1. The normal composition of body fluids consists of 55% fluids and 45% solids in males, and 60% fluids and 40% solids in females. Total body water is divided into intracellular fluid (ICF) and extracellular fluid (ECF). 2. ECF contains plasma, interstitial fluid, and transcellular fluids such as lymph and cerebrospinal fluid. ICF volume is about 28L and ECF volume is about 14L in adults. 3. Fluid volumes are regulated through osmosis driven by electrolyte concentrations between compartments. Imbalances can cause conditions such as edema. Hormones and renal control maintain fluid homeostasis.

1. NORMAL COMPOSITION OF
BODY FLUID
Ginus Partadiredja
Department of Physiology

2. Total Body Mass
Female Male
45%
Solids
40%
Solids
55%
Fluids
60%
Fluids
2/3 ICF
1/3 ECF
ICF = Intra cellular fluid
ECF = Extra cellular fluid
80%
20%
Interstitial
fluid
Plasma

3. ICF = 40% BW
= 28 L
Interstitial Fluid
= 15% BW = 11 L
Plasma
= 5% BW = 3 L
ECF = 20% BW = 14 L

4. ECF: - Plasma
- Interstitial fluid
- Transcellular fluid (1-2 L):
- Lymph - Aqueous humor & vitreous body
- Cerebrospinal fluid - Endolymph, Perilymph
- Synovial fluid - Pleural, pericardial,
peritoneal fluids
Hematocrit: the fraction of blood composed of erythrocytes
- 0.40 (female)
- 0.36 (male)

5. Measurement of Fluid Volumes
indicator mass A = indicator mass B
volume A x concentration A = volume B x concentration B
Volume B = Volume A x Concentration A
Concentration B
A (mass in syringe) B (mass in blood)

6. Volume Indicators
Total body water 3H2O (tritium/ radioactive water), 2H2O
(deuterium/ heavy water), antipyrine
Extracellular fluid 22Na, 125I-iothalamate, thiosulfate, inulin
Intracellular fluid Total body water – extracellular fluid
volume
Plasma volume 125I-albumin, Evans blue dye (T-1824)
Blood volume 51Cr-labeled erythrocytes, or
Blood volume = Plasma volume/(1 – Ht)
Interstitial fluid Extracellular fluid volume – plasma
volume
Measurement of Body Fluid Volumes

7. Sources of Body Fluid (input & output)
2500
2000
1500
1000
500
0
Drink
1600 ml
Kidney
1500 ml
Metabolic 200 ml
Food
700 ml Skin 600 ml
Lung 300 ml
GIT 100 ml
• Metabolic  Cellular aerobic respiration (production of ATP)
 Dehydration sinthesis
(glucose + fructose  sucrose + H2O)
Input
Output

8. • Insensible water loss (skin + lung) = 700 ml
• Skin = 200 ml (sweat) + 400 ml (insensible water loss)
• Insensible water loss via lungs = 300 – 400 ml
• 47 mmHg (vapour pressure in lung)
• cold weather  vapour pressure = 0 mmHg

9. The Concentration of Electrolytes & Anion Protein in
Plasma, Interstitial and Intracellular Fluid
mEq/L
175
150
125
100
75
50
25
0
Na+ K+ Ca+2 Mg+2 Cl- HCO3
- HPO4
2- SO4
2- Anion
Protein
Plasma
Interstitial fluid
Intracellular fluid
142 145
10
4 4
140
5 3 0.2
2 2 35
100 117 3
24 27 15
2 2 100
1 1 20
20 2 50

10. • Interstitial fluid  plasma, except proteins
• Interstitial fluids >< plasma  proteins  plasma colloid
osmotic pressure
• Cell membrane  permeable to water, but not to ions
• Extra cellular fluid: Na+ & Cl-
• Intra cellular fluid: K+, protein, HPO4
2-

11. • The functions of ions of electrolytes:
1.Control of water osmosis
2.Acid – base balance (H+, HCO3
-)
3.Current flows (Na+, K+, Cl-, Ca+2)  action potential (in
neurons)
4. Enzyme cofactors (Mg)

12. • Natrium/ Sodium
- Affects ½ ECF osmolarity (142 mOsm/L of 300 mOsm/L)
- Aldosteron  Na+ reabsorption increases
- Hyponatremia  ADH  water excretion increases
- ANP hormone  Na+ excretion increases
- Renal failure  Na+ retention  blood volume ,
- Hyperaldosteronism (hypernatremia) edema
- Adrenal insufficiency  aldosteron
- Diuretics  Na+ excretion  hypovolemia,
- Diarrhea, vomiting  hyponatremia

13. • Chloride
- Easy to move in/ out between ECF & ICF
- Important for anion balance (in erythrocytes)
O2 + HbH  HbO2 + H+
H+ + HbO2  HbH + O2

