Which cell in the collecting tubule of the renal tubules functions in maintaining acid-base balance?

Correct Answer: B

Rationale: Intercalated cells in the collecting tubule are specialized for acid-base homeostasis. They exist in two types: Type A secretes hydrogen ions (H⁺) into the tubular lumen to correct acidosis, while Type B secretes bicarbonate (HCO₃⁻) to correct alkalosis. This active regulation of blood pH distinguishes them from principal cells, which handle sodium and water balance under aldosterone and ADH influence. Juxtaglomerular cells and podocytes are not in the collecting tubule, making B the accurate answer.

Correct Answer: A

Rationale: When urination is inconvenient, the brain (pons and cortex) sends inhibitory signals via descending spinal pathways to suppress the sacral micturition reflex. This overrides pelvic nerve-mediated detrusor contraction and reinforces pudendal nerve control of the external sphincter, delaying voiding until appropriate, making A (True) correct.

Correct Answer: C

Rationale: Antidiuretic hormone (ADH) is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus by magnocellular neurons. It's then transported to the posterior pituitary (neurohypophysis) for storage and release. The posterior pituitary (A, D) doesn't synthesize it, and the anterior pituitary (B) produces other hormones, making C correct.

Correct Answer: C

Rationale: A pH of 6.90 (severe acidosis), HCO₃⁻ of 13 mEq/L (low), and PaCO₂ of 68 mmHg (high) indicate combined metabolic acidosis (low HCO₃⁻ from overdose, e.g., lactic acid) and respiratory acidosis (high PCO₂ from hypoventilation due to sedation). No compensation is evident (HCO₃⁻ isn't rising), ruling out A, B, D, making C correct.

Correct Answer: C

Rationale: Crohn's disease, an inflammatory bowel condition, requires a low-fiber diet to reduce irritation, and high protein and calories (C) to support healing and nutrition during flares. High fiber (A) worsens symptoms, potassium (B, D) isn't the focus unless deficient, making C the recommended diet.