What is the definition of the tubular secretion?

Correct Answer: B

Rationale: Tubular secretion is the selective transfer of substances, such as hydrogen ions (H⁺), potassium (K⁺), and organic compounds, from the peritubular capillaries (blood) into the tubular lumen (urine). This process, occurring mainly in the proximal and distal convoluted tubules, helps eliminate waste and regulate blood pH and ion levels. It differs from reabsorption (A), glomerular filtration (C), and water reabsorption (D), making B the correct definition.

Correct Answer: C

Rationale: The thin descending limb of the Loop of Henle is highly permeable to water due to aquaporin-1 channels, allowing water to exit into the hyperosmotic medullary interstitium, concentrating the filtrate. The thick ascending limb is impermeable to water, actively reabsorbing Na⁺ and Cl⁻, and the thin ascending limb has limited water permeability, making C correct.

Correct Answer: B

Rationale: Most human enzymes function optimally at a physiological pH of 7.4, close to blood pH (7.35-7.45), where their active sites maintain proper conformation for catalysis. A pH of 7.8 (A) is slightly alkaline, 6.8 (C) is too acidic for most, and 2 (D) suits gastric enzymes like pepsin, not the majority, making B correct.

Correct Answer: A

Rationale: Atelectasis, the collapse of lung alveoli, is the most common preventable complication after abdominal surgery due to shallow breathing from pain or anesthesia effects. It's mitigated by deep breathing exercises and incentive spirometry. Fluid imbalance (B), thrombophlebitis (C), and urinary retention (D) occur but are less frequent and often less preventable with routine nursing interventions, making A the correct answer.

Correct Answer: B

Rationale: The kidneys' primary function is blood filtration (B), removing waste (e.g., urea), regulating electrolytes, and maintaining fluid/acid-base balance via glomeruli, producing filtrate for urine. Storage (A) is the bladder's role, contractions (C) aid micturition, and urethra expansion (D) is minor, making B the core function.