Ans. a. Diastolic blood pressure Aerial hypeension is the result of abnormal flow/resistance relationships. Resistance to outflow consists of different components: the systolic component is the one generated by conductance vessels, whereas the diastolic component consists of peripheral resistance, which regulates peripheral blood supply due to the run-off of conductance vessels during left ventricular diastole. Thus, an increase in systemic resistance results in a rise in diastolic blood pressure. If the elasticity of conductance vessels decreases, diastolic run-off also decreases and diastolic blood pressure goes down. When this loss of elasticity occurs, the ejection force cannot be anymore offset by aerial distension, the pulse wave velocity increases and reflex waves to the hea arrive earlier, causing the systolic blood pressure to augment. Such an augmentation, together with decreasing diastolic blood pressure results in an enhancement of the pulse pressure. When the stroke volume is normal, an increase in pulse pressure is, therefore, a marker of altered conductance. However, if, due to loss of elasticity of the conductance aeries diastolic blood pressure goes down, increasing systolic pressure also protects against a decrease in mean pressure. Indeed, in conditions of elevated pulse pressure, the mean pressure can be normal or high, indicating that when evaluating blood pressure all components should be taken into consideration. A high systolic blood pressure associated with a normal mean blood pressure is suggestive of a normal peripheral resistance.'Diastolic PressureSystolic pressure is peak pressure reached during systole, similarly, diastolic pressure refers to lowest pressure during diastole.Diastolic blood pressure is an index to peripheral resistance.Elasticity of aoa and large aeries is mainly responsible for origin and maintenance of diastolic pressure (by Windkessel elastic recoil effect).Because the elasticity is higher in younger subjects, diastolic pressure is maintained and pulse pressure is narrow.Because the elasticity is lower in old persons, diastolic pressure is decreased and pulse pressure is widened.