Answer: Reabsorption of most filtered water along the tubules and collecting duct.
- A Reabsorption of most filtered water along the tubules and collecting duct
- B Secretion of extra water into the filtrate by the tubules according to most studies
- C Filtration of plasma proteins at the glomerulus under usual circumstances
- D A rise in glomerular filtration rate during the day in the majority of documented cases
Correct answer: A. Reabsorption of most filtered water along the tubules and collecting duct
Explanation: About 99% of the glomerular filtrate is reabsorbed along the tubules and collecting duct, mainly as water, concentrating the small remaining volume into urine.
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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