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Questions and Answers
What percentage of body weight does total body water (TBW) constitute in a typical adult male?
What percentage of body weight does total body water (TBW) constitute in a typical adult male?
- 50%
- 70%
- 60% (correct)
- 75%
Which factor contributes to a lower total body water (TBW) in females compared to males?
Which factor contributes to a lower total body water (TBW) in females compared to males?
- Increased age
- Lower metabolic rate
- Higher muscle mass
- Higher body fat content (correct)
In a 70 kg male, how much of the total body water is classified as intracellular fluid?
In a 70 kg male, how much of the total body water is classified as intracellular fluid?
- 14L
- 35L
- 28L (correct)
- 42L
What body fluid compartment accounts for 15% of total body weight in a healthy adult male?
What body fluid compartment accounts for 15% of total body weight in a healthy adult male?
What happens to total body water (TBW) as a person ages?
What happens to total body water (TBW) as a person ages?
What is the primary function of transcellular fluid?
What is the primary function of transcellular fluid?
Which of the following is NOT considered a type of transcellular fluid?
Which of the following is NOT considered a type of transcellular fluid?
What significant effect does the loss of digestive juices have on the body?
What significant effect does the loss of digestive juices have on the body?
How do plasma and interstitial fluid (ISF) differ?
How do plasma and interstitial fluid (ISF) differ?
What occurs during the exchange of fluids among body compartments?
What occurs during the exchange of fluids among body compartments?
Which body fluid is not typically part of the transcellular fluid category?
Which body fluid is not typically part of the transcellular fluid category?
What primarily contributes to the higher concentration of proteins in plasma compared to interstitial fluid (ISF)?
What primarily contributes to the higher concentration of proteins in plasma compared to interstitial fluid (ISF)?
Which is a characteristic feature of the exchange between plasma and ISF?
Which is a characteristic feature of the exchange between plasma and ISF?
What could potentially disrupt the balance of transcellular fluid?
What could potentially disrupt the balance of transcellular fluid?
Which of the following ions has the highest concentration in extracellular fluid (ECF)?
Which of the following ions has the highest concentration in extracellular fluid (ECF)?
What is the main anion found in intracellular fluid (ICF)?
What is the main anion found in intracellular fluid (ICF)?
What is the normal concentration of potassium ions ($K^+$) in intracellular fluid (ICF)?
What is the normal concentration of potassium ions ($K^+$) in intracellular fluid (ICF)?
How does hydrostatic pressure influence fluid movement between compartments?
How does hydrostatic pressure influence fluid movement between compartments?
Which compartment has a higher concentration of calcium ions ($Ca^{2+}$)?
Which compartment has a higher concentration of calcium ions ($Ca^{2+}$)?
Which of these is a true statement regarding protein concentration in ECF and ICF?
Which of these is a true statement regarding protein concentration in ECF and ICF?
What is the concentration of glucose in intracellular fluid (ICF)?
What is the concentration of glucose in intracellular fluid (ICF)?
Which formula is used to calculate blood volume?
Which formula is used to calculate blood volume?
What condition is characterized by water gain exceeding water loss?
What condition is characterized by water gain exceeding water loss?
Which of the following is NOT a source of water loss in the body?
Which of the following is NOT a source of water loss in the body?
Which statement about extracellular fluid (ECF) is true?
Which statement about extracellular fluid (ECF) is true?
Evan's blue is primarily used to measure which bodily component?
Evan's blue is primarily used to measure which bodily component?
What is a requirement for an indicator used to measure total body water (TBW)?
What is a requirement for an indicator used to measure total body water (TBW)?
Which of the following indicators can be used to measure extracellular fluid (ECF)?
Which of the following indicators can be used to measure extracellular fluid (ECF)?
Which equation correctly expresses the relationship between ECF, ISF, and plasma?
Which equation correctly expresses the relationship between ECF, ISF, and plasma?
What characteristic of an indicator used for measuring plasma volume allows it to be measured accurately?
What characteristic of an indicator used for measuring plasma volume allows it to be measured accurately?
What is the purpose of hematocrit in blood volume calculation?
What is the purpose of hematocrit in blood volume calculation?
Which indicator can be used to determine blood volume directly?
Which indicator can be used to determine blood volume directly?
Why must an indicator for measurement be non-toxic?
Why must an indicator for measurement be non-toxic?
What is the primary limitation of directly measuring interstitial fluid (ISF)?
What is the primary limitation of directly measuring interstitial fluid (ISF)?
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Study Notes
Body Fluid Composition
- 60% of the adult human body is comprised of fluid, primarily a water solution with ions and other substances.
- Total body water (TBW) in a 70 kg adult male is approximately 42 liters.
- Body fat content, sex, and age influence TBW.
- Fat tissues have low water content, leading to lower TBW in obese individuals.
- Females have lower TBW compared to males due to a higher body fat percentage.
- Young people have a greater percentage of TBW compared to older individuals.
TBW Distribution
- Intracellular fluid (ICF) makes up 2/3 of TBW, equating to 40% of body weight (28L).
- Extracellular fluid (ECF) comprises 1/3 of TBW, equating to 20% of body weight (14L).
