Kidney Blood Supply
Renal Arteries, Arterioles, Capillaries, and Veins
Introduction
The renal blood supply comprises a complex network of arteries, arterioles, capillaries, and veins that enables the kidneys to filter blood and maintain homeostasis.
Blood enters the kidney through a large renal artery, which branches into smaller arteries as it flows toward the renal cortex.
Within the cortex, these arteries penetrate the renal lobes and divide into arterioles. These arterioles lead to the glomerular capillaries, where blood filtration occurs.
After filtration, blood flows through a network of capillaries that allow substances to be exchanged with nearby kidney tubules.
Finally, smaller veins collect blood from the capillaries. These veins converge to form larger veins that transport the blood away from the renal lobes and cortex. They drain into the renal vein, which returns the filtered blood to the systemic circulation.
Major Arteries
Renal Artery
The kidneys receive blood from the renal arteries, which branch perpendicularly from the descending (abdominal) aorta. These arteries provide the kidney with an ample blood supply, amounting to approximately 20% to 25% of the heart’s output, or about 1 liter of blood per minute.
Segmental Arteries
Just after the renal artery enters the renal hilum, it branches into segmental arteries, which supply blood to the five segments or regions of the kidney.
Interlobar Arteries
The segmental arteries divide into interlobar arteries, which pass through the renal columns to supply the renal lobes.
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Blood is directed towards the renal lobes because they contain the nephron tubules that form urine. A kidney usually has 7 to 9 renal lobes, each consisting of two regions. The lighter outer region is part of the renal cortex, and the darker inner region, the renal pyramid, is part of the renal medulla.
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Small Arteries
Arcuate Arteries
The arcuate arteries branch from the interlobar arteries and enter the renal lobes, where they run alongside the arched intersections between the renal cortex and renal medulla.
Cortical Radiate Arteries
Cortical radiate arteries (interlobular arteries) branch at right angles from the arcuate arteries and extend into the renal cortex.
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Arterioles and Glomerulus
Afferent Arterioles
The cortical radiate arteries give off afferent arterioles that deliver blood to the Bowman’s capsules of nephrons.
Glomerulus
Within a Bowman’s capsule, an afferent arteriole forms a tuft of high-pressure capillaries called the glomerulus. The glomerulus and the Bowman’s capsule together form the renal corpuscle. Blood is filtered across the capillary walls of this tuft through the glomerular filtration barrier, which yields its filtrate of water and soluble substances to the interior space of the Bowman’s capsule.
Efferent Arterioles
The glomerular capillaries eventually merge to form an efferent arteriole, which exits the Bowman’s capsule.
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Capillaries Near Nephron Tubules
The efferent arterioles branch extensively, forming a network of capillaries that wind around the renal tubules of the nephrons. The proximity of the capillaries and renal tubules allows the exchange of substances between the neighboring structures.
Peritubular Capillaries
The capillaries that travel alongside the proximal and distal convoluted tubules of the nephrons are called the peritubular capillaries.
Vasa Recta Capillaries
Those that travel alongside the loops of Henle of the juxtamedullary nephrons are called the vasa recta capillaries.
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Veins
Cortical Radiate Veins
After the blood is cleansed and rebalanced by the nephrons and nearby capillaries, it drains into the cortical radiate veins, also known as the interlobular veins.
Arcuate Veins
The cortical radiate veins merge at right angles with the arcuate veins, which carry the blood away from the renal lobes.
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Interlobar Veins
The blood from the arcuate veins flows into the interlobar veins and then along the edges of the renal columns.
Renal Vein
Blood is then carried away from the kidney by the renal vein and delivered to the inferior vena cava, which transports it to the heart.
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Assessment
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References and Attributions
Cleveland Clinic – “Renal Artery.”
ScienceDirect – “Kidney Blood Flow.”
ScienceDirect – “Kidney Circulation.”
OpenStax; Anatomy and Physiology – “Gross Anatomy of the Kidney” (Access for free at – https://openstax.org/books/anatomy-and-physiology/pages/1-introduction).
Radiopaedia – “Kidneys.”
University of Nottingham – “Anatomy of the Kidneys: Blood Flow“.