Question

Although they are in different physiological systems, lung residual volume (RV) can perform a function that is akin to the windkessel function of the aorta in the cardiovascular system. It is not the same function as the aorta but it is “along-the-same-lines” or “the same general concept”. Explain what this function is and why it is akin to the windkessel function of the aorta. (2 marks) What other component of total lung volume serves a similar purpose along with the RV? (2 marks)

Answer 1

Windkessel effect of aorta reduces the pulse pressure of the blood in arteries. The difference between systolic and diastolic pressure is pulse pressure. The aorta and big blood vessels have more elastic blood vessels which can take the force of blood entering in to the aorta from left ventricle and store. Because of its elasticity, it can store lot of blood and when heart is in diastole it can continue blood flow to prevent too much pressure changes during the cardiac cycle. That is how blood flow continues even during diastole of cardiac cycle. It maintains the perfusion of organ even during cardiac diastole.

Similarly, residual air that is present in the lungs allows the gas exchange even during exhalation. Residual volume of air also prevents collapse of lungs . Even when we are exhaling also gas exchange is occurring as in the case of aorta which continue to pour blood when heart is in diastole.

Residual volume is the volume of air present in lungs even after forceful exhalation. Expiratory reserve volume also serves the same function. It is the volume of air we exhale when we forcefully breath out after normal inhalation. So the expiratory reserve volume is not exhaled normally. It is in the lungs only. So this volume of air also allows lungs to exchange gases even when we are normally exhaling.