Physiology

1. Composition
and Function of
Blood
Rashmi Priyem Saravanan

2. Composition of Blood
A. Total Blood Volume = 5 - 6 litres “8 % of Body Weight”
B. Specific Gravity = 1050 - 1060
C. Viscosity = 4 – 5 Times that of Water
D. pH = 7.4 +/- 0.05 “Alkaline”

3. If Anticoagulated Sample of Blood is
allowed to Stand in a Narrow Tube
“On Settling it Separates Out into Cells
and Plasma“

4. Cells
 The Cellular Elements of Blood Represents 45 % of the Total Blood Volume called “
Packed Cell Volume “ or “ Haematocrit ”
 Includes
 Erythrocytes or Red Blood Corpuscles (RBCs)
 Normal Count - 5 million / µL
 Leucocytes or White Blood Corpuscles (WBCs)
 Normal Count - 4000 – 11000 / µL
 Thrombocytes or Platelets
 Normal Count - 1.5 – 4 lacs / µL
 µL was Previously Called as Cumm

5. Plasma
 Clear , Straw Coloured Fluid Portion of the Blood
 Represents 55 % of the Total Blood Volume “ 5% of Body Weight ”
 Contains
 91 % Water
 9 % Solids
 1 % Inorganic Molecules
 8 % Organic Molecules

6. Plasma
A. Major Inorganic Molecules :
A. Na ion , Ca ion , Cl ion , Bicarbonate ion ( mainly Extracellular )
B. K ion , Mg ion , Cu ion , Phosphate ion , Protein ion ( mainly Intracellular )
C. Fe – Cuprous and Cupric Ion
B. Major Organic Molecules :
A. 7 % are Plasma Proteins
B. 1 % are Non - Protein Nitrogenous Substances , Sugars , Fats , Enzymes and
Hormones

7. Plasma Proteins
Normal Value – 6.4 -8.3 gm/dL

8. Plasma Proteins - Components
1. 55 % Albumin : 3 – 5 gm/dL (Avg – 4.8 gm/dL)
2. 38% Globulin : 2 – 3 gm/dL (Avg – 2.3 gm/dL)
1. 13 % α-Globulin = 0.78 – 0.81 gm/dL
2. 14 % β-Globulin = 0.79 – 0.84 gm/dL
3. 11 % γ-Globulin = 0.66 – 0.70 gm/dL
4. A/G Ratio = Albumin : Globulin : : 1.7 : 1
3. 7 % Fibrinogen : 0.3 gm/dL
4. Prothrombin : 40 mg/dL

9. Non-Protein Nitrogenous
(NPN) Substances
Normal Value – 28 – 40 mg/dL

10. Non-Protein Nitrogenous Subs. -
Components
1. Urea : 20 – 40 mg/dL
2. Uric Acid : 2 – 4 mg/dL
3. Creatine : 1 – 2 mg/dL
4. Creatinine : 0.6 – 1.2 mg/dL
5. Xanthine : Traces
6. Hypoxanthine : Traces

11. Other Substances
 Neutral Fats (Triglycerides) : 30 – 150 mg/dL
 Phospholipids(Lecithin , Sphingomyelin , Cephalin) : 150 – 300 mg/dL
 Glucose (Fasting) : 70 – 90 mg/dL
 Cholesterol : 120 – 200 mg/dL

12. Functions of Blood
 Respiratory Function
 Blood transports
 Oxygen from Lungs to Tissues
 Carbon-dioxide from Tissues to Lungs

13. Functions of Blood
 Nutritive Function
 Blood conveys absorbed Food Materials , Glucose , Amino Acids , Fatty Acids ,
Vitamins , Electrolytes and Trace Metals
 From the Alimentary Canal to the Tissues
 For Utilisation and Storage

14. Functions of Blood
 Excretory Function
 Blood transports the Metabolic Wastes
 Like Urea , Uric Acid ,Creatinine
 To the Kidney , Skin and Intestine
 For their Removal

15. Functions of Blood
 Homeostatic for Water , pH and Electrolyte Concentration
 Blood forms Internal Environment of the Cell – “Millieu Interieur”
 In terms of Volume , Composition , Concentration , pH and Temperature
 Regulated to Normal Physiological Limits with respect to Minor Changes in the
Body
 This Mechanism is called “Homeostasis”
 Buffering Power of Haemoglobin “Helps to Maintain Constancy of Blood pH”

16. Functions of Blood
 Regulation of Body Temperature
 Blood preserves the very narrow range in body temperature
 Blood has water as major constituent which has :
 High specific heat - This buffers sudden change (rise or fall) in body temperature
 High conductivity - This helps to take out heat from an organ for uniform
distribution throughout the body
 High Latent Heat of Evaporation

17. Functions of Blood
 Chemical for Communication and Protection
 Concentration of Hormones and Various Substances in the Blood is regulated
through Feedback Mechanisms
 Within Blood Circulates the entire complex of Humoral Antibodies
 Important in Defence against Infection, Initiation of Inflammation and
Regulation of Haemostasis (Clotting Mechanism)

18. Functions of Blood
 Plasma Protein Functions
 Exerts the Osmotic Pressure which influences the Exchange of Fluid between
Blood and Tissues.
 Acts as a Reservoir of Proteins.
 Combines with many substances e.g Iron , Thyroxine and Steroid Hormones
 To form Transportable Complexes
 From which the Active Components are released at the Appropriate Sites

19. Serum
 If the Blood is allowed to Clot in a Test Tube, then the Clot Retracts and gives
out Serum
 Serum = Plasma – Fibrinogen – Clotting Factors (II , V and VIII)
 B’Coz these Factors get consumed during Clotting (Remaining do not)
 Serum has a Higher Serotonin (5-HydroxyTryptamine) Content
 Because of the Breakdown of Platelets during Clotting