body fluid compartments

1. BODY FLUID COMPARTMENTS
Dr Anu Priya J

2. Introduction
• Body is formed of solids & fluids
• The fluid part is more than 2/3 of the
whole body.
• Water forms most of the fluid part

3. 40%
15%
20%
5%
Total Body water
Blood volume 7% of body weight
5L in a 70 kg adult male

6. ECF constitutes of:
A. Interstitial fluid including
lymph
B. Plasma
C. Transcellular fluids
Transcellular fluids:
 CSF
 Intraocular fluid
 Gastrointestinal secretions
 Pleural fluid
 Pericardial fluid
 Peritoneal fluid
 Synovial fluid
 Fluid in urinary tract
More the amount of fat, lesser the ECF volume
Elderly – lesser ECF volume
Infants & children – greater ECF volume

7. Body electrolytes
• 7% of total body weight
• Functions of electrolytes in the human body
− Maintenance of acid-base balance
− Maintenance of normal osmolality and
volume of body fluids
− Ions like Na+,Ca2+,K+,Cl- , etc affects
excitability of cells

10. Distribution of ions across
the cell membrane at rest
Ion ICF (mmol/L of H20) ECF(mmol/L of H20)
Na+ 1.5 150
K+ 150 5.5
Cl- 9 125
Ca2+ 0.0001 1.2
Protein anion 65 <5
Mg2+ 58 3
HCO3- 10 2.8
PO4
3- 75 4

11. Deuterium oxide/heavy water, Tritium oxide, Aminopyrine
Inulin, Mannitol, Sucrose
131I

12. Applied aspect
Infants are prone to dehydration i.e.,
infants are more vulnerable for water loss due to:
• Absolute ECF volume is lesser
• Increased body surface area compared to mass
• Higher metabolic rate
• Physiologic inability of the infant’s kidneys to
concentrate urine
see http://www.ihrdni.org/068b-022.pdf

13. Thank you

14. Measurement of body fluid volumes
• Total body water is measured using dilution
principle.
• A marker is injected that will be evenly distributed in
all the compartments of body fluids.
• Marker that diffuses freely not only in the water
outside the cells, but also crosses the cell membrane
to reach the intracellular fluid.

15. • ECF volume is measured using substances that
cannot enter the cells, but can freely cross the
capillary membrane and thus distribute evenly in the
ECF compartments.
• Plasma volume is measured using substances that
binds specifically to plasma proteins, and will not
diffuse into the interstitium.
Measurement of body fluid volumes

16. http://www.ihrdni.org/068b-022.pdf