Which of the following is NOT modified by the kidneys to regulate the pH of ECF?

Correct Answer: C

Rationale: The correct answer is C: PO 3- secretion. The kidneys regulate pH by either excreting H+ ions or reabsorbing HCO3- ions. NH3 secretion helps in buffering H+ ions, while HCO3- excretion helps in regulating blood pH. PO 3- secretion does not directly affect pH regulation in the extracellular fluid. Hence, it is not modified by the kidneys to regulate pH.

Correct Answer: C

Rationale: Rationale: The correct answer is C: chloride. The serum anion gap is calculated by subtracting the sum of bicarbonate and chloride from sodium. Chloride is the primary anion contributing to the serum anion gap, as it plays a crucial role in maintaining electrical neutrality. Phosphate (A) and bicarbonate (B) are not included in the calculation of the serum anion gap. Sodium (D) is a cation, not an anion, so it does not directly contribute to the anion gap. Therefore, chloride is the correct answer as it is a major anion contributing to the serum anion gap.

Correct Answer: B

Rationale: Step 1: The internal pool includes various substances like nutrients, waste products, and ions. Step 2: Substances can also be removed through metabolic processes like oxidation or conversion. Step 3: Excretion is not the sole method; other ways include sweat, breath, or shedding skin. Step 4: Therefore, the statement that excretion is the only way for substances to be removed from the internal pool is false.

Correct Answer: B

Rationale: The correct answer is B: FALSE. Estrogen does not directly affect body water composition. The main reason women generally have more body water than men is due to differences in body composition, such as higher body fat percentage in women. Estrogen primarily influences fat distribution, not body water levels. Choices A, C, and D are incorrect because estrogen's effect on adipose tissue does not directly impact body water content in individuals.

Correct Answer: A

Rationale: 1. Synovial fluid is a type of transcellular fluid that surrounds the joints - TRUE. 2. Synovial fluid is a clear, viscous fluid found in the cavities of synovial joints. 3. It provides lubrication, nourishment, and shock absorption to the joints. 4. It is produced by the synovial membrane and helps reduce friction between the joint surfaces. 5. Therefore, the statement is accurate, making choice A the correct answer.