14. • Kalium/ Potassium
- Resting membrane potential & repolarization
- Aldosterone  K+ secretion
• Bicarbonate (HCO3
-)
- Kidneys: main regulator of HCO3
-
• Calcium
- 98%  skeleton & teeth
- Blood clotting, neurotransmitter, muscle tone, nerve &
muscle excitability
- Parathyroid & calcitriol hormones  Ca2+

15. - Ca2+ plasma  PTH  stimulating osteoclasts
releases Ca2+  blood (resorption )
Ca2+ reabsorption (kidneys)
Calcitriol  Ca2+ absorption (GIT)

17. • Phosphate (H2PO4
-, HPO4
2-, PO4
3-)
- 85% calcium phosphate (bones)
- HPO4
2-  buffer H+, organic molecule, nucleic acids, ATP
- PTH  HPO4
2- resorption  blood
 inhibition of HPO4
2- reabsorption
- Calcitriol  phosphate & Ca+2 absorption
• Magnesium
- Enzymes cofactor
- Na+ – K+ pumps
- Neuromuscular activities
- Synapse transmission
- Myocardial function

18. Fluid and electrolytes exchange:
- Filtration - Diffusion
- Reabsorption - Osmosis

19. • Diffusion: the process by which a gas or a substance in
solution (solutes) expands

20. • Osmosis: - the diffusion of solvent
- the net diffusion of water across a selectively permeable
membrane from a region of high water concentration (low
solute concentration) to one that has a lower water
concentration (high solute concentration)

21. Basic Principles of Osmosis and Osmotic Pressure
• Mole (mol)  gram-molecular weight of a substance (g)
• 1 mol NaCl = 23 g + 35.5 g = 58.5 g
• Osmole  the number of osmotically active particles in a
solution
• 1 mol/L glucose = 1 osm/L
• 1 mol/L NaCl = 2 osm/L
• 1 mol/L Na2SO4 = 3 osm/L
• Osmolality  concentration expressed as osmoles per kg
of water
• Osmolarity  concentration expressed as osmoles per L of
solution (clinically more frequently used)
• Osmotic pressure: the pressure required to prevent
osmosis

22. • Osmotic pressure  proportional to osmolarity, regardless
large or small molecules
• Osmotic effect of albumin (MW = 70,000) = glucose (MW =
180) < NaCl (2x of glucose or albumin)
• van’t Hoff’s law of osmotic pressure:  = CRT
• C = concentration of solutes in osmoles/ L
• R = ideal gas constant
• T = normal body temperature (273° + 37° = 310° kelvin)
•  = 1 mOsm/L x R x 310°K = 19.3 mmHg

23. Osmotic pressure of 0.9% NaCl (infusion solution)
0.9% = 0.9 g/ 100 mL = 9 g/ 1 L
MW NaCl = 58.5 g/mol
The molarity of 0.9% NaCl = 9 : 58.5 = 0.154 mol/ L
1 mol/ L of NaCl = 2 osm/ L  0.154 x 2 = 0.308 osm/ L
= 308 mOsm/ L
The potential osmotic pressure = 308 x 19.3 = 5944 mmHg
Osmotic coefficient of NaCl = 0.93
308 x 0.93 = 286 mOsm/ L
308 mOsm/ L or 286 mOsm/ L  close to ± 300 mOsm/ L
(plasma osmolarity)

24. Plasma
(mOsm/L H2O)
Interstitial
(mOsm/L H2O)
Intracellular
(mOsm/L H2O)
Na+
142 139 14
K 4.2 4.0 140
Ca 1.3 1.2 0
Mg 0.8 0.7 20
Cl 108 108 4
HCO 24 28.3 10
HPO, HPO 2 2 11
SO 0.5 0.5 1
Phosphocreatine 45
Carnosine 14
Amino acids 2 2 8
Creatine 0.2 0.2 9
Osmolar Substances in ECF and ICF

25. Plasma
(mOsm/L H2O)
Interstitial
(mOsm/L H2O)
Intracellular
(mOsm/L H2O)
Lactate 1.2 1.2 1.5
ATP 5
Hexose
monophosphate
3.7
Glucose 5.6 5.6
Protein 1.2 0.2 4
Urea 4 4 4
Others 4.8 3.9 10
Total mOsm/ L 301.8 300.8 301.2
Corrected
osmolar activity
282.0 281.0 281.0
Total osmotic
pressure at 37°C
(mm Hg)
5443 5423 5423

26. • Isotonic fluid: a solution of impermeant solutes with an
osmolarity of 282 mOsm/ L (e.g. 0.9% NaCl; 5% glucose)
• Hypotonic fluid: osmolarity < 282 mOsm/ L
• Hypertonic fluid: osmolarity > 282 mOsm/ L

