What is the correct sequence for urine formation steps?

What is the correct sequence for urine formation steps?

• A. Filtration, Re-absorption, Secretion, Urine Excretion
• B. Filtration, Secretion, Re-absorption, Urine Excretion
• C. Secretion, Filtration, Re-absorption, Urine Excretion
• D. Filtration, Urine Excretion, Re-absorption, Secretion

Answer: (A)

The sequence starts with filtration at the glomerulus, where blood plasma is filtered to form a filtrate. Next, reabsorption occurs along the tubules, returning most water, nutrients, and essential ions from the filtrate back into the bloodstream. After that, secretion adds additional wastes from the blood into the tubule fluid to be removed. Finally, the remaining filtrate is excreted as urine from the body. This order—filtration, reabsorption, secretion, excretion—reflects how the kidney first creates a filtrate, then adjusts its content, and finally disposes of the final urine.

The sequence starts with filtration at the glomerulus, where blood plasma is filtered to form a filtrate. Next, reabsorption occurs along the tubules, returning most water, nutrients, and essential ions from the filtrate back into the bloodstream. After that, secretion adds additional wastes from the blood into the tubule fluid to be removed. Finally, the remaining filtrate is excreted as urine from the body. This order—filtration, reabsorption, secretion, excretion—reflects how the kidney first creates a filtrate, then adjusts its content, and finally disposes of the final urine.