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Questions and Answers
What is the primary differentiator in the ionic composition between plasma and interstitial fluid?
What is the primary differentiator in the ionic composition between plasma and interstitial fluid?
Which of the following is the primary cation found in intracellular fluid?
Which of the following is the primary cation found in intracellular fluid?
How does total body water (TBW) vary with an increase in water output?
How does total body water (TBW) vary with an increase in water output?
What is the concentration of chloride ions in plasma and interstitial fluid?
What is the concentration of chloride ions in plasma and interstitial fluid?
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Which factor has a significant impact on the movement of fluids between body compartments?
Which factor has a significant impact on the movement of fluids between body compartments?
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What percentage of total body water (TBW) is typically found in adult females?
What percentage of total body water (TBW) is typically found in adult females?
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Which compartment accounts for approximately 2/3 of total body water?
Which compartment accounts for approximately 2/3 of total body water?
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Which of the following represents the correct distribution of extracellular fluid (ECF) in a 70 kg male?
Which of the following represents the correct distribution of extracellular fluid (ECF) in a 70 kg male?
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What is the primary difference between intracellular fluid (ICF) and extracellular fluid (ECF)?
What is the primary difference between intracellular fluid (ICF) and extracellular fluid (ECF)?
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For a 70 kg male, what is the total body water (TBW) in liters?
For a 70 kg male, what is the total body water (TBW) in liters?
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Which fluid compartment is primarily composed of plasma?
Which fluid compartment is primarily composed of plasma?
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How much of the total blood volume, expressed as a percentage, corresponds to body weight?
How much of the total blood volume, expressed as a percentage, corresponds to body weight?
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What is the primary function of body water regarding cell membranes?
What is the primary function of body water regarding cell membranes?
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What is the primary difference in ionic composition between extracellular and intracellular fluids?
What is the primary difference in ionic composition between extracellular and intracellular fluids?
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Which of the following factors influences the total body water percentage in an individual?
Which of the following factors influences the total body water percentage in an individual?
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In a 70-kilogram adult man, approximately how much total body water is present?
In a 70-kilogram adult man, approximately how much total body water is present?
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How does total body water percentage change with aging?
How does total body water percentage change with aging?
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What is the significance of maintaining a relatively constant volume of body fluids?
What is the significance of maintaining a relatively constant volume of body fluids?
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Study Notes
Body Fluids
- Body fluids are essential for cell function and maintain a relatively constant volume and composition.
- Problems in clinical medicine can arise from abnormalities in the systems regulating body fluid constancy.
Percentage of Body Water
- In a 70kg adult male, total body water (TBW) is approximately 60% of body weight or about 42 liters.
- Percentage of TBW varies with age, gender, and obesity.
- TBW decreases with age, as body fat increases.
- Newborn and premature babies have a higher percentage of TBW (70-75%).
- Women typically have a lower percentage of TBW (50-55%) compared to men due to higher body fat content.
Body Water Distribution
- Total Body Water (TBW) is approximately 60% of the total body weight.
- Infant TBW is about 73%.
- Male adult TBW is about 60%.
- Female adult TBW is about 40-50%.
- Old age TBW is about 45%.
Body Water Functions
- Regulates body temperature.
- Transports nutrients and oxygen to cells.
- Produces oxygen.
- Helps transform nutrients into energy.
- Protects and hydrates organs.
- Helps absorb nutrients.
- Protects and lubricates joints.
- Represents 75% of muscles.
Fluid Compartments
- Extracellular fluid (ECF) is divided into:
- Plasma
- Interstitial fluid
- Transcellular fluid
- Intracellular fluid (ICF)
- ICF comprises about 2/3 of the total body water (~40% of body weight)
- ECF comprises about 1/3 of the total body water (~20% of body weight).
Body Water Distribution by Compartments
- Total body water is 42 liters in a 70kg male.
- Plasma is about 1/4 (10.5 Liters).
- Interstitial fluid, surrounds cells and tissues in connective tissue, bone, cartilage and is about 1/3 (14 liters).
- Intracellular fluid is about 2/3 (29.6 Liters)
Fluid Compartments
- Extra cellular fluid (ECF) and intracellular fluid (ICF)
Composition of Intracellular and Extracellular Fluids
- Extracellular fluid (ECF) contains large amounts of sodium, chloride, and bicarbonate ions.
- ECF also contains small quantities of potassium, calcium, magnesium, phosphate, and organic acid ions.
- Intracellular fluid (ICF) contains small amounts of sodium and chloride ions and almost no calcium ions.
- ICF contains significant amounts of potassium and phosphate ions, plus moderate quantities of magnesium and sulfate ions.