- Intravascular fluid, a component of ECF, includes plasma, making up 5% of body weight (3.5L).
- Interstitial fluid, another ECF component, accounts for 15% of body weight (10.5L).
Human Circulatory System
- The circulatory system consists of a pulmonary circuit and a systemic circuit, facilitating blood flow throughout the body.
- Capillaries, tiny blood vessels, play a crucial role in the filtration and absorption processes within tissues.
Transcellular Fluid
- Transcellular fluid is a minor ECF compartment, found in various body cavities for specialized functions.
- Cerebrospinal fluid, intraocular fluid, synovial fluid, pericardial, intrapleural, and peritoneal fluids, and digestive juices are examples of transcellular fluids.
- These fluids do not significantly impact overall fluid balance, except for digestive juices, whose loss in conditions like vomiting or diarrhea can lead to fluid imbalance.
Ionic Composition Differences
- There is a constant exchange between different body fluid compartments, maintaining a dynamic equilibrium.
- Exchange occurs between ICF and ISF through plasma membranes and between plasma and ISF through capillary walls.
- Plasma and interstitial fluid share similar ionic compositions, with the notable exception that ISF lacks plasma proteins.
- The main difference between ECF and ICF is the significantly higher concentration of proteins within the ICF.
Key Differences in ECF and ICF Compositions
| ECF | ICF | |
|---|---|---|
| $Na^+$ | 142 mEq/L | 10 mEq/L |
| $K^+$ | 4 mEq/L | 140 mEq/L |
| $Ca^{2+}$ | 2.4 mEq/L | 0.0001 mEq/L |
| $Mg^{2+}$ | 1.2 mEq/L | 58 mEq/L |
| $Cl^-$ | 103 mEq/L | 4 mEq/L |
| $HCO_3^-$ | 24 mEq/L | 10 mEq/L |
| Phosphates | 4 mEq/L | 75 mEq/L |
| $SO_4^{2-}$ | 1 mEq/L | 2 mEq/L |
| Glucose | 90 mg/dl | 0 to 20 mg/dl |
| Amino acids | 30 mg/dl | 200 mg/dl |
| Cholesterol | 0.5 g/dl | 2 to 95 g/dl |
| $PO_2$ | 35 mm Hg | 20 mm Hg |
| $PCO_2$ | 46 mm Hg | 50 mm Hg |
| pH | 7.4 | 7.0 |
| Proteins | 2 g/dl | 16 g/dl |
Cations and Anions in ECF and ICF
| ICF | ECF | |
|---|---|---|
| Cations | $K^+$ | $Na^+$ |
| Anions | Phosphates and proteins | $Cl^-$ and $HCO_3^-$ |
Protein Distribution
- ICF contains a higher concentration of protein than ECF due to the impermeability of the cell membrane to proteins.
- Plasma has a higher protein concentration than ISF because of the limited permeability of the capillary wall to large proteins.
Indicator-Dilution Principle for Volume Measurement
- The indicator-dilution principle is used to measure body fluid compartment volumes by introducing a substance (indicator) and measuring its dilution in the compartment.
- The indicator should:
- Be distributed in the target compartment.
- Not be metabolized or excreted.
- Not affect the distribution of body water.
- Be inert, non-toxic, easily measurable, and stable during the measurement period.
Indicators for Specific Compartments
| Compartment | Indicator Characteristics | Indicator |
|---|---|---|
| TBW | Distributed in all compartments | Deuterium oxide, Tritium oxide, Antipyrine |
| ECF | Distributed in plasma and ISF | Inulin, Thiosulfate, Thiocyanate, Sucrose, Mannitol, Radioactive sodium, and bromide |
| Plasma | Restricted to plasma | Evan's blue, Radioactive albumin |
| Blood volume | - | Chromium-51 labeled RBCs |
Calculating ISF and ICF Volumes
- ECF= Plasma + ISF
- ISF = ECF - Plasma
- TBW = ICF + ECF
- ICF = TBW - ECF
Blood Volume Measurement
- Total blood volume accounts for 8% of body weight.
- Blood consists of plasma (fluid, 55%) and blood cells (RBCs, WBCs, and platelets, 45%).
- Hematocrit value represents the percentage of RBCs in the total blood volume (45% or 0.45).
- Blood,volume calculation methods:
- Determining hematocrit and plasma volume (using Evan's blue or radioactive albumin).
- Blood volume = plasma volume / (1- hematocrit)
- Measuring RBCs volume using radioactive material (chromium-51 labeled RBCs).
- Blood volume = RBCs volume x 100 / hematocrit
- Determining hematocrit and plasma volume (using Evan's blue or radioactive albumin).
Water Balance
| Water Balance | Normal Activity and Moderate Temperature |
|---|---|
| Water Gain Sources | Water Loss Sources |
| Food and drinking (2.2 L/day) | Urine (1.5 L/day) |
| Body oxidative metabolism (0.3 L/day) | Insensible water loss (0.9 L/day) |
| Intravenous fluid infusion (disease) | Diarrhea and vomiting (disease) |
- Water gain exceeding water loss leads to overhydration or water overload.
- Water loss exceeding water gain results in dehydration.
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