Body Fluid Compartments and Composition Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Body Fluid Compartments and Composition. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Body Fluid Compartments and Composition Indian Medical PG Question 1: Which of the following is true regarding Na+ (sodium) ions?
- A. Does not help other ions in transport
- B. Responsible for depolarization (Correct Answer)
- C. Responsible for the resting membrane potential
- D. Sodium ion is responsible for Donnan effect
Body Fluid Compartments and Composition Explanation: ***Responsible for depolarization***
- The rapid influx of **Na+ ions** into the cell through voltage-gated sodium channels is the primary event that causes **depolarization** during an action potential.
- This influx makes the inside of the cell more positive, shifting the membrane potential from negative toward positive values.
*Sodium ion is responsible for Donnan effect*
- The **Donnan effect** describes the unequal distribution of permeable ions across a semi-permeable membrane due to the presence of impermeant charged molecules (e.g., proteins).
- **Na+ ions are small, permeable ions** - they do not create the Donnan effect. The effect is caused by large, non-diffusible charged molecules like proteins, not by sodium ions.
*Does not help other ions in transport*
- The **sodium-potassium pump (Na+/K+-ATPase)** actively transports Na+ out of the cell and K+ into the cell, maintaining their concentration gradients.
- These Na+ gradients are crucial for **secondary active transport**, where the energy from Na+ moving down its electrochemical gradient is used to move other ions (e.g., in Na+-glucose cotransport) or molecules against their gradients.
*Responsible for the resting membrane potential*
- The **resting membrane potential** is primarily established by the differential permeability of the membrane to K+ ions and the activity of the Na+/K+-ATPase.
- While Na+ leaking into the cell contributes slightly, the dominant factor is the efflux of **K+ ions** through leak channels, as the membrane is much more permeable to K+ than to Na+ at rest.
Body Fluid Compartments and Composition Indian Medical PG Question 2: Major ions in ECF are:
- A. Potassium and phosphate
- B. Sodium and phosphate
- C. Potassium and chloride
- D. Sodium and chloride (Correct Answer)
Body Fluid Compartments and Composition Explanation: ***Sodium and chloride***
- **Sodium (Na+)** is the primary cation, and **chloride (Cl-)** is the primary anion in the extracellular fluid (ECF).
- These ions play crucial roles in maintaining **osmotic pressure**, **fluid balance**, and **nerve impulse transmission**.
*Potassium and phosphate*
- **Potassium (K+)** is the major intracellular cation, while **phosphate (PO43-)** is a major intracellular anion.
- While present in the ECF, their concentrations are significantly lower compared to sodium and chloride.
*Sodium and phosphate*
- **Sodium** is a major ECF cation, but **phosphate** is predominantly an intracellular anion.
- Therefore, phosphate is not considered one of the major extracellular ions.
*Potassium and chloride*
- **Potassium** is primarily an intracellular ion, not a major ECF cation.
- While **chloride** is a major ECF anion, its pairing with potassium does not represent the two major ions in the ECF.
Body Fluid Compartments and Composition Indian Medical PG Question 3: Major portion of body water lies in:
- A. Extracellular
- B. Interstitial fluid
- C. Intracellular (Correct Answer)
- D. Plasma
Body Fluid Compartments and Composition Explanation: ***Intracellular***
- Approximately **two-thirds (60%)** of the total body water is located **inside cells** (intracellular fluid, ICF).
- In a 70 kg adult male, out of ~42L total body water, approximately **28L is intracellular**.
- This fluid is crucial for maintaining **cell volume**, metabolic processes, and overall cell function.
- The ICF contains high concentrations of potassium, magnesium, and phosphate.
*Extracellular*
- The **extracellular fluid (ECF)** compartment accounts for about **one-third (40%)** of the total body water (~14L in a 70 kg adult).
- While vital for nutrient and waste transport, it is a smaller volume compared to the intracellular compartment.