- Cells also have large amounts of protein content - almost four times more than plasma.
Composition of Body Fluids (in mmol/L)
- Provide tabulated data on cation and anion concentrations in Plasma, Interstitial, and Intracellular fluids.
Regulation of Total Body Water
- Ingestion and excretion of fluids and electrolytes affect total body water (TBW) and total body osmolarity (TBO).
- Fluid movement between compartments is affected by osmolarity and hydrostatic pressures.
Water Input and Output
- In healthy individuals, water intake equals water output.
- Exercise may cause water loss through sweat, needing more fluid intake.
Water Balance
- Water balance: Input = Output
- Dehydration is abnormal reduction in fluid volumes.
- Overhydration is abnormal increase in total body water.
Osmolarity
- Osmolarity is defined as the number of particles per liter of fluid (also known as osmolar concentration).
- Blood plasma osmolarity is approximately 286-300 mOsmoles/L.
- Hypoosmotic fluids have a lower osmolarity than plasma, and hyperosmotic fluids have a higher osmolarity.
Significance of Osmolarity
- At the cellular level, fluid balance between intracellular fluid (ICF) and extracellular fluid (ECF) is dependent on osmolarity.
- Intravenous fluids need to be isotonic with blood plasma to prevent cell shrinkage or swelling.
Significance of Osmolarity (Capillary Level)
- Plasma proteins exert oncotic pressure, drawing water from interstitial fluid into capillaries.
- Hydrostatic pressure from capillaries balances oncotic pressure.
Tonicity (of Solutions)
- Hypertonic solutions have a high solute concentration, low water concentration.
- Hypotonic solutions have low solute concentration, high water concentration.
- Isotonic solutions have equal solute and water concentrations.
Calculate the Osmolality
- Provide examples of calculations for calculating osmolality. (see relevant page 32 & 33)
Control of Water Balance
- Water intake is regulated by thirst.
- Water loss is regulated by antidiuretic hormone (ADH).
Regulation of Water Intake and Output
- Osmoreceptors in the hypothalamus detect changes in body fluid osmolarity.
- Changes in osmolarity lead to sensations of thirst, and fluid intake to restore balance.
Dehydration and Rehydration
- Summarize the process and mechanism of dehydration. Also, summarize rehydration.
Action of Antidiuretic Hormone (ADH)
- Summarize the roles of ADH and the feedback mechanisms associated with its action.
Starling Hypothesis
- Describes the forces driving fluid filtration across capillaries.
Hydrostatic Pressure
- Hydrostatic pressure is the pressure exerted by a fluid within a confined space.
- Hydrostatic pressure in capillaries forces fluid into the interstitial spaces.
Movement of Fluids Between Compartments
- Osmotic pressure exerted by plasma proteins prevents significant fluid loss from blood into interstitial spaces.
- Lymphatic system returns small amounts of excess protein and fluid to the circulation.
Hydrostatic and Colloid Osmotic Forces
- Four forces (Starling forces) determine fluid movement across capillary membranes.
- Capillary hydrostatic pressure, interstitial fluid pressure, capillary oncotic pressure, and interstitial oncotic pressure.
- These forces determine whether fluid flows in or out of the capillaries.
Starling Forces (summary of forces)
- The sum of these forces affects whether net filtration or absorption occurs.
Choosing the Correct Answers (multiple choice questions)
- Provide summaries of the correct answers to the multiple choice questions on pages 44 and 45 (for example).
Electrolyte Balance
- Sodium is the principal extracellular cation.
- Sodium salt osmolarity accounts for 90-95% of total osmolarity.
- Excretion regulated by aldosterone, ADH, ANP.
Sodium Homeostasis
- Regulated by atrial natriuretic peptide (ANP).
- ANP secretion occurs when blood pressure is high.
- ANP inhibits ADH and Renin secretion, and inhibits sodium and water reabsorption.
- Leads to more sodium and water excretion, decreasing blood pressure.
Regulation by Other Hormones
- Estrogens mimic aldosterone actions, causing water retention during pregnancy and menstruation.
- Progesterone reduces sodium reabsorption, creating a diuretic effect.
- Glucocorticoids promote sodium reabsorption, contributing to edema.
Potassium Homeostasis
- Potassium homeostasis is linked to sodium.
- Aldosterone's role in regulating both sodium and potassium in addition
Test Your Knowledge (answers)
- Provide answers to the test your knowledge questions on page 46
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Description
Test your knowledge on body fluids and their crucial roles in human physiology. This quiz covers aspects such as body water percentages, distribution, and functions. Understand the implications of body fluid constancy and its relevance in clinical medicine.
