Body Fluid Compartments | ICF | ECF | General Physiology

Summary

This video explains the different body fluid compartments in the human body, which is composed of 50-70% water. It discusses the intracellular fluid (ICF) and extracellular fluid (ECF), separated by cell membranes, with two-thirds of the water inside cells and one-third outside. The ECF is further divided into plasma and interstitial fluid. The video also highlights solutes and proteins in these compartments, the role of osmolarity, and how water movement between compartments maintains balance. The indicator-dilution principle is introduced to measure fluid volumes in the body.

Takeaways

• 💧 The human body is composed of 50-70% water, with variations based on factors like age and body fat percentage.
• 🔄 Body water is distributed between intracellular fluid (ICF) inside cells and extracellular fluid (ECF) outside cells.
• 🧫 Two-thirds of the body's water is in the ICF, while one-third is in the ECF.
• ⚖️ In an average body, 60% of the body weight is water: 40% is ICF and 20% is ECF (60-40-20 rule).
• 🩸 The ECF is divided into plasma (inside vessels) and interstitial fluid (outside vessels), with interstitial fluid making up three-quarters of the ECF.
• 💡 Plasma and interstitial fluid are separated by the capillary membrane, while ICF and ECF are separated by the cell membrane.
• 🔬 The major cation in the ECF is sodium, while the major cations in the ICF are potassium and magnesium.
• ⚗️ Proteins are present in plasma and ICF, but the interstitial fluid contains very little protein due to the capillary membrane.
• 📏 Body water compartments can be measured using the indicator-dilution principle, with different indicators used for total body water, ECF, and plasma volume.
• 🔄 Osmosis maintains equilibrium between the ICF and ECF, as water moves across the cell membrane in response to solute concentration differences.

Q & A

What percentage of the human body is composed of water?

The human body is composed of 50 to 70 percent water, depending on factors like age and body fat percentage.

How is total body water distributed in the body?

Total body water is distributed inside the cells (intracellular fluid or ICF) and outside the cells (extracellular fluid or ECF).

What separates the intracellular fluid (ICF) and extracellular fluid (ECF)?

The cell membrane separates the intracellular fluid (ICF) from the extracellular fluid (ECF).

What fraction of total body water is intracellular fluid (ICF) and extracellular fluid (ECF)?

Two-thirds of total body water is intracellular fluid (ICF), and the remaining one-third is extracellular fluid (ECF).

How is extracellular fluid (ECF) further divided?

Extracellular fluid is divided into plasma (inside vessels) and interstitial fluid (outside vessels).

What is the main difference between plasma and interstitial fluid in terms of composition?

Plasma contains more proteins, which are too large to pass through the capillary membrane, while the interstitial fluid has very little protein.

What are the predominant cations and anions in the extracellular fluid (ECF)?

The predominant cation in the ECF is sodium, and the predominant anions are chloride and bicarbonate.

What are the major cations and anions in the intracellular fluid (ICF)?

The major cations in the ICF are potassium and magnesium, and the major anions are organic phosphates and proteins.

What principle is used to measure total body water, extracellular fluid, and plasma volume?

The indicator-dilution principle is used, where an indicator is placed in the compartment and its dilution is measured.

How does the movement of water between compartments help maintain osmotic balance?

Water moves across the semi-permeable cell membrane by osmosis to ensure that the osmolarity of the ECF and ICF remains equal.