To increase the reabsorption of water, which parts of the kidney tubules are involved?

Correct Answer: A

Rationale: PCT (~65% water) and collecting duct (ADH-driven) increase water reabsorption e.g., bulk and regulated recovery. Distal tubule adjusts less water focus. Loop sets gradient not ADH-dependent. PCT/collecting synergy distinguishes it, key to water conservation, unlike partial or gradient-focused pairs.

Correct Answer: B

Rationale: Urine is ~95% water rest solutes (e.g., urea, ions ~5%). 100% ignores solutes false. 90% underestimates water too low. 85% overestimates solutes incorrect. 95% distinguishes it, critical for urine composition, unlike absolute or skewed estimates.

Correct Answer: D

Rationale: Skeletal system isn't directly influenced by kidneys bones respond indirectly via vitamin D (e.g., calcium). Cardiovascular is BP/volume direct. Respiratory ties to pH HCO₃⁻ effect. Endocrine involves hormones (renin) direct. Skeletal's indirect link distinguishes it, critical for system specificity, unlike directly impacted systems.

Correct Answer: A

Rationale: Glomerular capillaries have larger pores fenestrated (e.g., allow plasma filtration, not cells/proteins). Shorter length is false longer for GFR. Innervation is minimal not functional trait. Na absorption is tubular not glomerular. Pore size distinguishes it, key to filtration selectivity, unlike length, nerve, or absorption traits.

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.