Kompartemen Cairan Tubuh

BODY FLUID
COMPARTEMENTS
(KOMPARTEMEN CAIRAN TUBUH)
Medical Faculty Of Andalas University

Padang
2
Intake = Output
Water Intake and Output
3
Fluid Compartments
• Water occupies 2 main fluid compartments
• Intracellular fluid (ICF) – about two thirds
by volume, contained in cells
• Extracellular fluid (ECF) :
– Plasma – the fluid portion of the blood
– Interstitial fluid (IF) – fluid in spaces between
cells
• Other ECF – lymph, cerebrospinal fluid,
eye humors, synovial fluid, serous fluid,
and gastrointestinal secretions
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Fluid Compartment
Total Body Water: varies with fat
ICF high in K and Mg; ECF high in

Na, Cl
 Plasma high in protein, but

interstitial fluid low in
protein
Smallest compartment (plasma) most

important 5
Composition of Body Fluids
• Water is the universal solvent
• Solutes are broadly classified into:
– Electrolytes – inorganic salts, all acids and
bases, and some proteins
– Nonelectrolytes – glucose, lipids, creatinine,
and urea
• Electrolytes have greater osmotic power
than nonelectrolytes
• Water moves according to osmotic
gradients
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Functions of Body Water
• Give structure to the body

• Medium / Participates in biological rxns
• Medium for transportation
• Lubricant
• Temp control (600 kcal / L perspiration)
The Volume and Distribution of
Total Body Water (TBW)
TBW = ~60% total body mass

Extracellular Fluid (ECF) Intracellular Fluid (ICF)
~1/3 TBW or 20% body mass ~2/3 TBW or 40% body mass
Interstitial
Fluid (~3/4 ECF)
cell membrane
10.5 L H20
28 L H20
capillary endothelium
Intravascular
Fluid (~1/4 ECF)
Plasma = ~3.5 L H20
Adapted from C.A. Burtis, ed., et. al. Tietz Textbook of Clinical Chemistry. 3rd ed. Philadelphia: WB Saunders 8
Company, 1999, pg 1096.
Extracellular and Intracellular
• Extracellular fluids are similar (except for
the high protein content of plasma)
– Sodium is the chief cation
– Chloride is the major anion
• Intracellular fluids have low sodium and
chloride
– Potassium is the chief cation
– Phosphate is the chief anion
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Extracellular and Intracellular
• Sodium and potassium concentrations in

extra- and intracellular fluids are nearly
opposites
• This reflects the activity of cellular ATP-
dependent sodium-potassium pumps
• Electrolytes determine the chemical and
physical reactions of fluids
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Mechanisms Controlling Fluid and
Electrolyte Movement
• Diffusion
– molecules move from high to low concentration
• Facilitated diffusion
– involves carrier molecules
• Active transport
– movement against concentration gradient
– requires energy
– E.g.: keeping Na out and K in the cells (requires ATP)
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Fluid Movement Among
Compartments
• Compartmental exchange is regulated by
osmotic and hydrostatic pressures
• Net leakage of fluid from the blood is
picked up by lymphatic vessels and
returned to the bloodstream
• Exchanges between interstitial and
intracellular fluids are complex due to the
selective permeability of the cellular
membranes
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Water Balance and ECF
Osmolality
• To remain properly hydrated, water intake

must equal water output
• Water intake sources
– Ingested fluid (60%) and solid food (30%)
– Metabolic water or water of oxidation (10%)
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Water Balance and ECF
Osmolality
• Water output
– Urine (60%) and feces (4%)
– Insensible losses (28%), sweat (8%)
• Increases in plasma osmolality trigger
thirst and release of antidiuretic hormone
(ADH)
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Regulation of Water Intake
• The hypothalamic thirst center is

