MBBS1 PPP Body Fluid Compartments

Questions and Answers

What percentage of total body weight is attributed to blood volume?

15%

8% (correct)

10%

What is the approximate volume of plasma space in the body?

14 L

10.5 L

5.5 L

3.5 L (correct)

How much total body water (TBW) is present in an average adult body weight of 70 kg?

60 L

42 L (correct)

35 L

28 L

What is the volume of interstitial space in the body?

10.5 L Signup and view all the answers

Which compartment contains approximately 28 L of water in an average adult?

Intracellular space Signup and view all the answers

Which percentage represents the total body water as compared to body weight?

60% Signup and view all the answers

What is the estimated average water content of lean tissue per kilogram?

0.71 L Signup and view all the answers

Which fluid compartment accounts for approximately 15% of total body water?

Interstitial fluid Signup and view all the answers

What is the unit for measuring osmolarity?

Osmole per liter Signup and view all the answers

What does the term 'tonicity' refer to in the context of osmotic pressure?

The effect of a solution's osmolarity on cell volume across a membrane. Signup and view all the answers

Which solution is considered isotonic with plasma?

0.9% w/v NaCl Signup and view all the answers

Why is osmolarity of plasma important to control?

It controls plasma volume and can exert significant pressure across membranes. Signup and view all the answers

How many milliosmoles are there in 10 mmol/litre of CaCl2?

30 mosm/litre Signup and view all the answers

How is crystalline osmotic pressure primarily characterized?

By small diffusible ions in body fluids. Signup and view all the answers

What percentage of total body water (TBW) is attributed to interstitial space?

15% Signup and view all the answers

Which ions are considered the major contributors to osmolarity in body fluids?

Na+, Cl-, K+ Signup and view all the answers

What distinguishes the concentrations of Na+, K+, and Ca2+ in extracellular fluid (ECF) compared to intracellular fluid (ICF)?

They differ considerably, affecting cell function. Signup and view all the answers

Why must the osmolarity of intracellular fluid (ICF) and extracellular fluid (ECF) be equal?

To prevent cell shrinkage or swelling. Signup and view all the answers

What is the primary role of electrolytes in body fluids?

To maintain osmotic balance and membrane potential. Signup and view all the answers

Which of the following statements about body fluid constituents is false?

Dissolved gases are a major component of interstitial fluid. Signup and view all the answers

What is the approximate oncotic pressure exerted by proteins in the interstitial fluid?

25 mmHg Signup and view all the answers

What major ion is responsible for controlling blood volume in plasma?

Na+ Signup and view all the answers

Which ion has a higher concentration in intracellular fluid compared to extracellular fluid?

K+ Signup and view all the answers

What is the role of oncotic pressure in the capillaries?

To balance hydrostatic pressures Signup and view all the answers

Which of the following ions is NOT typically found at high concentrations in intracellular fluid?

Na+ Signup and view all the answers

Which factor predominantly influences the membrane potential and action potential in cells?

Relative concentrations of Na+ and K+ Signup and view all the answers

What characterizes the permeability of the capillary wall?

Permeable to both ions and water Signup and view all the answers

Which of the following statements about hydrostatic and oncotic pressures is correct?

Oncotic pressure helps to retain fluid within the vessel. Signup and view all the answers

What is the total quantity of plasma proteins per liter in the human body?

70g Signup and view all the answers

Which of the following plasma proteins is primarily responsible for maintaining oncotic pressure?

Albumin Signup and view all the answers

What is the approximate concentration of fibrinogen in plasma?

3 g/litre Signup and view all the answers

How many grams per liter are the concentrations of alpha, beta, and gamma globulins typically?

0.7-13 g/litre each Signup and view all the answers

What is the primary function of globulins in plasma?

Facilitating immune response Signup and view all the answers

What is the principle of the dilution method most commonly used for measuring body fluid compartments?

Concentration of a known substance Signup and view all the answers

What osmolarity of plasma is essential for fluid movement within the body?

300 mOsm/L Signup and view all the answers

What does the term “anaemia” refer to in regards to blood components?

A deficiency in red blood cells Signup and view all the answers

Study Notes

Body Fluid Compartments

Human body consists of three main fluid compartments: intracellular fluid (ICS), interstitial fluid, and plasma.
Total Body Water (TBW) comprises about 60% of body weight, approximately 42 L for an average adult weighing 70 kg.
Intracellular space: ~28 L, constituting 40% of TBW.
Extracellular space (ECS): ~14 L, divided into interstitial (~10.5 L) and plasma (~3.5 L).

Constituents of Body Fluids

Major constituents include electrolytes (Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, PO42-), proteins, gases, nutrients, and metabolites.
Electrolytes are critical for governing osmolarity and overall cellular function.

Ionic Composition

Na+, Cl-, and K+ are predominant ions influencing osmolarity in body fluids; concentrations differ greatly between extracellular and intracellular compartments.
Osmolarity must remain equal between ICF and ECF, critical for homeostasis and cell function.

Osmotic Pressure and Osmolarity

Osmolarity is determined by the total number of diffusible entities in solution, expressed as osmolality or osmolarity.
Plasma osmolarity typically around 290 mosmol/liter; regulates both plasma volume and intracellular fluid volume.
Isotonic solutions match plasma tonicity; for example, 0.9% NaCl is considered isotonic saline.

Crystalloid vs. Oncotic Pressure

Crystalloid osmotic pressure arises from small, diffusible ions; cell membranes are impermeant to ions, necessitating equal osmolarity inside and outside of cells.
Oncotic pressure, primarily due to plasma proteins, is essential for fluid transport across capillaries, with a typical oncotic pressure of ~25 mmHg.

Ionic Concentrations in Plasma vs. Intracellular Fluid

Plasma concentrations:
- [Na+] ~140 mmol/L
- [K+] ~4 mmol/L
- [Ca2+] ~2 mmol/L
Intracellular concentrations:
- [Na+] ~10 mmol/L
- [K+] ~120 mmol/L
- [Ca2+] ~100 nmol/L
Relative concentrations of K+, Na+, and Ca2+ are vital for maintaining membrane potential and enabling nerve and muscle function.

Plasma Proteins

Total protein content in plasma: ~70 g/L, major proteins include:
- Albumin (48 g/L) – crucial for oncotic pressure and nutrient transport.
- Globulins (α, β, γ) – involved in immune response and transportation.
- Fibrinogen (3 g/L) – plays a key role in blood clotting.

Learning Outcomes

Know fluid compartments and their volumes in adults.
Understand methods for measuring fluid volumes.
Identify key constituents and their concentrations in plasma, ECF, and ICF.
Comprehend the role of osmolarity in fluid movement and its regulatory functions.
Classify and describe the functions of plasma proteins.
Recognize normal ranges for red and white blood cell counts and hemoglobin levels, and define “anemia.”

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Description

This quiz explores the various body fluid compartments including intracellular, interstitial, and plasma. It also discusses the movement of nutrients, metabolites, and gases like O2 and CO2 within these compartments. Test your understanding of these essential concepts in physiology.