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Body Fluids

بسم الله الرحمن الرحيم

Dr.Mohammed Sharique Ahmed QuadriAssistant prof. Physiology

Al Maarefa College

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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.

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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.

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Minor ECF compartment :

-Transcellular fluid -Lymph

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OTHER EXTRACELLULAR COMPARTMENT

• There are other TWO Minor Extracellular fluid compartments also:

1. Lymph

2. Transcellular fluid

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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

Classification of Body Fluids

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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

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

Ionic Composition of the Major Body-Fluid Compartments

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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

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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.

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

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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.

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Daily Water Balance

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