Arterial blood enters the kidney through the renal artery, which divides into interlobar arteries (fig. 17.4) that pass between the pyramids through the renal columns. Arcuate arteries branch from the interlobar arteries at the boundary of the cortex and medulla. A number of interlobular arteries radiate from the arcuate arteries into the cortex and subdivide into numerous afferent arterioles (fig. 17.5), which are microscopic. The afferent arterioles deliver blood into glomeruli—capillary networks that produce a blood filtrate that enters the urinary tubules. The blood remaining in a glomerulus leaves through an efferent arteriole, which delivers the blood into another capillary network—the peritubular capillaries surrounding the renal tubules.
This arrangement of blood vessels is unique. It is the only one in the body in which a capillary bed (the glomerulus) is drained by an arteriole rather than by a venule and delivered to a second capillary bed located downstream (the peritubular capillaries). Blood from the peritubular capillaries is drained into veins that parallel the course of the arteries in the kidney. These veins are called the interlobular veins, arcuate veins, and inter-lobar veins. The interlobar veins descend between the pyramids, converge, and leave the kidney as a single renal vein, which empties into the inferior vena cava.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.