Answer: Liver.
- A Liver
- B Kidney
- C Lungs
- D Pancreas
Correct answer: A. Liver
Explanation: Ammonia produced from protein metabolism is converted to the less toxic urea in the liver via the ornithine cycle, then transported to kidneys for excretion.
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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