Human Blood and Blood Groups

Human Blood and Blood Groups


  • Blood is a fluid connective tissue.
  • The quantity of blood in the human body is 7% of the total weight.
  • The PH value of blood is 7.4.
  • There is an average of 5-6 litres of blood in the human body.
  • It fights infection and regulates body temperature.
  • Females contain half litre of blood less in comparison to male.
  • Blood cells are produced in bone marrow.
  • The main functions of the blood are to transport oxygen, carbon dioxide, water and nutrients, hormones around the blood.
  • Blood has three major components
  • Plasma 55%
  • Corpuscles 45%
  • Blood platelets (thrombocytes)


  • liquid portion of blood.
  • It constitutes for about 55% of our blood, 92% of it is water.
  • It main functions are
  • Maintaining blood pressure.
  • Volume to supply critical proteins for blood clotting and immunity.
  • Medium for exchange of vital minerals such as sodium and potassium.
  • Helps to maintain a proper PH(acid-base) balance in the body. 

Red blood corpuscles

  • RBCs are disc shaped cells containing hemoglobin, which gives red colour to the blood.
  • Amount of haemoglobin is 14/15.6gm/100 cc of blood (11-14 in women).
  • RBCs are produced in the spleen and liver in foetus and in the bone marrow.
  • Haemoglobin enables the cells to pick up and deliver oxygen to all parts of the body, then pickup carbon dioxide and remove it from tissues.
  • Life of RBC is 20dys-120days after which they are broken down in the spleen or liver.
  • Product of breakdown of haemoglobin is a pigment (yellow colour), called bilirubin.
  • They have no nucleus.
  • Disorders Of Red Blood Cells
  • Presence of more RBC causes polycythemia.
  • Less RBC in blood causes Anemia.
  • Nutritional Anemia : lack of iron in food.
  • Aplastic, hemolytic, microcytic anemia : sudden change in shape.
  • Pernicious Anemia : lack of folic acid, pyridoxine.
  • Microcytic anemia : improper supply of oxygen.
  • Sickle cell anemia : who are with malaria suffering.
  • Blood of most molluscs (marine animals like squids, oysters, snails, octopuses etc) is blue due to the presence of copper protein in hemocyanin.

White Blood Corpuscles

  • Also called leukocytes, rounded with a nucleus, far less numerous than RBCs (1:600).
  • Life span is 3-4 days.
  • It defends the body from infections (scavengers of the body) and provides immunity.
  • WBC have nuclei and are also made in bone marrow.
  • WBC are two types 
  • Granulocytes : basophils, eosinophils and neutrophils.
  • Agranulocytes : monocytes and lymphocytes.
  • Basophils : take up basic stains. Secretes an anticoagulant heparin, which prevents clots within the blood vessels.
  • Eosinophils : take up acidic stains. Assists in defence mechanisms.
  • Neutrophils : stains equally with both acidic and basic types. Most numerous of the WBC. Defence.
  • Monocytes : largest of all, Very motile, Defence.
  • Lymphocytes : 25% of WBC. Takes part in antigen and antibody formation.


  • responsible for clotting.
  • Also called thrombocytes. Formed in bone marrow, about 250,000 lakhs/cumm of blood life 8-10 days.
  • Lymph : plasma+WBC
  • Lymph forms a second circulatory system. It acts as a middle man between blood and tissue.
  • Spleen produces lymph. At the same time it also acts as the graveyard of lymph.

Blood Groups

  • Father of blood grouping : karlandsteiner. He discovered A,B and O blood groups in 1900.
  • Blood circulation was discovered by William Harvey.
  • Decastello and Sturli in 1902 discovered AB blood group.
  • Antigens: they are proteins and are found on the surface of RBCs. Antigens are A and B.
  • Antibodies : they are produced in lymph glands and present in blood plasma. Antibodies are A and B.
  • AB is a universal recipient.
  • O is a universal donor.
  • RH factor : it is based on RH antigen. A person can be Rh+ or Rh-.
  • Rh+ can receive blood from Rh- but no vice-versa.
  • Blood transfusion technique was first developed by James Blundell in 1825.
  • Wrong stability of blood leads to death (clumping).
  • Citrate phosphate dextrose is used to preserve blood in blood banks.
Blood groupAntigenAntibody Can donate toCan receive from
OA & BA, B, AB, OO
Blood Groups

Also Read


Circulatory System

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