- ECF is further divided into interstitial fluid (~75% of ECF) and plasma (~25% of ECF).
*Interstitial fluid*
- Interstitial fluid is a **component of extracellular fluid**, not a major body water compartment on its own.
- It accounts for only about **10-11L** in a typical adult, which is less than the intracellular volume.
- It surrounds tissue cells and facilitates exchange between plasma and cells.
*Plasma*
- Plasma is the **smallest fluid compartment**, representing only about **3-3.5L** (~8% of total body water).
- While essential for circulation and transport, it contains far less water than the intracellular compartment.
- Plasma is the liquid component of blood, excluding cellular elements.
Body Fluid Compartments and Composition Indian Medical PG Question 4: Interstitial fluid volume can be measured by:
- A. Tritium oxide - Sodium thiosulfate
- B. Inulin - Serum albumin labelled with radioactive Iodine (Correct Answer)
- C. Inulin - Radioactive sodium
- D. Aminopyrine - Sucrose
Body Fluid Compartments and Composition Explanation: ***Inulin - Serum albumin labelled with radioactive Iodine***
- The **interstitial fluid volume** is calculated by subtracting the plasma volume from the extracellular fluid volume.
- **Inulin** is used to measure **extracellular fluid volume** because it freely distributes throughout the extracellular space but does not enter cells.
- **Serum albumin labeled with radioactive iodine** measures **plasma volume** as it stays primarily within the bloodstream due to its large size.
*Tritium oxide - Sodium thiosulfate*
- **Tritium oxide** (or D2O) is used to measure **total body water (TBW)**, as it distributes throughout all fluid compartments.
- **Sodium thiosulfate** is used to measure **extracellular fluid volume**, similar to inulin.
*Inulin - Radioactive sodium*
- While **inulin** measures **extracellular fluid volume**, **radioactive sodium** (typically 24Na) also measures extracellular fluid volume but can slightly overestimate it due to slow intracellular penetration.
- This combination doesn't directly provide a method for exclusively calculating interstitial fluid by subtraction from plasma volume.
*Aminopyrine - Sucrose*
- **Aminopyrine** is primarily used to measure the **volume of distribution of specific drugs** or gastric acid secretion, not fluid compartments.
- **Sucrose** can be used to measure **extracellular fluid volume** as it does not readily cross cell membranes, similar to inulin, but it's not the primary combination for measuring interstitial fluid from the given options.
Body Fluid Compartments and Composition Indian Medical PG Question 5: The body fluid compartments of a patient were measured, showing the following ion concentrations:
- Sodium (Na): $10 \mathrm{mEq} / \mathrm{L}$
- Potassium (K): $140 \mathrm{mEq} / \mathrm{L}$
- Chloride (Cl): $15 \mathrm{mEq} / \mathrm{L}$
Based on these values, which fluid compartment is being described?
- A. Plasma
- B. ICF (Correct Answer)
- C. Interstitial fluid
- D. ECF
Body Fluid Compartments and Composition Explanation: ***ICF***
- The measured ion concentrations, especially **high potassium (140 mEq/L)** and **low sodium (10 mEq/L)**, are characteristic of the **intracellular fluid (ICF)**, where potassium is the primary cation and sodium is kept low by the Na+/K+-ATPase pump.
- **Chloride levels (15 mEq/L)** are also significantly lower in the ICF compared to extracellular fluids.
*Plasma*
- Plasma typically has **high sodium (around 140 mEq/L)** and **low potassium (around 4 mEq/L)**, which contradicts the given measurements.
- Chloride levels in plasma are usually much higher, around **100-105 mEq/L**.
*Interstitial fluid*
- Interstitial fluid has an electrolyte composition very similar to plasma, with **high sodium** and **low potassium**, differing mainly in protein content.
- This composition is not consistent with the given measurements.
*ECF*
- The ECF (extracellular fluid), which includes both plasma and interstitial fluid, is characterized by **high sodium** and **low potassium**.
