38 Questions
What percentage of the body weight does the extracellular fluid account for in a 70-kilogram adult man?
20 percent
Approximately how much of the extracellular fluid is made up of interstitial fluid?
Three fourths
What is the primary difference in composition between the plasma and interstitial fluid?
Protein concentration
What is the approximate volume of the plasma in a 70-kilogram adult man?
3 liters
What percentage of the total body weight does the intracellular fluid constitute in an 'average' person?
40 percent
How many liters of fluid are in the intracellular fluid compartment in an 'average' person?
28 liters
What is the approximate volume of the transcellular fluids in the body?
1 to 2 liters
What factor does the percentage of total body weight depend on?
Age, gender, and degree of obesity
What is the primary regulator of water intake in the body?
Thirst center
What is the average amount of water lost through faeces in a healthy individual?
200 mL/day
What is the primary mechanism of water loss through sweat?
Evaporation from the skin
What is the approximate amount of water produced endogenously through the oxidation of foodstuffs?
300 mL/day
What is the term used to describe the loss of water from the body that is not consciously perceived?
Insensible loss
What is the primary factor that influences water intake in individuals living in hot climates?
Environmental conditions
What is the approximate amount of water eliminated from the body in urine?
1500 mL/day
What is the term used to describe the loss of water from the body through the production of sweat from the skin?
Water loss in sweat
What is the minimum daily requirement of water intake?
1 L
What is the primary cause of dehydration?
Insufficient fluid intake
What is the term for the presence of excess fluid in the body tissues?
Edema
What is a condition that can cause intracellular edema?
Hyponatremia
What happens to the cell membrane ionic pumps when blood flow to a tissue is decreased?
They become depressed
What is the result of depressed cell membrane ionic pumps in terms of sodium ions?
Sodium ions that normally leak into the interior of the cell can no longer be pumped out
Which of the following can cause intracellular edema?
Inflamed tissues
How much water intake is required daily for the most active individuals?
2 to 3 L
What is the result of increased cell membrane permeability during inflammation?
Sodium and other ions diffuse into the cell
What is the primary cause of extracellular fluid edema?
Increased capillary fluid filtration
What is an example of a condition that can lead to lymphedema?
Congenital absence of lymphatic vessels
What is the main consequence of excessive capillary fluid filtration?
Interstitial fluid accumulation
What percentage of body weight is the total body water?
60 percent
What is a common clinical cause of interstitial fluid accumulation?
All of the above
What is the term used to describe the failure of the lymphatics to return fluid from the interstitium back into the blood?
Lymphedema
What is the primary function of maintaining a constant volume and composition of body fluids?
Homeostasis
What are the two main compartments of body fluid?
Intracellular and extracellular fluids
What is the approximate volume of total body water?
42 liters
What is the term for fluids outside the cells?
Extracellular fluid
What is included in the transcellular fluid compartment?
All of the above
Why is it remarkable to maintain a constant volume and composition of body fluids?
Because of the continuous exchange of fluid and solutes with the external environment
What are the clinical implications of abnormalities in the control systems that maintain the relative constancy of the body fluids?
Some of the most common and important problems in clinical medicine
Study Notes
Body Fluid Compartments
- The body fluid is divided into two main compartments: extracellular fluid (ECF) and intracellular fluid (ICF).
- The total body water (TBW) is approximately 60% of the body weight, which is around 42 liters in a 70-kilogram adult man.
Extracellular Fluid Compartment
- The extracellular fluid compartment accounts for about 20% of the body weight, which is around 14 liters in a 70-kilogram adult man.
- The ECF is divided into three main sub-compartments: interstitial fluid, plasma, and transcellular fluid.
- The interstitial fluid makes up more than three-fourths of the ECF, which is around 11 liters.
- The plasma makes up almost one-fourth of the ECF, which is around 3 liters.
- The transcellular fluid constitutes about 1-2 liters.
Intracellular Fluid Compartment
- The intracellular fluid compartment accounts for about 40% of the body weight, which is around 28 liters in a 70-kilogram adult man.
- The ICF is the fluid inside the 100 trillion cells of the body.
Water Input and Output
- Water is added to the body fluids through ingestion of water and food, as well as endogenous production of water during oxidation of foodstuffs.
- Water intake is highly variable and can range from 0.5 to 2.0 liters per day, depending on social and personal habits, and environmental conditions.
- Water output occurs through urine, faeces, sweat, and insensible loss.
- Insensible loss of water occurs by evaporation from the skin and respiratory passages, and can range from 100 mL/day to 5000 mL/day in hot weather.
- Water loss in faeces is around 200 mL/day in a healthy individual, but can increase tremendously in diarrhoea.
- Water loss in urine is around 1500 mL/day, but can be highly variable.
Dehydration
- Dehydration is defined as excessive loss of water from the body.
- The minimum daily requirement of water intake is around 1 liter, but can vary with age and activity level.
- Dehydration occurs when fluid loss is more than what is consumed.
Edema
- Edema refers to the presence of excess fluid in the body tissues.
- Edema can occur in both intracellular and extracellular fluid compartments.
- Intracellular edema can occur due to hyponatremia, depression of the metabolic systems of the tissues, and lack of adequate nutrition to the cells.
- Extracellular edema can occur due to abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries, or failure of the lymphatics to return fluid from the interstitium back into the blood.
This lecture covers the different types of body fluid compartments, their percentages, and the distribution and functions of electrolytes. It also discusses fluid intake and output during steady state conditions.
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