Body Fluids Dr.Mohammed Sharique Ahmed Quadri Assistant prof. Physiology Al Maarefa College.

Body Fluids

بسم الله الرحمن الرحيم

Dr.Mohammed Sharique Ahmed QuadriAssistant prof. Physiology

Al Maarefa College

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.

HUMAN BODY COMPOSITION

Human Body Composition:

Water ---- 60%

Protein --- 18%

Fat -------- 15%

Mineral --- 07 %

BODY WATER

• Body water makes 60% of body weight.

• Therefore body water is about 42 liters in 70 kg person.

• Body water is distributed between TWO major compartments:1. INTRACELLULAR FLUID (ICF)2. EXTRACELLULAR FLUID (ECF)

BODY WATER DISTRIBUTIONWe will see how this 42 liters of water is distributedbetween ICF and ECF • 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.

( ECF IS DIVIDED INTO INTERSTITIAL FLUID AND PLASMA ).

EXTRA CELLULAR FLUID

• Extracellular fluid (ECF)- 14 lit is divided into: - Interstitial fluid --- 11 liters - Plasma -------------- 3 liters

Note-- Interstitial fluid is the fluid which is distributed between the cells or surrounding the cells.

Plasma – It is fluid portion of blood.

Minor ECF compartment :

-Transcellular fluid -Lymph

OTHER EXTRACELLULAR COMPARTMENT

• There are other TWO Minor Extracellular fluid compartments also:

1. Lymph

2. Transcellular fluid

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

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

Extracellular Fluid[Plasma & Interstitial Fluid]

• Water and electrolyte are freely exchanged between plasma and interstitial fluid passively through pores of thin capillary membrane.

• But Plasma protein can not pass from plasma to interstitial fluid.

• Therefore plasma and interstitial fluid are nearly same in composition except that plasma has protein and interstitial fluid doesn’t have protein.

Extracellular Fluid [ECF] &

Intracellular Fluid [ICF]

Extracellular Fluid [ECF] & Intracellular Fluid [ICF]

• ECF and ICF are separated by plasma membrane.

• Plasma membrane is selectively permeable.

• There is passive transport and active transport occurring through the plasma membrane.

• There is difference between ECF and ICF.

Ionic Composition of the Major Body-Fluid Compartments

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

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.

‘Important Things To Remember’

• Both Interstitial Fluid and Plasma have same composition except that Plasma has more protein.

• ICF and ECF are different as plasma membrane is selectively permeable and Na+ - K+ ATPase pump is operating.

‘Important Things To Remember’

• ECF

Na+ 140 mmol / l (135-145 mmol / l) K+ 4 mmol / l (3.5 – 5 mmol / l) Cl- 105 mmol / l (100 – 110 mmol / l)

Fluid Balance

• In order to maintain stable water balance, water INPUT must equal water OUTPUT.

H2O Input and Output

• Input• Drinking liquids

• Eating solid foods

• Metabolically produced water

(oxidation of carbohydrate, lipid, proteins)

• Output – Insensible loss• Lungs• Evaporation from

skin– Sensible loss• Sweating• Feces• Urine excretion

Daily Water Balance

Fluid Balance

• Fluid Balance is regulated by: 1- ECF Volume

2- ECF Osmolarity

- ECF volume helps to maintain blood pressure and will be discussed later with blood pressure.

We will discuss ECF Osmolarity.

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