- The given ion concentrations, particularly the very **high potassium** and **low sodium**, are directly opposite to the typical ECF profile.
Body Fluid Compartments and Composition Indian Medical PG Question 6: Which of the following is NOT true about body fluids:
- A. Synovial fluid is transcellular fluid (Correct Answer)
- B. ECF volume of 70 kg adult man would be approximately 14 L
- C. The total body fluid per unit body weight is more in infants as compared to adults
- D. Intracellular fluid is 40% of total body weight
Body Fluid Compartments and Composition Explanation: ***Synovial fluid is transcellular fluid***
- This statement is **NOT true** according to most standard classifications.
- **Synovial fluid** is classified as a component of **interstitial fluid**, not transcellular fluid.
- **Transcellular fluid** refers to specialized fluids formed by active transport across epithelial membranes and includes cerebrospinal fluid (CSF), pleural fluid, peritoneal fluid, pericardial fluid, and digestive secretions.
- Synovial fluid, while specialized, is formed by ultrafiltration of plasma and secretion by synoviocytes, and is considered part of the interstitial compartment.
*ECF volume of 70 kg adult man would be approximately 14 L*
- This statement is **TRUE**.
- **Extracellular fluid (ECF)** constitutes approximately **20% of total body weight** in adult males.
- For a **70 kg man**: 20% × 70 kg = **14 kg ≈ 14 L** of ECF.
*The total body fluid per unit body weight is more in infants as compared to adults*
- This statement is **TRUE**.
- **Infants** have approximately **75-80% total body water (TBW)** compared to adults with **50-60% TBW**.
- This is due to higher metabolic rate, less fat tissue, and different body composition in infants.
*Intracellular fluid is 40% of total body weight*
- This statement is **TRUE**.
- **Intracellular fluid (ICF)** represents approximately **two-thirds of total body water**, which equals about **40% of total body weight** in adults.
- ICF is the largest fluid compartment in the body.
Body Fluid Compartments and Composition Indian Medical PG Question 7: Intracellular water constitutes what percentage of total body water?
- A. 25%
- B. 80%
- C. 40%
- D. 60% (Correct Answer)
Body Fluid Compartments and Composition Explanation: ***60%***
- **Intracellular fluid (ICF)** makes up approximately **two-thirds (67%)** of the total body water.
- Among the given options, **60% is the closest approximation** to the actual value.
- ICF refers to the fluid contained within cells, crucial for mediating cellular reactions and maintaining cell volume.
- ICF comprises about **40% of total body weight** (67% of 60% TBW).
*40%*
- This represents the approximate percentage of **total body weight** that is intracellular water, not the percentage of total body water.
- As a proportion of total body water, ICF is much higher (approximately 67%).
*25%*
- This value is significantly lower than the actual proportion of intracellular water.
- No major fluid compartment accounts for 25% of total body water.
*80%*
- This percentage is much higher than the actual proportion of intracellular water.
- An 80% proportion would be physiologically inconsistent with normal fluid distribution between ICF and ECF compartments.
Body Fluid Compartments and Composition Indian Medical PG Question 8: In which of the following conditions is blood osmolality increased?
- A. SIADH
- B. Psychogenic polydipsia
- C. Diarrhea (Correct Answer)
- D. Cerebral toxoplasmosis
Body Fluid Compartments and Composition Explanation: ***Diarrhea***
- Diarrhea leads to a significant loss of **water and electrolytes** from the body, primarily from the extracellular fluid compartment.
- This imbalance causes **hemoconcentration** and an increase in the concentration of solutes in the blood, thereby raising blood osmolality.
*SIADH*
- **Syndrome of Inappropriate Antidiuretic Hormone (SIADH)** is characterized by excessive secretion of ADH, leading to **dilutional hyponatremia**.
- The excess water retention dilutes the blood, resulting in **decreased serum osmolality**.
