Factors determining blood flow through the kidneys
Although changes in arterial pressure have an effect on blood flow through the kidneys, the kidneys have a mechanism of action to maintain renal blood flow and a fixed glomerular filtration rate.
Renal vascular flow is determined by the renal vascular gradient pressure (hydrostatic pressure differs between the renal artery and vein), dividing the total renal vascular resistance:
(Renal artery pressure - Renal venous pressure) / Total renal vascular resistance.
Renal artery pressure is equal to systemic arterial pressure, and renal venous pressure averages about 3 to 4 mm Hg under normal conditions. Total renal vascular resistance is determined by the total resistance in individual blood vessels, including arteries, arterioles, capillaries, and veins.
Renal artery resistance consists of 3 main segments: the interstitial artery, the artery of arrival, and the aorta. The resistance of these vessels is controlled by the sympathetic nervous system and the local control mechanism inside the kidney is exchanged later. Increasing the resistance of any of the vessels in the kidney leads to a decrease in blood flow through the kidneys.
Board. The pressure and resistance of blood vessels in the circulation of the kidneys are normal
Conversely, a decrease in vascular resistance increases renal flow if arterial and venous pressure remains constant.
Although changes in arterial pressure have an effect on blood flow through the kidneys, the kidneys act to maintain blood flow through the kidneys and glomerular filtration rates are fixed with arterial pressures between 80 and 170 mmHg.