Body Fluids
Prepared by
Dr.Mohammed Sharique Ahmed Quadri
Assistant prof. Physiology
Al Maarefa College
1
OBJECTIVES
By the end of this lecture you should be able to
• Describe of body fluid compartments as intra-cellular
fluid (ICF) Extra-cellular fluid (ECF), interstitial fluid,
trans-cellular fluid and total body water.
• Describe the composition of each fluid compartment,
in terms of volume and ions and represent them in
graphic forms.
• Describe daily intake and output of water and
maintenance of water balance.
• Define osmolarity
• Define Isotonic, Hypotonic, Hypertonic
• Name the causes of ECF hyper tonicity and hypo
tonicity and its effects on body?
• List factors influencing fluid compartments.
• Physiology factor: age, sex, adipose tissue, etc.
Pathological factors: Dehydration, fluid infusion.
2
Total Body Water:
• 60% of body weight ( less in females )
• Total body water : approx. 42 lit in 70 Kg body wt
• Intracellular Fluid (Within body cells):
2/3 of TBW (40%of body wt.) 28 L in 70kg body
wt.
• Extracellular Fluid (Out side body cells) :
1/3 of TBW(20% of body wt.) 14L in 70 kg body
wt.
3
Minor
ECF compartment :
-Transcellular fluid
-Lymph
4
OTHER EXTRACELLULAR
COMPARTMENT
• There are other TWO Minor Extracellular fluid
compartments also:
1. Lymph
2. Transcellular fluid
5
Minor ECF Compartment (cont)
1. Lymph :
fluid returned from the interstitial fluid to plasma by
Lymphatic System.
2. Transcellular Fluid
• It is small fluid volume secreted by specific cells in
the body.
• Example :
• Cerebrospinal fluid (CSF)- it surrounds the Brain and
Spinal cord
• Intra ocular fluid - in the eye
• Synovial fluid – lubricating joints
• Pericardial fluid, Intra pleural fluid
6
Classification of Body Fluids
7
Variation in water levels
• Lean tissue have higher fluid content than fat
tissue
• Gender: males have more lean tissue hence
more body fluids
• Age: Lean tissue lost with the age hence body
fluid decreases with age
Lean tissue : Muscle tissue without fat
8
Barriers Separating Body-Fluid
Compartments
• Barrier between plasma and interstitial fluid
– Blood vessel walls
• Barrier between ECF and ICF
– Cellular plasma membranes
– Major differences between ECF and ICF
• Presence of cell proteins in ICF that cannot permeate
the cell membrane to leave the cells
• Unequal distribution of Na+ and K+ and their attendant
ions
9
Ionic Composition of the Major Body-Fluid
Compartments
10
Important Differences
Between ECF & ICF
INTRACELLULAR FLUID [ICF]
EXTRACELLULAR FLUID [ECF]
1. ICF has more protein
1. No protein in Interstitial Fluid.
Protein present in Plasma.
2. More Potassium ion
(145 mmol / l)
2. Less Potassium ion
(4 mmol / l)
3. Less Sodium ion
(10 mmol / l)
3. More Sodium ion
(145 mmol / l)
4. More Phosphate ion
4. More Chloride ion
11
Na+ and K+ Concentration In
ECF & ICF
Q. Why Na+ is more in ECF and K+ more in ICF?
Ans: It is due to the Na+- K+ ATPase pump which
pumps 3 Na+ outside the cell and 2 K+ inside
the cell.
12
Fluid Balance
• Two factors are regulated to maintain fluid
balance in the body
– ECF volume must be closely regulated to help
maintain blood pressure
• Maintaining salt balance is very important in long-term
regulation of ECF volume
– ECF osmolarity must be closely regulated to
prevent swelling or shrinking of cells
• Maintaining water balance is very important in
regulating ECF osmolarity
13
H2O Input and Output
• Input
• Drinking liquids
• Eating solid foods
• Metabolically
produced water
(oxidation of carbohydrate,
lipid, proteins)
• Output
– Insensible loss
• Lungs
• Nonsweating skin
– Sensible loss
• Sweating
• Feces
• Urine excretion
In order to maintain stable water balance, water
input must equal water output.
14
Daily Water Balance
15
ECF OSMOLARITY
 What is Osmolarity ?
• Osmolarity is the concentration of solute particles
dissolved in the fluid.
• Increased Osmolarity means higher concentration of
solute and less concentration of water.
ECF Osmolarity (cont)
• As Na+ is the main solute in ECF, it is responsible for
ECF Osmolarity.
• In ICF K+ is responsible for ICF Osmolarity.
• Normally ECF and ICF are ISOTONIC (having same
Osmolarity).
Extracellular Fluid Osmolarity
• Normally Osmolarity of ECF and ICF are the same
(they are isotonic).
 Why ?
• Because total concentration of Na+ and other
solutes in ECF is equal to total concentration of K+
and other solutes inside the cell.
 Remember Osmolarity of ECF-285 mmol/l (275-295)
Importance of regulating ECF
Osmolarity
 PROBLEM
 If there is water loss from the ECF , what will be its
effect?
Answer – ECF will become Hypertonic.
Hypertonic Extracellular Fluid
• Conditions of water loss
– Diarrhea
– Vomiting
– Sweating
– Less water intake.
• If ECF becomes hypertonic, water moves from inside
to outside of cell by osmosis (i.e. from ICF to ECF).
• As water leaves the cell – cell shrinks.
Clinical Application
• In mild Dehydration (loss of water) and mild hyper
tonicity :
– There is dry skin
– Dry tongue thirst
– Sunken eyes.
• In case of severe Hyper tonicity ( Hyper Osmolarity)
of ECF, it may affect BRAIN CELLS and BRAIN
FUNCTION --- person may become mentally
confused.
HYPOTONIC ECF
 PROBLEM
 What will happen if ECF becomes Hypotonic (that is
having less Osmolarity) ?
• Answer – When ECF becomes Hypotonic , water will
enter the cell, and cell will swell ( Get bigger).
 NOTE – Usually Hypo tonicity does not
occur because when we take more water,
we loose water in urine, but it can happen
in Abnormal conditions.
Hypotonic Extracellular Fluid(cont)
Clinical Application
• Renal failure: Patient can not pass urine , ECF will
become hypotonic .
• When ECF becomes hypotonic, water enters into the
cell by Osmosis and cells swells (increase in size).
• Swelling of BRAIN cells will cause Brain Dysfunction
E.g. – headache, vomiting, confusion, drowsiness and
coma. This is called WATER INTOXICATION.
ISOTONIC SOLUTIONS
 What will happen if we give Isotonic solution?
• Answer – If we give ISOTONIC SOLUTION like 0.9%
saline (Isotonic saline) intravenously, ECF will remain
ISOTONIC , there will be no net movement of water
into or out of the cells. Only ECF volume will
increase.
 NOTE – In case of Diarrhea, vomiting ,
Isotonic saline is given intravenously .
References
• Human physiology by Lauralee Sherwood,
seventh edition
• Text book physiology by Guyton &Hall,11th
edition
• Text book of physiology by Linda .s
contanzo,third edition
25