Final answer:
The structure where blood filtration occurs and that contains a mass of capillaries called the glomerulus is the renal corpuscle.
Step-by-step explanation:
A structure composed of a mass of capillaries called the glomerulus and where blood filtration occurs is known as a renal corpuscle. Within the renal corpuscle, blood enters through an afferent arteriole into the glomerulus, where filtration of the blood takes place under pressure. This process results in water and solutes being filtered out of the blood and into the space created by Bowman's capsule. The renal corpuscle includes the glomerulus and the Bowman's (glomerular) capsule and is located in the renal cortex of the kidney.
The renal corpuscle is the initial stage where the blood plasma is filtrated, and this filtration forms a filtrate that passes into Bowman's capsule then into the proximal end of the renal tubule. The renal tubule consists of the proximal convoluted tubule (PCT), the loop of Henle, and the distal convoluted tubule (DCT), which form a sophisticated system for modifying the filtrate into urine through reabsorption and secretion functions.