Blood flow through the kidney

The urinary system plays a major role in maintaining homeostasis by altering the composition, pH, volume, blood pressure, and by producing hormones. Amazingly the Kidneys receive 25% of cardiac output but constitute less than 0.5% of total body mass. The renal artery divides into several segmental arteries within the kidney. Then the segmental arteries divide several times to form interlobar arteries that pass through the renal columns. Arcuate arteries arch between the renal medulla and the cortex at the base of the renal pyramids. Divisions of the arcuate arteries form interlobular arteries which enter the renal cortex and branch off into afferent arterioles. Each afferent arterioles connects to a nephron where it divides to forms a ball shaped capillary network called the glomerulus. These capillaries reunite and form the efferent arterioles that carry the blood out of the glomerulus. The glomerulus is unique because they are located between two arterioles and are considered part of the cardiovascular and urinary system. The efferent arterioles divide to form the peritubular capillaries that surround the tubular parts of the nephron and allow for absorption and reabsorption to and from the blood. There are also long looped shaped capillaries extending from the efferent arterioles called vasa recta that supply tubal portions of the nephron in the renal medulla. The peritubular capillaries merge to form interlobular veins that also receive blood from the vasa recta. The interlobular veins become arcuate veins, then interlobar veins, and finally drain from the kidney through the renal veins.