Biology Notes: Blood and its Components

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Blood is a bodily fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. Blood contains antibodies, nutrients, oxygen and much more to help the bodywork. Let us have a look at the Composition of Human Blood in detail. The post is very important for upcoming Railways and SSC Exams 2023.

Human Blood

  • The blood constitutes 7% of the total weight of the human’s body.
  • Its pH value is nearly 7.4, so it is considered base in nature.
  • There is an average of 5-6 litres of blood in the human body.
  • Blood consists of two parts:-
    (1) Plasma
    (2) Blood Corpuscles

Components of Human Blood

(1) Plasma

  • It is the liquid part of blood.
  • It constitutes 60% part of the blood.
  • The plasma has 90% parts is water, 7% protein, 0.9% salt and 0.1% is glucose. 
  • Its main function is to Transport of digested food, hormones, the excretory product from one part of the body to another part of the body.
  • When Fibrinogen & Protein is extracted out of plasma, the remaining plasma is called serum.

(2) Blood Corpuscles

  • It constitutes 40% part of the blood/

This is divided into three parts:

1.Red Blood Corpuscles (RBC)

  • The nucleus is absent from it. Exception – Camel and Lama.
  • It is formed in Bone Marrow (At the embryonic stage its formation takes place in the liver.)
  • Lifespan- 20 days to 120 days.
  • RBCs destruction takes place in spleen so it is called grave of RBC.
  • It contains haemoglobin, in which haeme is iron-containing compound.
  • Due to the presence of haemoglobin colour of blood is red.
  • Globin is a proteinous compound which is extremely capable of combining with oxygen and carbon dioxide.
  • The iron compound found in haemoglobin is haematin.
  • Function- to carry oxygen to all cells of the body and bring back the carbon dioxide.
  • Anaemia disease is caused due to the deficiency of haemoglobin.
  • At the time of sleeping RBC is reduced by 5% and people who are at the height of 4200 metres RBC increases by 30% in them.

2. White Blood Corpuscles (WBC) or Leucocytes

  • Its formation takes place in Bone Marrow, lymph node and sometimes in liver and spleen.
  • Lifespan: 5-20 days.
  • The nucleus is present in the WBC.
  • Function- to protect the body from the disease.
  • The ratio of RBC and WBC is 600:1.
  • It consists of Granulocytes and Agranulocytes.
  • Granulocytes consists of Neutrophils, Eosinophils, and Basophils.
  • Agranulocytes consists of lymphocytes and monocytes.

3. Blood Platelets or Thrombocytes 

  • Found only in the blood of human and other mammals.
  • The nucleus is absent in it.
  • Its formation takes place in the Bone marrow.
  • Lifespan- 3 to 5 days.
  • It dies in the Spleen.
  • Function- to help in clotting of blood

Functions of Blood

  • To control the temperature of the body and to protect the body from diseases.
  • Transportation of oxygen, Carbon dioxide, digested food, conduction of hormones etc.
  • To help in establishing coordination among different parts.

Clotting of blood

  • Following reactions take place during clotting-
    (a) Thromboplastin + Prothrombin + Calcium = Thrombin
    (b) Thrombin + Fibrinogen = Fibrin
    (c) Fibrin + Blood Corpuscles = Clot
  • Vitamin K is helpful in blood clotting.

Blood Group of Human

  • Blood group was discovered by Landsteiner in 1900.
  • For this, he was awarded Nobel Prize in the year 1930.
  • The main reason behind the difference in the blood of the human is the glycoprotein which is found in Red Blood Corpuscles called an antigen.
  • The antigen is of two types- Antigen A and Antigen B.
  • On the basis of the presence of Antigen or Glyco Protein, there is four groups of blood in human:
  • That contains Antigen A – Blood Group A.
  • That contains Antigen B– Blood Group B.
  • That contains both the Antigen A and B – Blood Group AB.
  • That contains neither of the Antigens- Blood Group O.
  • An opposite type of protein is found in blood plasma. This is called an antibody. This is also of two types- Antibody a and Antibody .
    Blood Group O is called the Universal Donor because it does not contain any antigen.
    Blood Group AB is called Universal Recipient because it does not contain any antibody
  • Heparin is an anti-coagulant which is present in the blood which assures smooth blood flow in the vessels.
That’s all from our side in this article.
All The Best !!!


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