Body maintains a balance between the amount of fluid taken in and amount excreted. Fluid balance is the balance between water coming into the body, from drinks, food and water leaving the body, mainly in the form of urine.

1. BODY FLUIDS, ITS BALANCE
& MECHANISMS
Ms. AMANJOT KAUR SIDHU
MSN (CCN)

2. BODY FLUIDS
•Body maintains a balance between the amount
of fluid taken in and amount excreted.
•Fluid balance is the balance between water
coming into the body, from drinks, food and
water leaving the body, mainly in the form of
urine.

3. FLUID COMPARTMENTS
• Intracellular fluid (ICF): ICF refers to the fluids those
are located inside the cells. ICF contains large amount
of potassium, magnesium and phosphate ions.
• Extracellular fluid (ECF): ECF refers to the fluid outside
the cells. ECF contains large amount of sodium,
chloride and bicarbonate ions and substances needed
for cellular function such as oxygen, glucose, fatty
acids and amino acids.

4. Contd…
•Types of ECF:
•Interstitial fluid
•Intravascular fluid
•Transcellular fluid

5. FLUID PRESSURE
• Body fluids shift between the interstitial space and
intravascular space in the capillary as a result of differences
in the hydrostatic pressure and oncotic pressure.
• Hydrostatic pressure: It is the pressure caused by water
volume in the vessels.
• Oncotic pressure: It is the pressure exerted by plasma
proteins.

6. REGULATION OF FLUID BALANCE
HYPOVOLEMIA
Decreased fluid and blood volume
Stimulation of osmoreceptors in hypothalamus
ADH
THIRST ALDOSTERONE
Activation of RAAS which
contributes to decreased
urination & increase in BP.

7. NEGATIVE FEEDBACK MECHANISM
HYPERVOLEMIA
Increased fluid and blood volume
Causes stretching of right atrium that stimulates the release of ANP
That decreases the level of ADH and renin and increases the loss of
fluid from the body in the urine

8. MOVEMENT OF BODY FLUIDS
• Sodium-potassium pump: It continually pumps 3
sodium ions out of the cell and 2 potassium ions into
the cell by ATP.
• Diffusion: It is the movement of particles from a
region of higher concentration to the region of lower
concentration.
• Osmosis: It is the movement of water from an area of
lower concentration to an area of higher
concentration through semi-permeable membrane.