Composition of Blood and Functions!DMLT,BMLT Notes of blood!RBC,WBC,Platelets Lecture lab technician

COMPOSITION OF BLOOD
Total blood volume: 5-6 litres (8% of body weight or 80 mL/kg body weight)
Specific gravity : 1050-1060
Viscosity : 4-5 times that of water
PH : 7.4 ± 0.05; alkaline
. If anticoagulated sample of blood is allowed to stand in a narrow tube, on settling it separates out into cells and plasma.
A. CELLS
The cellular elements of blood represents 45% of the total blood volume, called Packed Cell Volume (PCV) or Haematocrit. It includes:
1. Erythrocytes or Red Blood Corpuscles (RBC's)
Normal count: 5 million/µL (5 x 106/μL).
2. Leucocytes or White Blood Corpuscles (WBCs)
Normal count: 4,000-11,000/μL (4-11 × 103/μL).
A. Granulocyte
Neutrophil
Eosinophils
Basophils
B. Agranulocyte
Monocytes
Lymphocytes
3. Platelets or Thrombocytes
Normal count: 1.5-4 lacs/µL (0.15 - 0.4 × 106/μL).
µL was previouly called as cumm.
B. PLASMA
1. Plasma is a clear, straw coloured fluid portion of the blood and represents 55% of the total blood volume
(about 5% of body weight). It contains:
(i) 91% water; and
(ii) 9% solids. The solids comprise:
(a) 1% inorganic molecules, and (b) 8% organic molecules.
2. The major inorganic molecules are:
(i) Na+, Ca2+, Cl-, HCO3- (mainly extracellular).
(ii) K+, Mg2+, Cu2+, PO, Protein (mainly intracellular).
(iii) Fe2+, Fe3+.
3. Of 8% total organic molecules:
(i) 7% are plasma proteins; and
(ii) 1% are other substances like Non-protein Nitrogenous (NPN) substances, sugar, fats, enzymes and hormones.
Plasma Proteins
Normal value: 6.4-8.3 gm/dL
Components
1. 55% Albumin: 3-5 gm/dL (Average: 4.8 gm/dL)
2. 38% Globulin: 2-3 gm/dL
(Average: 2.3 gm/dL)
(i) 13% a-Globulin: 0.78-0.81 gm/dL
(ii) 14% ẞ-Globulin: 0.79-0.84 gm/dL
(iii) 11% y-Globulin: 0.66-0.70 gm/dL
A/G ratio; Albumin: Globulin:: 1.7:1
3. 7% Fibrinogen: 0.3 gm/dL
4. Prothrombin : 40 mg/dL
Non-Protein Nitrogenous (NPN) Substances
Normal: 28-40 mg/dL
These are derivatives of food and in parts are the waste products of tissue catabolism. These include:
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
Other Substances
These include:
1. Neutral fats (triglycerides): 30-150 mg/dL
2. Phospholipids e.g. Lecithin, sphingomyelin, cephalin etc.
: 150-300 mg/dL
3. Glucose (fasting) :- : 70-90 mg/dL
4. Cholesterol : 120-200 mg/dL
FUNCTIONS OF BLOOD
1. Respiratory: Blood transports oxygen from lungs to the tissues and of carbon-dioxide from the tissues to the lungs.
2. Nutritive: Blood conveys absorbed food materials, glucose, amino acids, fatty acids, vitamins, electrolytes and trace metals from the alimentary canal to the tissues for utilization and storage.
3. Excretory: Blood transports the metabolic wastes e.g. urea, uric acid, creatinine etc. to the kidney, skin and intestine for their removal.
4. 'Homeostatic' for water, pH and electrolyte concentration: Blood forms internal environment of the cell .
5. Regulation of body temperature: Blood preserves the very narrow range in body temperature. How?
Blood whose major constituent is water has:
i) High specific heat - This buffers sudden change (rise or fall) in body temperature.
(ii) High conductivity - This helps to take out heat from an organ for uniform distribution throughout the body.
(iii) High latent heat of evaporation.
6. Chemical for communication and protection
(i) Concentration of hormones and various substances in the blood is regulated through feedback mechanisms.
(ii) Within blood circulates the entire complex of humoral antibodies important in defence against infection, initiation of inflammation and regulation of Haemostasis (clotting mechanism).
7. Plasma protein functions
(i) Exerts the osmotic pressure which influences the exchange of fluid between blood and tissues.
(ii) Acts as a reservoir of proteins.
(iii) 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.
SERUM
If the blood is allowed to clot in a test tube, then the clot retracts and gives out serum. Therefore, serum is plasma minus fibrinogen and clotting factors (II, V and VIII), because these factors get consumed during clotting (remaining do not).
Serum has a higher serotonin (5 hydroxytryptamine 5HT) content because of the breakdown of platelets during clotting.

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