Chapter 55.1 - Composition of body fluids

Question 1

Total body water is divided into :

Answer 1

2 main compartments:

1 - Intracellular fluid
2 - Extrcellular fluid

ECF volume is approximately 20 - 25% of body weight
ICF volume is approximately 30-40% of body weight.

Question 2

ECF is divided into?

Answer 2

1 - Plasma water
2 - Interstitial fluid

• Plasma water is 5% of body weight
• blood volume ( with a hematocrit of 40%) is usually 8% of body weight.
• Interstitial fluid is normally 15% of body weight

Question 3

electrolyte composition of ECF And ICF

Answer 3

ECF : Sodium and chloride is dominant
ICF: Potassium is most abundant cation
Proteins, organic anions and phophate are abundant anions in ICF

Question 4

Osmolality

Answer 4

Normal plasma osmolality is 2850295 mOsm/kg

The osmolality of ECF can be determined and it usually equals the ICF osmolality

Question 5

Formula to ESTIMATE plasma osmolality

Answer 5

osmola