Blood, Components of blood and Blood Groups:

What is  blood?

    • Blood is a transport fluid which is pushed by heart in the whole body to distribute oxygen and important It also collect carbon dioxide back to heart that is a type of waste material.
    • Blood cells are formed in bone marrow that is soft and spongy material present in the center of the bones.

What are different functions of Blood?

    • Nutrition transport: It transports oxygen and nutrients to every cell of the body.
    • Gas transport: It also take carbon dioxide back to lungs to get rid of it.
    • Coagulation of blood: It contains some substances that help to coagulate the blood.
    • Removal of waste products: It helps to carry waste products to liver and kidney so the body can get rid of it.
    • Protective function: It contains antibodies that makes the immune system strong.
    • Thermoregulation: It regulates the body temperature.
    • Regulation of different processes:
    • It also transports hormones to the target organs.
    • It also carries buffers that maintain the pH.
    • Osmotic function: It maintains osmotic pressure in blood vessels.
    • Detoxification: Blood enzymes split different toxic substances.

Is blood a tissue?

    • Blood is a connective tissue, composed of two parts:
    • Plasma (liquid part)
    • Blood cells: Red blood cells, White blood cells, platelets.

Components of plasma in blood

Yellowish- liquid containing:

    • Water 95%
    • Soluble proteins: fibrinogen, prothrombin, antibodies.
    • Dissolved mineral salts as ions: potassium, sodium and calcium.
    • Variables: products of digestion, vitamins, excretory products, hormones.
    • Dissolved gases: oxygen and carbon dioxide

Blood cells:

    • Red blood cells or Erythrocytes.
    • White blood cells or leukocytes.
    • Platelets or thrombocytes.

Formation of Red Blood Cells

Structure of a Red Blood Cell

How does a Red Blood Cell work?

White blood cells or leukocytes.

Platelets or thrombocytes:

    • Smallest cells of blood.
    • Cell fragments enclosed by a membrane.
    • Lack nucleus.
    • Platelets produce in bone marrow (spongy-like tissue)
    • Life-span between 5-9 days.
    • These cells play major role in blood coagulation and wound healing.
    • Platelets and damaged blood vessels at the wound release an enzyme known as thrombokinase which results in the production of
    • Thrombin acts on the plasma protein – (soluble protein)
    • Fibrinogen is converted into fibrin (insoluble protein) which forms a network of fibres like sieve.
    • These become clogged with red blood cells.
    • Stops further blood loss and stop harmful germs entering the body.

Red cells trapped in a fibrin network

The defense against infection by pathogens

Blood Groups:

    • Blood groups are named after the antigens present on red blood cells of every individual.
    • Red blood cells are covered by millions of antigens present on their membrane.
    • An antigen can be any substance to which immune system respond.
    • Antibodies are produced by WBCs (B lymphocytes) and used by immune system to identify and attack any foreign substances.
    • Antibodies are present in blood plasma.
    • Blood group Antigens are ignored by immune system but antigens of any other blood group will always be recognized as foreign particles and attacked by antibodies.
    • There are four blood groups – A, B, AB and O.
    • Antigens are represented by capital letters A and B
    • Antibodies may be represented by small letters a and b
    • The table below shows the antigens and antibodies present in the different blood groups:

    1. What happens when different blood groups are mixed?

Agglutination or blood clumping occurs

    1. What is the difference between positive and negative blood groups?

In some blood groups a protein RH factor is present on red blood cells called RH positive (positive blood groups) for example, O positive, A positive, AB positive etc.

And sometimes RH factor is absent on red blood cell so it is RH negative.

    1. Are all the blood antigens protein?

No blood antigens are either protein or sugar. For example antigens of ABO are sugars while antigens of RH blood group are proteins.

    1. What is immunization?

It is the process of production of antibodies in against of antigens.

    1. What is the difference between serum and plasma?

When blood clots, a yellowish liquid called serum is left behind, serum has the same composition as plasma except that it lacks the clotting factors.

    1. Which component of the blood makes the most of the volume of human blood?

Plasma is the most abundant substance in blood.

Red blood cells come on second number.

    1. What is the ratio of RBCs and WBCs?


    1. What is the life span of RBCs?

120 days

    1. What is the life span of WBCs?

Approximately 20-30 days

    1. Who is responsible for secreting thromboplastin?

Thromboplastin is secreted by platelets during the process of coagulation.

Test yourself:

    • What are the main components of blood?
    • What is another name of red blood cells?
    • What is another name of white blood cells?
    • What is another name of platelets?
    • What do you mean by agglutination?
    • What is the difference between granulocytes and agranulocytes?
    • Why red blood cells have no nucleus?
    • Why are red blood cells red in colour?
    • Where are red blood cells formed?
    • What is plasma?
    • Which are the cells responsible for making antibodies?
    • What is the difference between antigens and antibodies?
    • What is the difference between fibrinogen and fibrin?
    • What is phagocytosis?
    • Name the biggest WBC?