*Psychogenic polydipsia*
- This condition involves excessive water intake due to psychological factors, which causes **dilution of body fluids**.
- The increased water volume without a proportional increase in solutes leads to **decreased plasma osmolality**.
*Cerebral toxoplasmosis*
- **Cerebral toxoplasmosis** is an opportunistic infection of the brain, typically seen in immunocompromised individuals.
- It primarily causes neurological symptoms and **does not directly impact blood osmolality** unless complicated by other factors like dehydration or SIADH (which is not a primary effect).
Body Fluid Compartments and Composition Indian Medical PG Question 9: A patient with diabetes mellitus for the past 5 years presents with vomiting and abdominal pain. She is non-compliant with medication and appears dehydrated. Investigations revealed a blood sugar value of 500 mg/dl and the presence of ketone bodies. What is the next best step in management of this patient?
- A. Intravenous fluids
- B. Intravenous insulin
- C. Intravenous fluids with regular insulin (Correct Answer)
- D. Intravenous fluids with long-acting insulin
Body Fluid Compartments and Composition Explanation: Detailed management of diabetic ketoacidosis (DKA) requires both fluid resuscitation and insulin therapy.
***Intravenous fluids with regular insulin***
- The patient presents with classic signs of **diabetic ketoacidosis (DKA)**: hyperglycemia (blood sugar 500 mg/dl), ketone bodies, dehydration, and a history of diabetes non-compliance [1].
- Initial management for DKA involves aggressive **intravenous fluid resuscitation** to correct dehydration and then **intravenous regular insulin** to lower blood glucose and resolve ketosis [2].
*Intravenous fluids with long-acting insulin*
- While fluids are essential, **long-acting insulin** is not appropriate for the acute management of DKA because its slow onset of action makes it inefficient for rapidly correcting hyperglycemia and ketosis.
- **Regular insulin** is preferred as it has a quicker onset and shorter duration, allowing for more precise titration in an acute setting [2].
*Intravenous fluids*
- Although crucial for correcting **dehydration** and improving renal perfusion, fluids alone will not address the underlying **insulin deficiency** and **ketosis** that define DKA.
- Without insulin, the body will continue to produce ketones, exacerbating acidosis [3].
*Intravenous insulin*
- Giving intravenous insulin without prior or concomitant **fluid resuscitation** can be dangerous, as it can worsen **hypovolemia** and potentially lead to circulatory collapse by shifting glucose and potassium into cells.
- It is critical to first restore **circulating volume** before initiating insulin therapy [2].
Body Fluid Compartments and Composition Indian Medical PG Question 10: A man presents with deep burns covering 60% of his body. What is the immediate concern?
- A. Risk of infection
- B. Shock (Correct Answer)
- C. Potential for organ failure
- D. Development of sepsis
Body Fluid Compartments and Composition Explanation: ***Shock***
- Due to extensive body surface area involvement (60%), severe burns lead to massive **fluid loss** and a resultant decrease in circulating volume, immediately leading to **hypovolemic shock**.
- This fluid shift from the intravascular to the extravascular space occurs rapidly in the initial hours post-burn, making shock the most immediate life-threatening concern.
*Risk of infection*
- While a significant concern with large burns, **infection** typically becomes a major issue several hours to days after the initial injury, once the immediate threat of shock has been addressed.
- The immediate priority is maintaining hemodynamic stability before focusing directly on infection prevention.
*Potential for organ failure*
- **Organ failure** is a serious complication that can result from prolonged shock and systemic inflammatory response following severe burns.
- However, organ failure is a consequence of unmanaged shock rather than an immediate primary concern itself.
*Development of sepsis*
- **Sepsis** is a life-threatening organ dysfunction caused by a dysregulated host response to infection. It is a later complication, generally developing days after the burn injury.
- Sepsis is often triggered by **burn wound infection** and systemic inflammatory response, which occur after the initial hypovolemic phase.
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