Answer: One million.
- A One thousand
- B One million
- C One hundred
- D Just ten
Correct answer: B. One million
Explanation: Each human kidney contains roughly a million nephrons, its filtering units.
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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