The nitrogen that must be excreted comes from:

Correct Answer: C

Rationale: Nitrogen for excretion comes from protein deamination e.g., liver converts amino acids to urea. Carbohydrates yield COâ‚‚/Hâ‚‚O not nitrogen. Nitric buffer isn't a system false. Atmosphere provides Oâ‚‚ not waste N. Deamination distinguishes it, critical for nitrogen source, unlike carbs or external origins.

Correct Answer: A

Rationale: Vasa recta is a capillary network around Loop of Henle e.g., countercurrent exchanger maintains gradient. Urethra is exit not capillaries. Hypothalamus makes ADH not vasa recta. Zona glomerulosa is aldosterone not vascular. Capillary role distinguishes it, key to medullary osmolality, unlike tubes or hormones.

Correct Answer: B

Rationale: Tubular damage (intrarenal failure) impairs urine concentration, fixing specific gravity at 1.010 (isosthenuric, like plasma), unlike hematuria (variable causes), low sodium (prerenal), or low osmolality (not specific). This reflects lost tubular function, distinguishing intrarenal pathology, key for diagnosing acute tubular necrosis versus prerenal hypoperfusion.

Correct Answer: D

Rationale: Hard candy (sugar) suits chronic renal disease, avoiding raisins (potassium), ice cream (protein), and pickles (sodium) unrestricted unless diabetic. This distinguishes dietary safety, key for electrolyte balance, contrasting with high-risk options.

Correct Answer: B

Rationale: Chronic rejection involves gradual vascular occlusion, reducing perfusion not recurrence (separate), T-cell attack (acute), or antibodies (hyperacute). This distinguishes chronic rejection's mechanism, key for long-term management, contrasting with acute processes.