Question

which stage of urine production involves the removal of substances from the bloodstream?
a reabsorption
b excretion
c filtration
d secretion

Explanation:

• Reabsorption: It is the process of moving substances from the filtrate back into the bloodstream, not removing substances from the bloodstream.
• Excretion: Excretion is the final process of eliminating urine (already - formed waste) from the body, not directly related to removing substances from the bloodstream.
• Filtration: Filtration in the kidneys (in the glomerulus) forces water and small - sized solutes (such as urea, salts, glucose) from the blood plasma into the renal tubule. This is the initial step where substances are removed from the bloodstream.
• Secretion: Secretion is the process of actively transporting substances (such as hydrogen ions, potassium ions, some drugs) from the peritubular capillaries into the renal tubule. It is a more targeted addition of substances to the filtrate rather than the broad - based removal like filtration.

Answer:

C. filtration