1. What are Body
Fluids?
- Body
fluids are the liquid portion of our body.
- They help
in transport of nutrients, gases, hormones, and waste products.
- ~60% of
body weight in adults is water (body fluid).
2. Distribution of Body
Fluids
Let’s take a 70 kg person:
- Total Body
Water (TBW) = ~60% of body weight = ~42 liters
(Varies by age, sex, fat content)
TBW is divided into:
A. Intracellular Fluid (ICF)
- Fluid inside
the cells
- Makes up 2/3rd
of TBW ≈ 28 L
B. Extracellular Fluid (ECF)
- Fluid outside
the cells
- Makes up 1/3rd
of TBW ≈ 14 L
ECF is further divided into:
i. Interstitial Fluid (between
cells) – 10.5 L
ii. Plasma (fluid part of blood)
– 3.5 L
Mnemonic to remember fluid distribution:
“60 – 40 – 20 Rule”
|
% of body weight |
Fluid |
|
60% |
Total Body Water |
|
40% |
ICF |
|
20% |
ECF (15% IF + 5% Plasma) |
3. Composition of Body
Fluids
Intracellular Fluid (ICF):
- High in: K⁺,
Mg²⁺, PO₄³⁻ (phosphate), Proteins
- Low in:
Na⁺, Cl⁻, Ca²⁺
Mnemonic: “KMP inside the cell”
K⁺, Mg²⁺, Phosphate = high in ICF
Extracellular Fluid (ECF):
- High in: Na⁺,
Cl⁻, Ca²⁺, HCO₃⁻
- Low in:
K⁺, Mg²⁺, PO₄³⁻
Mnemonic: “Sodium Chloride is salty like EC Food”
ECF = Na⁺, Cl⁻ dominant
4. Functions of Body
Fluids
- Transport of
oxygen, nutrients, waste
- Maintains temperature
- Acts as solvent
for biochemical reactions
- Maintains blood
volume and pressure
- Helps in electrolyte
and acid-base balance
Mnemonic: “TOPES”
- T –
Transport
- O – Osmotic
balance
- P – pH
maintenance
- E –
Electrolyte balance
- S – Solvent
function
5. Regulation of Body
Fluids
Maintained by:
- Thirst
mechanism – hypothalamus
- Kidneys –
regulate water & electrolytes
- Hormones:
- ADH
(Vasopressin) – retains water
- Aldosterone –
retains Na⁺
- ANP –
excretes Na⁺ & water
Mnemonic: “A3 for Fluid Balance”
- ADH
- Aldosterone
- ANP
6. Abnormalities of
Body Fluid Volume
|
Condition |
Description |
|
Dehydration |
Water loss > intake |
|
Overhydration |
Water intake > loss |
|
Edema |
Excess fluid in interstitial space |
FAQs (Frequently Asked Questions)
Q1. What is the total
body water in a 70 kg adult?
Ans: Around 60% of body weight, i.e., ~42 liters.
Q2. What is the
difference between ICF and ECF?
Ans:
- ICF – fluid inside
cells (high K⁺, PO₄³⁻)
- ECF – fluid outside
cells (high Na⁺, Cl⁻)
Q3. What are the types
of ECF?
Ans:
- Interstitial
fluid
- Plasma
- (Also
includes lymph, CSF, synovial fluid, etc.)
Q4. Which hormone
increases water reabsorption?
Ans: ADH (Antidiuretic Hormone)
Q5. What happens in
dehydration?
Ans:
There is loss of body water, leading to symptoms like:
- Dry mouth
- Low BP
- Increased
heart rate
- Concentrated urine
