The kidneys produce renin. Explain the function of renin.

Correct Answer: A

Rationale: Renin activates angiotensin cleaves angiotensinogen to angiotensin I (e.g., JGA response to low BP), triggering RAAS. Vitamin D activation is kidney's calcitriol role not renin. RBC stimulation is erythropoietin not renin. Vasoconstriction is angiotensin II downstream. Renin's angiotensin initiation distinguishes it, critical for BP regulation, unlike unrelated or subsequent effects.

Correct Answer: C

Rationale: Glomerular filtration occurs between glomerulus and glomerular capsule plasma filters into Bowman's space (e.g., GFR). Afferent/peritubular are vascular not filtration site. Efferent/peritubular are post-filtration incorrect. Peritubular/tubule is reabsorption not filtration. Glomerulus-capsule interface distinguishes it, critical for filtrate formation, unlike vascular or tubular errors.

Correct Answer: C

Rationale: Females have lower water percentage (~50% vs. males ~60%) due to more adipose tissue less water-rich than muscle (e.g., fat ~10% water, muscle ~75%). Higher water contradicts fat lowers. Muscle increases water opposite. Lower muscle isn't primary adipose key. Adipose's impact distinguishes it, critical for sex differences, unlike muscle or reverse errors.

Correct Answer: C

Rationale: ANH increases Na /water excretion reduces blood volume/BP (e.g., heart stretch response). Decrease contradicts ANH is natriuretic. Increase/increasing raises volume opposite. Increase/decreasing aligns distinguishes it, key to BP regulation, unlike retention or mismatched effects.

Correct Answer: B

Rationale: A buffer takes up excess H or OH⁻ e.g., HCO₃⁻ neutralizes (pH stability). Acid donates H not absorbs. Base takes H not OH⁻. Salt is neutral non-buffering. Buffer's dual capacity distinguishes it, key to homeostasis, unlike one-way or neutral substances.