Renal Blood Supply

Blood Supply

The kidney is responsible for cleansing the blood. It does this in a very different way than the liverA large organ that produces bile, detoxifies blood, and stores nutrients.. Therefore, the blood flow into and out of the kidney is important to understand. The heart and lungs do not take blood from the blood they are moving or oxygenating. In contrast, the kidney does take blood. The cellsThe basic structural and functional units of life. in the kidney are consuming glucoseA simple sugar that is the main source of energy for cells. and oxygen for themselves. They are also cleansing that same blood of other items.

Blood exits the left ventricle of the heart. It enters into the aorta and then descends down the abdomen. It branches off to the renal arteryThe artery that supplies blood to the kidney.. The renal artery punctures the kidney at the renal hilum. This is also the place where the ureterThe tube that carries urine from the kidney to the bladder. punctures the kidney.

Arteries

The renal artery enters the kidney and breaks apart into a couple of segmental arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr. It depends on how big your kidney is—if you have seven lobes, you’ll probably have three or four of them. If you have five lobes, you’ll maybe have two of them. It depends, but it’s a segmental arteryLarge arteries that branch from the renal artery and supply blood to different regions of the kidney because it’s going to a segment of the kidney.

Segmental arteries then break off into interlobar arteries. These arteries run between the lobes of the kidney, between the renal pyramids. Interlobar arteries then separate into arcuate arteries.

The word “arcuate” means around. These arteries start to go up into the cortex of the kidney. They bend around the renal pyramids. Arcuate arteries then hook up with cortical radiate arteriesSmall arteries that branch from the arcuate arteries and supply blood to the cortex., which radiate out into the cortex. It’s at this point that the blood from the aorta is subjected to the first capillary bed of the kidney.

Two Capillary Beds

Afferent arteriolesSmall arteries that regulate blood flow into capillaries through vasoconstriction and vasodilation branch off the cortical radiate arteries and lead to the first capillary bed called the glomerulusA network of capillaries in the nephron where blood filtration occurs..  This capillary bed just separates items by size in a process called filtrationThe process by which fluid moves out of capillaries into surrounding tissues due to hydrostatic pre.  We are familiar with filtration from the blood vessels chapter.  Filtration is the process, driven by hydrostatic pressureThe force exerted by a fluid, such as the pressure of blood pushing against the walls of capillaries, that drives waterThe universal solvent essential for life. out of capillariesThe smallest blood vessels where gas, nutrient, and waste exchange occurs between blood and tissues. into interstitial fluidThe fluid surrounding cells within tissues..  Anything left in the glomerulus enters the efferent arterioleThe small artery that carries blood away from the glomerulus after filtration., which drains the glomerulus. 

This is very different than other capillary beds that are drained by venulesSmall veins that collect blood from capillaries and transport it to larger veins..  The glomerulus is drained by an arteriole.  This efferent arteriole leads to a second capillary bed.  Now, this second bed can be called a vasa rectaCapillaries surrounding the loop of Henle in juxtamedullary nephrons that help maintain the medullar. It can also be called a peritubular capillary. The name depends on the type of nephronThe functional unit of the kidney that filters blood and produces urine. that is involved.  This capillary bed is concerned with reabsorptionThe process of fluid moving back into capillaries from surrounding tissues due to colloid osmotic p, a process we also saw in the blood vessels topics.  Reabsorption is driven by the colloid osmotic pressureThe pressure exerted by proteins (mainly albumin) in the blood that pulls water into the capillaries of blood. It sucks fluids back into the venule side of a capillary bed.  This second capillary bed is, in factA statement based on direct observation that is repeatedly confirmed., drained by a cortical radiate venule. This venule connects to the arcuate vein. It then connects to the interlobar veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge and the renal vein. This process carries blood out of the kidney.  There are no segmental veins..

Veins

All the venules that drain the second capillary bed leads to the cortical radiate veins.  Cortical radiate veins are drained by arcuate veins, then interlobar, and then the renal vein.  There are no segmental veins.