1.1. Body fluid compartments and their determination. The extracellular and intravascular fluid.

Question 1

1. Body fluid compartments and their determination
   a/ What are the fluid compartments we have?

Answer 1

Total body water is divided into 4 compartments:
- Intracellular fluid (green)
- Interstitial fluid (blue)
- Blood plasma (red)
- Transcellular water (E.g, synovial

Question 2

1. Body fluid compartments and their determination
   b/ What is the relationship between the volumes of various body fluid compartment?

Answer 2

1. Total body water (TBW) = 0.6 x body weight
2. ECF = 0.2 x body weight
3. Interstitial fluid = ¾ ECF
4. Blood plasma = ¼ ECF
5. ICF = 0.4 x body weight

Question 3

1. Body fluid compartments and their determination
   c/ How do we determine various fluid compartments?

Answer 3

By using dilution method
Volume(v) = mass (m)/ concentration (c)
- By measuring the volume of marker substances which are distributed in the body fluid compartment according to its physical characteristics.

Question 4

1. Body fluid compartments and their determination
   d/ Examples of marker substances in different compartments?

Answer 4

Marker substances in different fluid compartments
1. Total fluid compartment: deuterium (also known as heavy water)
- Substances are distributed wherever water is found

2. ECF: inulin
   - Substances are distributed throughout the ECF but does not cross the plasma membrane
3. Blood plasma: blood protein concentration/ blood bound dye (Evans-blue)

Question 5

The extracellular fluid (ECF) and intravascular fluid
a/ What is the relationship between the ECF to TBW?

Answer 5

ECF = 1/3 of TBW

Question 6

2. The extracellular fluid (ECF) and intravascular fluid
   b/ What are the fluid compartments of ECF? How are they separated?

Answer 6

• ECF includes intravascular fluid, interstitial fluid and transcellular fluid
• Capillary endothelium separates intravascular fluid from interstitial and transcellular fluid

Question 7

2. The extracellular fluid (ECF) and intravascular fluid
   c/ Characteristics and locations of transcellular fluid

Answer 7

Characteristics
- Transcellular fluid = 1L of TBW

Location
- CFF
- Ocular fluid
- Synovial joint fluid
- Fluid in pleural cavity
- Fluids in peritoneal cavity

Question 8

2. The extracellular fluid (ECF) and intravascular fluid
   d/ Characteristics of intravascular fluid

Answer 8

• Mixture of blood cells, proteins and ions
• Plasma = EC component

Question 9

2. The extracellular fluid (ECF) and intravascular fluid
   e/ Characteristics of interstitial fluid

Answer 9

It surrounds the cell externally

Question 10

3. Ionic composition of the extracellular fluid and intracellular fluids
   a/ Ionic composition of Na+ in ECF and ICF?

Answer 10

ECF: 135 - 147 mM
ICF: 10 - 15 mM

Question 11

3. Ionic composition of the extracellular fluid and intracellular fluids
   b/ Ionic composition of K+ in ECF and ICF?

Answer 11

ECF: 3.5 - 5.0 mM
ICF: 120 - 150 mM

Question 12

3. Ionic composition of the extracellular fluid and intracellular fluids
   c/ Ionic composition of Ca2+ in ECF and ICF?

Answer 12

ECF:
2,1 – 2,8 mM (total blood plasma)
1,1 – 1,4 mM (free)

ICF:
100 mM (free)

Question 13

3. Ionic composition of the extracellular fluid and intracellular fluids
   d/ Ionic composition of Cl- in ECF and ICF?

Answer 13

ECF: 95 - 105 mM
ICF: 20 - 30 mM

Question 14

3. Ionic composition of the extracellular fluid and intracellular fluids
   e/ Ionic composition of HCO3- in ECF and ICF?

Answer 14

ECF: 22 - 28 mM
ICF: 12 - 16 mM

Question 15

3. Ionic composition of the extracellular fluid and intracellular fluids
   e/ Ionic composition of HCO3- in ECF and ICF?

Answer 15

ECF: 22 - 28 mM
ICF: 12 - 16 mM

Question 16

3. Ionic composition of the extracellular fluid and intracellular fluids
   f/ Ionic composition of Osmolarity in ECF and ICF?

Answer 16

ECF: 290 mOsm
ICF: 290 mOsm

Question 17

3. Ionic composition of the extracellular fluid and intracellular fluids
   f/ pH in ECF and ICF?

Answer 17

ECF: 7.4
ICF: 7.2