Which structure is the first stage of urine formation?

• A. Glomerulus
• B. Bowman's capsule
• C. Loop of Henle
• D. Proximal tubule

Answer: (A)

The first stage of urine formation is filtration in the glomerulus. Blood pressure forces water and small solutes through the glomerular filtration barrier into Bowman's space, creating the filtrate. Bowman's capsule simply collects that filtrate, which then moves into the tubules for reabsorption and secretion to become urine. The glomerulus is the initiation point because filtration happens there, while the other structures participate downstream in processing the filtrate.