27.  Isosmotic fluid: a solution with the same osmolarity with
cells, regardless the solute can penetrate the cell
membrane
 Hypo-osmotic fluid: lower osmolarity
 Hyper-osmotic fluid: higher osmolarity

28. Dehydration
Saliva Blood volume
Blood osmolarity
Mouth & pharynx
dryness
Stimulation of osmoreceptor
(hypothalamus)
Blood pressure
Renin production by
juxtaglomeral cells
in kidneys
Angiotensin II
Stimulation of thirst centre
(hypothalamus)
Thirst Drink Body fluid
Fluid Intake Regulation

29. • Body fluid osmolarity  ADH  protein aquoporin 2 
cell apical membrane  permeability to water  osmosis
to blood
• Blood volume
• Dehydration
• Hiperventilation
• Vomitus ADH
• Diarrhea
• Fever
• Heavy sweating
• Combustio (burn)  up to 3 – 5 L/ day

30. • Water exchange between body compartments
• Water loss  replaced by plain water  ECF osmolarity
 ECF osmosis  ICF
• Too much plain water consumption  water intoxication
• Enema

31. NaCl intake
(80% of ECF
Osmolarity)
Na+ & Cl- plasma
concentration
Osmosis of water from ICF
 Interstitial  plasma
Blood volume
Strecthing the atrium of the heart Renin production
Atrial Natriuretic Peptide (ANP) Angiotensin II
GFR Aldosterone
Reabsorption of NaCl by kidneys
Na+ & Cl- via urine (Natriuresis)
Water loss in urine via osmosis Blood volume
Hormonal Regulation of Renal Na+ & Cl-

32. Age & Fluid Balance
Infant Adults
Proportion of water 75% - 90%
ECF > ICF (2x)
55% - 60%
ICF > ECF
(2x)
Input – output rate 7x >
Metabolic rate 2x >
The development of
kidneys
Infant ½ x adults efficiency
Ratio of body surface :
volume
3x >
Respiratory frequency 30 – 80x/ min
Ion concentration K+, Cl- >

33. • Elderly: - ICF volume decreases
- K+ decreases
- fat increases
• Elderly  vulnerable to:
- dehydration
- hypernatremia
- hyponatremia
- hypokalemia
- acidosis

34. Edema
• Edema: Excess fluid in the body tissues
• Edema:
- Intracellular edema
e.g. low blood supply  cell membrane ionic pumps
depressed  sodium retention in the cell  osmosis into
the cell  intracellular edema
- Extracellular edema
1. Abnormal leakage: plasma  interstitial spaces
2. Failure of lymphatic return into the blood

35. Causes of Extracellular Edema
1. Increased capillary pressure
A. Kidney retention of salt & water (kidney failure,
mineralocorticoid excess)
B. High venous pressure & venous constriction (heart
failure, venous obstruction, failure of venous pumps)
C. Decreased arteriolar resistance (excessive body
heat, vasodilator drugs, sympathetic insufficiency)
2. Decreased plasma proteins
A. Loss of proteins in urine (nephrotic syndrome)
B. Loss of proteins from skin (burns, wounds)
C.Failure to produce proteins (liver diseases,
malnutrition)

36. 3. Increased capillary permeability
A. Immune reactions
B. Toxins
C. Bacterial infections
D. Vitamin deficiency (vitamin C)
E. Prolonged ischemia
F. Burns
4. Blockage of lymph return
A. Cancer
B. Infections
C. Surgery
D. Congenital absence/ abnormality of lymph vessels

37. Safety Factors that Prevent Edema
1. Low tissue compliance in the negative pressure range
(safety factor = 3 mm Hg). Compliance = the change in
volume per milimeter of mercury pressure change)
2. Increased lymph flow  10 – 50x (safety factor = 7 mm Hg)
3. Washdown of proteins from the interstitial spaces (safety
factor = 7 mm Hg).
Marked edema occurs if capillary pressure rise by 17 mm Hg
Effusion = edema fluid in the potential spaces (pleural cavity,
peritoneal cavity, pericardial cavity, synovial cavity). E.g.
ascites

38. • References:
1. Tortora GJ & Derickson B (2006). Principles of Anatomy &
Physiology, Chapter 27: Fluid, Electrolyte, and Acid-Base
Homeostasis
2. Ganong WF (2005). Review of Medical Physiology, 22nd
ed. Chapter 1: The General & Cellular Basis of Medical
Physiology, Pages 1–8; Chapter 39: Regulation of
Extracellular Fluid Composition & Volume, Pages 729-730
3. Gutyon AC & Hall JE (2006). Textbook of Medical
Physiology, 11th ed. Chapter 25: The Body Fluid
Compartments: Extracellular and Intracellular Fluids;
Interstitial Fluids and Edema, Pages 291-306