Answer: Nitrogenous wastes diffuse out down their gradient while useful solutes stay.
- A Red blood cells pass freely into the dialysing fluid in most observed cases
- B Nitrogenous wastes diffuse out down their gradient while useful solutes stay
- C Plasma proteins diffuse out of the blood into the fluid in standard reference material
- D Water is pumped into the blood from the dialysing fluid under most conditions studied
Correct answer: B. Nitrogenous wastes diffuse out down their gradient while useful solutes stay
Explanation: Because the dialysing fluid lacks nitrogenous wastes, these substances diffuse out of the blood down their concentration gradient across the dialysis membrane, while essential solutes at similar concentrations are retained in the blood.
Filtrate flows through four functionally distinct stages of the nephron: Bowman's capsule filters blood, the PCT reabsorbs most useful substances unconditionally, the Loop of Henle builds a concentration gradient via counter-current exchange, the DCT secretes selected substances, and the collecting duct performs the final ADH-controlled water reabsorption.
Concept context
Nitrogenous waste, kidney structure, urine formation in the nephron, and hormonal regulation of excretion.
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