Most important buffering system is?

Correct Answer: C

Rationale: The bicarbonate buffer system (HCO₃⁻/H₂CO₃) is the most important in blood, rapidly neutralizing acids or bases via CO₂ exhalation (lungs) and HCO₃⁻ regulation (kidneys). It handles ~70% of extracellular buffering. Proteins (D) and phosphate (B) contribute less, and bone (A) is a long-term reserve, making C the primary system.

Correct Answer: C

Rationale: Glomerular filtration's primary function is filtering blood to form an initial filtrate (C), passing water, electrolytes, and waste into Bowman's capsule while retaining proteins and cells. Reabsorption (A) and ion transport (B) occur in tubules, and pH regulation (D) is a broader kidney role, making C the specific glomerular step.

Correct Answer: D

Rationale: Decreased albumin (A) reduces oncotic pressure, vasodilation of the afferent arteriole (B) increases glomerular pressure, and efferent vasoconstriction (C) raises it further, all boosting GFR. All are true: low albumin lessens opposition, afferent dilation enhances flow, and efferent constriction traps pressure, making E (all are correct), reassigned as D, correct.

Correct Answer: D

Rationale: Nonvolatile acids (e.g., sulfuric, phosphoric) arise from metabolism and protein breakdown (D), requiring renal excretion. They must be eliminated (A is false), volatile acids (COâ‚‚) exceed them (B is false), and bone buffers partially (C is false), making D correct.

Correct Answer: D

Rationale: The bladder lies posterior to the pubic symphysis (D), a key anatomical position. It has smooth muscle (detrusor), not skeletal (A), connects to the urethra, not ureter (B), and is innervated by pelvic nerves, not cranial XI (C), making D the correct feature.