Body Fluids MCQ for MRCP USMLE AMC MRCS – Part 1

1. Extracellular fluid in adults differs from intracellular fluid in that its
A. Volume is greater.
B. Tonicity is lower.
C. Anions are mainly inorganic.
D. Sodium: Potassium molar ratio is higher.
E. pH is lower.

Answer with Explanation of Question No 1
A. False. Cells contain half to two-thirds of the total body fluid.
B. False. It is the same; if it were lower, osmosis would draw water into the cells.
C. True. Mainly Cl and HCO3inside the ECF, the main anions are protein and organic phosphates in ICF.
D. True. Around 30:1 in ECF; the intracellular ratio is about 1:10.
E. False. Intracellular pH is lower due to cellular metabolism.


2. Blood group antigens (agglutinogens) are
A. Carried on the haemoglobin molecule.
B. Beta globulins.
C. Equally immunogenic.
D. Not present in the fetal blood.
E. Inherited as recessive Mendelian characteristics.

Answer with Explanation of Question No 2
A. False. They are part of the red cell membrane.
B. False. They are glycoproteins.
C. False. A, B and D antigens are more immunogenic than the others.
D. False. Fetal blood may elicit immune responses if it enters the maternal circulation.
E. False. They are Mendelian dominants.

3. Total body water expressed as a percentage of body weight
A. Can be measured with an indicator dilution technique using deuterium oxide.
B. Is smaller on average in women than in men.
C. Rises following injection of posterior pituitary extracts.
D. Falls during starvation.
E. Is less than 80 percent in young adults.

Answer with Explanation of Question No 3
A. True. D2O (heavy water) exchanges with water in all body fluid compartments.
B. Tru.e Women carry relatively more fat than men and fat has a low water content.
C. True. ADH in the extracts inhibits water excretion by the kidneys.
D. False. It rises as fat stores are metabolized to provide energy. (fat has a low water content)
E. True. 70 percent, the percentage in the lean body mass, is about the maximum percent possible.

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