Which renal tubule parts functions more in secretion?

Correct Answer: B

Rationale: The distal convoluted tubule (DCT) is the primary site for secretion in the renal tubule system. It actively secretes substances such as hydrogen ions, potassium, and certain drugs from the peritubular capillaries into the tubular lumen, aiding in waste elimination and pH regulation. Unlike the proximal convoluted tubule, which is lined with microvilli and excels at reabsorption, the DCT lacks microvilli, enhancing its secretory role. The Loop of Henle focuses on creating a concentration gradient, and the collecting duct adjusts water and electrolyte balance, making the DCT the correct answer for secretion.

Correct Answer: A

Rationale: Renal clearance measures the volume of plasma cleared of a substance per unit time, reflecting kidney function. For substances like creatinine, clearance approximates GFR, indicating filtration efficiency. Abnormal clearance suggests impaired glomerular or tubular function, making it a valuable diagnostic tool, thus A (True) is correct.

Correct Answer: B

Rationale: Fluid in the proximal convoluted tubule (PCT) is isosmotic (~300 mOsm/L), as water and solutes (e.g., Na⁺, Cl⁻) are reabsorbed proportionally via leaky epithelium and aquaporins. This maintains osmolarity similar to plasma. It's not hyperosmotic (A) or hypoosmotic (C), and ADH affects later segments (D), making B correct.

Correct Answer: C

Rationale: Respiratory alkalosis (high pH, low PCOâ‚‚) results from hyperventilation, seen in fever (A), anxiety (B), and salicylate toxicity (D) due to stimulated breathing. Laryngeal obstruction (C) restricts airflow, causing COâ‚‚ retention (respiratory acidosis, low pH, high PCOâ‚‚), not alkalosis, making C the exception.

Correct Answer: B

Rationale: Activity intolerance post-myocardial infarction reflects reduced cardiac capacity. An outcome like ambulating 50 feet without dyspnea (B) is specific, measurable, and aligns with improving tolerance. Smoking cessation (A) is unrelated, no dyspnea on exertion (C) is vague, and tolerating activity (D) lacks specificity, making B correct.