessel effect is thus a function of the blood pressure.
Here is a great 3D animation from Anima Res that demonstrates the Windkessel effect beautifully, making it our video of the month: