Question

which stage of urine production involves adding ammonia, uric acid, and other waste substances directly into the renal tubule?
a reabsorption
b filtration
c secretion
d excretion

Explanation:

• Reabsorption: In this stage, useful substances like glucose, water, and electrolytes are re - absorbed from the filtrate back into the bloodstream, not adding waste.
• Filtration: This is the initial stage where blood is filtered through the glomerulus to form a filtrate. It is mainly about separating blood components, not adding waste to the renal tubule.
• Secretion: In this stage, substances such as ammonia, uric acid, and some drugs are actively transported from the peritubular capillaries into the renal tubule.
• Excretion: This is the final process of eliminating urine (already formed through reabsorption, filtration, and secretion) from the body.

Answer:

C. secretion