Jayanti Tokkas1, Shalini Jain2 and Hariom Yadav3*

1Department of Biochemistry, CCS HAU, Hisar, Haryana, India2Department of Biochemistry, Postgraduate Institute of Medical Education and

Research, Chandigarh, India3Nutritional Biotechnology, National Agri-Food Biotechnology Institute, Mohali, India

*Corresponding author: yadavhariom@gmail.com

BLOOD

Connective tissue in fluid form

Fluid of life – carries oxygen from lungs to all parts of body and carbon-di-oxide from all parts of the body to the lungs

Fluid of growth – carries nutritive substances from the digestive system and hormones from endocrine gland to all the tissues.

Fluid of health – protects the body against diseases and get rid of unwanted substances by transporting them into excretory organs like kidney.

Physical Characteristics of Blood

• Thicker than water

• 8 % of total body weight

• Blood volume» 70 mL/kg of body weight» 5 - 6 liters in males» 4 - 5 liters in females

• Temperature - 100.40F

• pH - 7.35 to 7.45

Blood Functions

1. Respiratory Transport O2 from lungs to tissues Transport CO2 from tissues to lungs

2. Nutrition Transport “food” from gut to tissues

3. Excretory Transport waste from tissues to kidney (urea,

uric acid)

4. Protective White blood cells , antibodies, antitoxins.

Blood Functions

5. Regulatory

regulate body temperature regulate pH through buffers coolant properties of water vasodilatation of surface vessels dump heat regulate water content of cells by interactions with dissolved

ions and proteins

6. Body Temperature Water- high heat capacity, thermal conductivity, heat of vaporization

Typical heat generation is 3000 kcal/day

Blood composition

Suspension of cells in plasma (carrier fluid)45% Cells 55% Plasma

Cells

Red cells (erythrocytes) 99% 5x106/mL

White cells (leukocytes)7x103/mL

< 1% Platelets (thrombocytes)

3x105/mL

Blood composition

Blood Plasma• Straw colored clear liquid • Contains 90% water• 7% plasma proteins

created in liverconfined to bloodstream

albuminmaintain blood osmotic pressure

immunoglobulinsantibodies bind to foreign

substances called antigens form antigen-antibody complexes

fibrinogen for clotting

• 2% other substances Nutrients, electrolytes, gases, hormones, waste products

Functions of plasma proteins

1. Coagulation of blood – Fibrinogen to fibrin

2. Defense mechanism of blood – Immunoglobulins

3. Transport mechanism – α Albumin, β globulin transport hormones, gases, enzymes, etc.

4. Maintenance of osmotic pressure in blood

5. Acid-base balance

6. Provides viscosity to blood

7. Provides suspension stability of RBC

8. Reserve proteins

Formed Elements of Blood• Red blood cells (R.B.C.)• White blood cells (W.B.C.)

granular leukocytes neutrophils eosinophils basophils

agranular leukocytes lymphocytes - T cells, B cells, natural killer cells

(N.K.C) monocytes

• Platelets (special cell fragments)

Functions of RBC

1. Transport oxygen from lungs to the tissues (oxyhemoglobin).

2. Transport carbon-di-oxide from tissues to lungs (carboxyhemoglobin)

3. Hemoglobin acts as a buffer and regulates the hydrogen ion concentration (acid base balance)

4. Carry the blood group antigens and Rh factor

Functions of neutrophils

1. First line of defence against invading micro-organisms.

2. Powerful and effective killer machine – contains enzymes like protease, elastase, metalloproteinase, NADPH oxidase; antibody like substances called defensins.

Defensins – antimicrobial peptides active against bacteria and fungi.

3.Secrete Platelet Aggregation Factor (PAF) – accelerates the aggregation of platelet during injury to the blood vessels

Functions of eosinophils

Secrete lethal substances at the time of exposure to foreign proteins/parasites

1. Eosinophill peroxidase – detroy worms, bacteria and tumor cells.

2. Major basic protein – damage parasites

3. Eosinophill cationic protein (ECP)- destroys helminths.

4. Eosinophill derived neurotoxin – destroys nerve fibres (myelinated nerve fibres)

Functions of basophils

Basophill granules release some important substances like –

1. Histamine – Acute hypersensitivity reaction- vascular changes, increase capillary permeability

2. Heparin – prevents intravascular blood clotting

3. Hyaluronic acid – necessary for deposition of ground substances in basement membrane

4. Proteases – exaggerate inflammation

• Basophill have IgE receptor – hypersensitivity reaction

Functions of Platelets

1.Blood clotting

2.Clot retraction

3.Defence mechanism

4.Homeostasis

5.Repair and rupture of blood vessel

Gas transport

• Continuous interchange of CO2 and O2 between lungs and tissues.

• Oxygen – • major e- acceptor• indispensable for ATP production.

• CO2 • major by product of energy metabolism

pH maintenance

• Oxygen release helps to maintain pH in tissues

• Lungs: – HHb + O2 = HbO2 + H+

• Tissues:

– CO2 forms proton and bicarbonate– Proton is bound to Hb, when O2 is released– Bicarbonate leaves RBC

• Cl- / HCO3- interchange - Hamburger effect

Hb

• Higher ability of Hb to release O2 but lower ability to bind O2 - Right shift

• Useful at site of O2 release (tissues)

• higher temperature

• higher 2,3 BPG level • lower pH (Bohr effect)

CO2 transport

1. Bicarbonate formation within RBC and Cl interchange

2. CO2 dissolved in blood plasma

3. Carbaminohemoglobin formation