stimulated:
– By a decline in plasma volume of 10%–15%
– By increases in plasma osmolality of 1–2%
– Via baroreceptor input, angiotensin II, and
other stimuli
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Regulation of Water Intake
• Thirst is quenched as soon as we begin to
drink water
• Feedback signals that inhibit the thirst
centers include:
– Moistening of the mucosa of the mouth and
throat
– Activation of stomach and intestinal stretch
receptors
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Regulation of Water Output
• Obligatory water losses include:
– Insensible water losses from lungs and skin
– Water that accompanies undigested food
residues in feces
• Obligatory water loss reflects the fact that:
– Kidneys excrete 900-1200 mOsm of solutes
to maintain blood homeostasis
– Urine solutes must be flushed out of the body
in water
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Influence and Regulation of ADH
• Low ADH levels produce dilute urine and
reduced volume of body fluids
• High ADH levels produce concentrated
urine
• Hypothalamic osmoreceptors trigger or
inhibit ADH release
• Factors that specifically trigger ADH
release include prolonged fever; excessive
sweating, vomiting, or diarrhea; severe
blood loss; and traumatic burns
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Electrolyte Balance
• Electrolytes are salts, acids, and bases,
but electrolyte balance usually refers only
to salt balance
• Salts are important for:
– Neuromuscular excitability
– Secretory activity
– Membrane permeability
– Controlling fluid movements
• Salts enter the body by ingestion and are
lost via perspiration, feces, and urine
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Electrolytes – The Ion Components Inside and
Outside the Cells Are Not the Same.
Electrolyte Symbol Reference range
(serum)
Potassium K+ 3.7-5.2 mEq/L
Magnesium Mg2+ 1.8-2.4 mg/dL
ICF
Phosphate PO4- 4.5-6.0 mg/dL ( 11 yrs)
3.0-4.5 mg/dL ( 12 yrs)
Sodium Na+ 136-145 mEq/L
Chloride Cl- 98-108 mEq/L
ECF Bicarbonate HCO3- 22-32 mEq/L
Calcium Ca2+ 8.9-10.2 mg/L
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Adapted from Sara Duesterhoeft’s lecture, 2002.
Sodium in Fluid and Electrolyte
Balance
• Sodium holds a central position in fluid and
electrolyte balance
• Sodium salts:
– Account for 90-95% of all solutes in the ECF
– Contribute 280 mOsm of the total 300 mOsm
ECF solute concentration
• Sodium is the single most abundant cation in
the ECF
• Sodium is the only cation exerting significant
osmotic pressure
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Disorders of Water Balance:
Dehydration
• Water loss exceeds water intake and the
body is in negative fluid balance
• Causes include: hemorrhage, severe
burns, prolonged vomiting or diarrhea,
profuse sweating, and diuretic abuse
• Signs and symptoms:thirst, dry flushed
skin, and oliguria
• Other consequences include hypovolemic
shock and loss of electrolytes
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Dehydration
1 Excessive loss of H2O from 2 ECF osmotic 3 Cells lose H2O

ECF pressure rises to ECF by
osmosis; cells
shrink
(a) Mechanism of dehydration

24
Hypotonic Hydration
• Amount of water ingested quickly can lead

to cellular overhydration or water
intoxication
• ECF is diluted – sodium content is normal
but excess water is present
• The resulting hyponatremia promotes net
osmosis into tissue cells, causing swelling
25
Hypotonic Hydration
1 2 ECF osmotic 3 H2O moves into

Excessive H2O enters
the ECF pressure falls cells by osmosis;
cells swell
(b) Mechanism of hypotonic hydration

26
Sources
1. Beaudoin, D. Electrolytes and ion sensitive

electrodes. PPT. 2003.
2. Ivkovic, A ., Dave, R. Renal review. PPT
3. Kersten. Fluid and electrolytes. PPT.
4. Marieb, EN. Fluid, electrolyte, and acid-base
balance. PPT. Pearson Education, Inc. 2004
27

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BODY FLUID

Medical Faculty Of Andalas University

ICF high in K and Mg; ECF high in

 Plasma high in protein, but

Smallest compartment (plasma) most

• Give structure to the body

TBW = ~60% total body mass

• Sodium and potassium concentrations in

• To remain properly hydrated, water intake

• The hypothalamic thirst center is

1 Excessive loss of H2O from 2 ECF osmotic 3 Cells lose H2O

(a) Mechanism of dehydration

• Amount of water ingested quickly can lead

1 2 ECF osmotic 3 H2O moves into

(b) Mechanism of hypotonic hydration

1. Beaudoin, D. Electrolytes and ion sensitive

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