Final answer:
The glomerulus is the capillary bed that is fed by the afferent arteriole and drained by the efferent arteriole in the kidney's nephron.
Step-by-step explanation:
The capillary bed that is fed by the afferent arteriole and drained by the efferent arteriole is the glomerulus. In the kidney's nephron, the afferent arteriole forms a high-pressure capillary tuft known as the glomerulus, which filters the blood. The filtered blood then passes through the efferent arteriole, which leads to a second capillary network, comprising the peritubular capillaries and vasa recta that surround the renal tubule and are involved in the reabsorption of solutes and water back into the circulation. It is notable that the macula densa cells are part of the juxtaglomerular apparatus (JGA) and are involved in regulating the function of the nephron but are not a capillary bed.