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usmledoc

hi,
i am new to this forum.just started studying for usmle step1.am doing physiology.i had a question.cud anyone please explain this to me.

as we go away from the heart into the systemic arteries,the sysytolic pressure increases and distolic pressure falls.systolic pressure increases becos the vessels become less compliant as compared to aorta,but why does the diastolic pressure fall?
alsoin peripheral circulation section in kaplan notes[physio]they say that a "decrease in compliance" will increase pulse press since sys increases[which is understandable]and diastolic decreases.please explain the latter part.
thanx

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As you know that compliance =volume /pressure.In the arterial system, the aorta has the highest compliance, due in part to a relatively greater proportion of elastin fibers versus smooth muscle and collagen. This serves the important function of dampening the pulsatile output of the left ventricle, thereby reducing the pulse pressure. If the aorta were a rigid tube, the pulse pressure would be very high. Because the aorta is compliant, as blood is ejected into the aorta, the walls of the aorta expand to accommodate the increase in blood volume contained within the aorta. The more compliant the aorta, the smaller the pressure change during ventricular ejection (i.e., smaller pulse pressure).AS WE GO AWAY FROM AORTA THE SYSTEM BECOMES LESS AND LESS COMPLIANT.....HOPE THIAS HELPS.

BR

diastolic pressure is the pressure due to ventricles being refilled by blood.and obviously this pressure is ought to fade as you go away.. hope I answered your q.