Final answer:
The afferent arteriole brings blood to the glomerulus, and the efferent arteriole carries it away, both playing crucial roles in the kidney's filtration process.
Step-by-step explanation:
In a nephron, the afferent arteriole delivers blood to the glomerulus, while the efferent arteriole carries blood away from it. The nephron is the functional unit of the kidney that filters blood to form urine. Blood enters the kidney through the renal artery, which branches into many capillaries including those of the glomerulus. The high pressure in these capillaries helps filter blood plasma into Bowman's capsule, starting the urine formation process. The remaining blood, after filtration, leaves the glomerulus via the efferent arteriole and moves into the peritubular capillaries and vasa recta, which are involved in the reabsorption and secretion processes of the nephron. Both the afferent and efferent arterioles are critical for regulating blood flow and pressure within the glomerulus and thereby influence the rate of filtration and urine production.