Biology Notes: Blood and its Components

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.